merge fixes

35 files changed, 545 insertions, 234 deletions

diff --git a/src/libnest2d/include/libnest2d/geometry_traits_nfp.hpp b/src/libnest2d/include/libnest2d/geometry_traits_nfp.hpp
index 29a1ccd04..07b34f47d 100644
--- a/src/libnest2d/include/libnest2d/geometry_traits_nfp.hpp
+++ b/src/libnest2d/include/libnest2d/geometry_traits_nfp.hpp
@@ -281,9 +281,10 @@ inline NfpResult<RawShape> nfpConvexOnly(const RawShape& sh,
             // cos function. But with the quadrant info we can get the sign back
             int sign = q[0] == 1 || q[0] == 2 ? -1 : 1;
             
+            // supermerill: add safe-check for when two points are on the same position
             // If Ratio is an actual rational type, there is no precision loss
-            auto pcos1 = Ratio(lcos[0]) / lsq1 * sign * lcos[0];
-            auto pcos2 = Ratio(lcos[1]) / lsq2 * sign * lcos[1];
+            auto pcos1 = lsq1 != 0 ? Ratio(lcos[0]) / lsq1 * sign * lcos[0] : 1 * sign * lcos[0];
+            auto pcos2 = lsq2 != 0 ? Ratio(lcos[1]) / lsq2 * sign * lcos[1] : 1 * sign * lcos[1];
             
             return q[0] < 2 ? pcos1 < pcos2 : pcos1 > pcos2;
         }
diff --git a/src/libslic3r/AppConfig.cpp b/src/libslic3r/AppConfig.cpp
index 7ea96372c..60e02e626 100644
--- a/src/libslic3r/AppConfig.cpp
+++ b/src/libslic3r/AppConfig.cpp
@@ -9,15 +9,16 @@
 #include <vector>
 #include <stdexcept>
 
-#include <boost/filesystem/path.hpp>
+#include <boost/algorithm/string/predicate.hpp>
 #include <boost/filesystem/operations.hpp>
+#include <boost/filesystem/path.hpp>
+#include <boost/format/format_fwd.hpp>
+#include <boost/locale.hpp>
+#include <boost/log/trivial.hpp>
 #include <boost/nowide/cenv.hpp>
 #include <boost/nowide/fstream.hpp>
 #include <boost/property_tree/ini_parser.hpp>
 #include <boost/property_tree/ptree_fwd.hpp>
-#include <boost/algorithm/string/predicate.hpp>
-#include <boost/format/format_fwd.hpp>
-#include <boost/log/trivial.hpp>
 
 #ifdef WIN32
 //FIXME replace the two following includes with <boost/md5.hpp> after it becomes mainstream.
diff --git a/src/libslic3r/Config.hpp b/src/libslic3r/Config.hpp
index 5ecd25ff2..5c8058aef 100644
--- a/src/libslic3r/Config.hpp
+++ b/src/libslic3r/Config.hpp
@@ -305,6 +305,7 @@ public:
     enum FlagsConfigOption : uint32_t {
         FCO_PHONY = 1,
         FCO_EXTRUDER_ARRAY = 1 << 1,
+        FCO_PLACEHOLDER_TEMP = 1 << 2,
     };
 
     ConfigOption() : flags(uint32_t(0)) {}
diff --git a/src/libslic3r/Fill/FillConcentric.cpp b/src/libslic3r/Fill/FillConcentric.cpp
index c8616f42f..fd3270663 100644
--- a/src/libslic3r/Fill/FillConcentric.cpp
+++ b/src/libslic3r/Fill/FillConcentric.cpp
@@ -78,6 +78,8 @@ FillConcentricWGapFill::fill_surface_extrusion(
     const FillParams &params,
     ExtrusionEntitiesPtr &out) const {
 
+    double min_gapfill_area = double(params.flow.scaled_width()) * double(params.flow.scaled_width());
+    if (params.config != nullptr) min_gapfill_area = scale_d(params.config->gap_fill_min_area.get_abs_value(params.flow.width)) * double(params.flow.scaled_width());
     // Perform offset.
     Slic3r::ExPolygons expp = offset_ex(surface->expolygon, double(scale_(0 - 0.5 * this->get_spacing())));
     // Create the infills for each of the regions.
@@ -149,7 +151,7 @@ FillConcentricWGapFill::fill_surface_extrusion(
             for (const ExPolygon &ex : gaps_ex) {
                 //remove too small gaps that are too hard to fill.
                 //ie one that are smaller than an extrusion with width of min and a length of max.
-                if (ex.area() > min*max) {
+                if (ex.area() > min_gapfill_area) {
                     MedialAxis{ ex, coord_t(max), coord_t(min), coord_t(params.flow.height) }.build(polylines);
                 }
             }
diff --git a/src/libslic3r/Fill/FillGyroid.cpp b/src/libslic3r/Fill/FillGyroid.cpp
index 0ff0972c5..461fc0e62 100644
--- a/src/libslic3r/Fill/FillGyroid.cpp
+++ b/src/libslic3r/Fill/FillGyroid.cpp
@@ -168,8 +168,6 @@ void FillGyroid::_fill_surface_single(
     const double tolerance_old = std::min(this->get_spacing() / 2, FillGyroid::PatternTolerance) / unscaled(scaleFactor);
     const double tolerance_old2 = std::min(this->get_spacing() / 2, FillGyroid::PatternTolerance) * density_adjusted  / this->get_spacing();
     const double tolerance = params.config->get_computed_value("resolution_internal") * density_adjusted / this->get_spacing();
-    std::cout << "gyroid tolerance: " << tolerance_old << " == " << tolerance_old2 << " ? "<< tolerance << "\n";
-    std::cout << "this->get_spacing(): " << this->get_spacing() << " , scaleFactor= " << unscaled(scaleFactor) << " , min(spa, 0.2)= " << std::min(this->get_spacing() / 2, FillGyroid::PatternTolerance) << "\n";
 
     // generate pattern
     Polylines polylines = make_gyroid_waves(
diff --git a/src/libslic3r/Format/CWS.cpp b/src/libslic3r/Format/CWS.cpp
index b28a47f50..395be5044 100644
--- a/src/libslic3r/Format/CWS.cpp
+++ b/src/libslic3r/Format/CWS.cpp
@@ -2,6 +2,10 @@
 #include "libslic3r/PrintConfig.hpp"
 #include "libslic3r/Time.hpp"
 
+#include <boost/log/trivial.hpp>
+#include <boost/filesystem.hpp>
+#include <boost/filesystem/path.hpp>
+
 namespace Slic3r {
 
 using ConfMap = std::map<std::string, std::string>;
diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index d8c6d6285..6a4b0a97a 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -16,9 +16,10 @@
 
 #include <algorithm>
 #include <cstdlib>
+#include <map>
 #include <math.h>
+#include <unordered_set>
 #include <string_view>
-#include <map>
 
 #include <boost/algorithm/string.hpp>
 #include <boost/algorithm/string/find.hpp>
@@ -3338,12 +3339,16 @@ std::string GCode::extrude_loop(const ExtrusionLoop &original_loop, const std::s
         Point current_point = paths.front().first_point();
         Point next_point = paths.front().polyline.points[1];  // second point
 
+        gcode += ";" + GCodeProcessor::Wipe_Start_Tag + "\n";
         //extra wipe before the little move.
         if (EXTRUDER_CONFIG_WITH_DEFAULT(wipe_extra_perimeter, 0) > 0) {
             coordf_t wipe_dist = scale_(EXTRUDER_CONFIG_WITH_DEFAULT(wipe_extra_perimeter,0));
             ExtrusionPaths paths_wipe;
+            m_wipe.reset_path();
             for (int i = 0; i < paths.size(); i++) {
                 ExtrusionPath& path = paths[i];
+                if (wipe_dist > 0) {
+                    //first, we use the polyline for wipe_extra_perimeter
                 if (path.length() < wipe_dist) {
                     wipe_dist -= path.length();
                     paths_wipe.push_back(path);
@@ -3362,8 +3367,14 @@ std::string GCode::extrude_loop(const ExtrusionLoop &original_loop, const std::s
                     } else {
                         next_point = paths[0].first_point();
                     }
-                    break;
+                        m_wipe.path.append(path.polyline);
+                        m_wipe.path.clip_start(wipe_dist);
+                        wipe_dist -= path.length();
                 }
+                } else {
+                    //then, it's stored for the wipe on retract
+                    m_wipe.path.append(path.polyline);
+            }
             }
             //move
             for (ExtrusionPath& path : paths_wipe) {
@@ -3371,6 +3382,7 @@ std::string GCode::extrude_loop(const ExtrusionLoop &original_loop, const std::s
                     prev_point = current_point;
                     current_point = pt;
                     gcode += m_writer.travel_to_xy(this->point_to_gcode(pt), 0.0, config().gcode_comments ? "; extra wipe" : "");
+                    this->set_last_pos(pt);
                 }
             }
         }
@@ -3398,7 +3410,7 @@ std::string GCode::extrude_loop(const ExtrusionLoop &original_loop, const std::s
         Vec2d  current_pos = current_point.cast<double>();
         Vec2d  next_pos = next_point.cast<double>();
         Vec2d  vec_dist  = next_pos - current_pos;
-        double nd = scale_d(EXTRUDER_CONFIG_WITH_DEFAULT(nozzle_diameter,0));
+        const coordf_t nd = scale_d(EXTRUDER_CONFIG_WITH_DEFAULT(nozzle_diameter,0));
         double l2 = vec_dist.squaredNorm();
         // Shift by no more than a nozzle diameter.
         //FIXME Hiding the seams will not work nicely for very densely discretized contours!
@@ -3406,6 +3418,65 @@ std::string GCode::extrude_loop(const ExtrusionLoop &original_loop, const std::s
         pt.rotate(angle, current_point);
         // generate the travel move
         gcode += m_writer.travel_to_xy(this->point_to_gcode(pt), 0.0, "move inwards before travel");
+        this->set_last_pos(pt);
+        gcode += ";" + GCodeProcessor::Wipe_End_Tag + "\n";
+
+        // also shift the wipe on retract
+        if (m_wipe.enable) {
+            current_pos = pt.cast<double>();
+            //go to the inside (use clipper for easy shift)
+            Polygon original_polygon = original_loop.polygon();
+            Polygons polys = offset(original_polygon, (original_polygon.is_clockwise()?1:-1) * nd / 2);
+            //find nearest point
+            size_t best_poly_idx = 0;
+            size_t best_pt_idx = 0;
+            coordf_t best_sqr_dist = nd*nd*2;
+            for (size_t poly_idx = 0; poly_idx < polys.size(); poly_idx++) {
+                Polygon& poly = polys[poly_idx];
+                if (poly.is_clockwise() ^ original_polygon.is_clockwise())
+                    poly.reverse();
+                for (size_t pt_idx = 0; pt_idx < poly.points.size(); pt_idx++) {
+                    if (poly.points[pt_idx].distance_to_square(pt) < best_sqr_dist) {
+                        best_sqr_dist = poly.points[pt_idx].distance_to_square(pt);
+                        best_poly_idx = poly_idx;
+                        best_pt_idx = pt_idx;
+    }
+                }
+            }
+            if (best_sqr_dist == nd * nd * 2) {
+                //try to find an edge
+                for (size_t poly_idx = 0; poly_idx < polys.size(); poly_idx++) {
+                    Polygon& poly = polys[poly_idx];
+                    if (poly.is_clockwise() ^ original_polygon.is_clockwise())
+                        poly.reverse();
+                    poly.points.push_back(poly.points.front());
+                    for (size_t pt_idx = 0; pt_idx < poly.points.size()-1; pt_idx++) {
+                        if (Line{ poly.points[pt_idx], poly.points[pt_idx + 1] }.distance_to_squared(pt) < best_sqr_dist) {
+                            poly.points.insert(poly.points.begin() + pt_idx + 1, pt);
+                            best_sqr_dist = 0;
+                            best_poly_idx = poly_idx;
+                            best_pt_idx = pt_idx + 1;
+                            poly.points.erase(poly.points.end() - 1);
+                            break;
+                        }
+                    }
+                }
+            }
+            if (best_sqr_dist == nd * nd * 2) {
+                //can't find a path, use the old one
+                //BOOST_LOG_TRIVIAL(warning) << "Warn: can't find a proper path for wipe on retract. Layer " << m_layer_index << ", pos " << this->point_to_gcode(pt).x() << " : " << this->point_to_gcode(pt).y() << " !";
+            } else {
+                m_wipe.reset_path();
+                //get the points from here
+                Polygon& poly = polys[best_poly_idx];
+                for (size_t pt_idx = best_pt_idx; pt_idx < poly.points.size(); pt_idx++) {
+                    m_wipe.path.append(poly.points[pt_idx]);
+                }
+                for (size_t pt_idx = 0; pt_idx < best_pt_idx; pt_idx++) {
+                    m_wipe.path.append(poly.points[pt_idx]);
+                }
+            }
+        }
     }
 
     return gcode;
@@ -4330,40 +4401,49 @@ Polyline GCode::travel_to(std::string &gcode, const Point &point, ExtrusionRole
         this->origin in order to get G-code coordinates.  */
     Polyline travel { this->last_pos(), point };
 
-    // check / compute avoid_crossing_perimeters
-    bool will_cross_perimeter = this->can_cross_perimeter(travel);
     // check whether wipe could be disabled without causing visible stringing
     bool could_be_wipe_disabled = false;
 
+    //can use the avoid crossing algo?
+    bool can_avoid_cross_peri = m_config.avoid_crossing_perimeters
+        && !m_avoid_crossing_perimeters.disabled_once()
+        && m_avoid_crossing_perimeters.is_init()
+        && !(m_config.avoid_crossing_not_first_layer && this->on_first_layer());
+
+    // check / compute avoid_crossing_perimeters
+    bool will_cross_perimeter = this->can_cross_perimeter(travel, can_avoid_cross_peri);
+
     // if a retraction would be needed (with a low min_dist threshold), try to use avoid_crossing_perimeters to plan a
     // multi-hop travel path inside the configuration space
     if (will_cross_perimeter && this->needs_retraction(travel, role, scale_d(EXTRUDER_CONFIG_WITH_DEFAULT(nozzle_diameter, 0.4)) * 3)
-        && m_config.avoid_crossing_perimeters
-        && ! m_avoid_crossing_perimeters.disabled_once()
-        && m_avoid_crossing_perimeters.is_init()
-        && !(m_config.avoid_crossing_not_first_layer && this->on_first_layer())) {
+        && can_avoid_cross_peri) {
         travel = m_avoid_crossing_perimeters.travel_to(*this, point, &could_be_wipe_disabled);
     }
+    if(can_avoid_cross_peri)
+        will_cross_perimeter = this->can_cross_perimeter(travel, false);
 
     // check whether a straight travel move would need retraction
     bool needs_retraction = this->needs_retraction(travel, role);
+    if (m_config.only_retract_when_crossing_perimeters)
+        needs_retraction = needs_retraction && will_cross_perimeter;
 
     // Re-allow avoid_crossing_perimeters for the next travel moves
     m_avoid_crossing_perimeters.reset_once_modifiers();
 
     // generate G-code for the travel move
     if (needs_retraction) {
-        if (m_config.avoid_crossing_perimeters && could_be_wipe_disabled)
+        if (m_config.avoid_crossing_perimeters && could_be_wipe_disabled && EXTRUDER_CONFIG_WITH_DEFAULT(wipe_only_crossing, true))
             m_wipe.reset_path();
 
         Point last_post_before_retract = this->last_pos();
         gcode += this->retract();
         // When "Wipe while retracting" is enabled, then extruder moves to another position, and travel from this position can cross perimeters.
-        // Because of it, it is necessary to call avoid crossing perimeters for the path between previous last_post and last_post after calling retraction()
-        if (last_post_before_retract != this->last_pos() && m_config.avoid_crossing_perimeters) {
-            Polyline retract_travel = m_avoid_crossing_perimeters.travel_to(*this, last_post_before_retract);
-            append(retract_travel.points, travel.points);
-            travel = std::move(retract_travel);
+        if (last_post_before_retract != this->last_pos() && can_avoid_cross_peri) {
+            // Is the distance is short enough to just shortcut it?
+            if (last_post_before_retract.distance_to(this->last_pos()) > scale_d(EXTRUDER_CONFIG_WITH_DEFAULT(nozzle_diameter, 0.4)) * 2) {
+                // Because of it, it is necessary to redo the thing
+                travel = m_avoid_crossing_perimeters.travel_to(*this, point);
+            }
         }
     } else {
         // Reset the wipe path when traveling, so one would not wipe along an old path.
@@ -4471,7 +4551,7 @@ bool GCode::needs_retraction(const Polyline& travel, ExtrusionRole role /*=erNon
     return true;
 }
 
-bool GCode::can_cross_perimeter(const Polyline& travel)
+bool GCode::can_cross_perimeter(const Polyline& travel, bool offset)
 {
     if(m_layer != nullptr)
     if ( (m_config.only_retract_when_crossing_perimeters && m_config.fill_density.value > 0) || m_config.avoid_crossing_perimeters)
@@ -4490,13 +4570,13 @@ bool GCode::can_cross_perimeter(const Polyline& travel)
         //if (inside) {
             //contained inside at least one bb
             //construct m_layer_slices_offseted if needed
-            if (m_layer_slices_offseted.layer != m_layer) {
+            if (m_layer_slices_offseted.layer != m_layer && offset) {
                 m_layer_slices_offseted.layer = m_layer;
                 m_layer_slices_offseted.diameter = scale_t(EXTRUDER_CONFIG_WITH_DEFAULT(nozzle_diameter, 0.4));
-                m_layer_slices_offseted.slices = offset_ex(m_layer->lslices, - m_layer_slices_offseted.diameter * 1.5);
+                m_layer_slices_offseted.slices = offset_ex(m_layer->lslices, -m_layer_slices_offseted.diameter * 1.5f);
             }
             // test if a expoly contains the entire travel
-            for (const ExPolygon &poly : m_layer_slices_offseted.slices)
+            for (const ExPolygon &poly : offset ? m_layer_slices_offseted.slices : m_layer->lslices)
                 if (poly.contains(travel)) {
                     return false;
                 }
@@ -4529,6 +4609,8 @@ std::string GCode::retract(bool toolchange)
         methods even if we performed wipe, since this will ensure the entire retraction
         length is honored in case wipe path was too short.  */
     gcode += toolchange ? m_writer.retract_for_toolchange() : m_writer.retract();
+
+    //check if need to lift
     bool need_lift = !m_writer.tool_is_extruder() || toolchange 
         || (BOOL_EXTRUDER_CONFIG(retract_lift_first_layer) && m_config.print_retract_lift.value != 0 && this->m_layer_index == 0) 
         || this->m_writer.get_extra_lift() > 0;
diff --git a/src/libslic3r/GCode.hpp b/src/libslic3r/GCode.hpp
index 7fab43e75..bfa644595 100644
--- a/src/libslic3r/GCode.hpp
+++ b/src/libslic3r/GCode.hpp
@@ -318,7 +318,7 @@ private:
 
     Polyline        travel_to(std::string& gcode, const Point &point, ExtrusionRole role);
     void            write_travel_to(std::string& gcode, const Polyline& travel, std::string comment);
-    bool            can_cross_perimeter(const Polyline& travel);
+    bool            can_cross_perimeter(const Polyline& travel, bool offset);
     bool            needs_retraction(const Polyline& travel, ExtrusionRole role = erNone, coordf_t max_min_dist = 0);
     std::string     retract(bool toolchange = false);
     std::string     unretract() { return m_writer.unlift() + m_writer.unretract(); }
diff --git a/src/libslic3r/GCode/AvoidCrossingPerimeters.cpp b/src/libslic3r/GCode/AvoidCrossingPerimeters.cpp
index 1d40a62bd..cad59bd32 100644
--- a/src/libslic3r/GCode/AvoidCrossingPerimeters.cpp
+++ b/src/libslic3r/GCode/AvoidCrossingPerimeters.cpp
@@ -9,6 +9,8 @@
 #include "../SVG.hpp"
 #include "AvoidCrossingPerimeters.hpp"
 
+#include <boost/log/trivial.hpp>
+
 #include <numeric>
 #include <unordered_set>
 
diff --git a/src/libslic3r/GCode/FanMover.cpp b/src/libslic3r/GCode/FanMover.cpp
index ca6db9ecf..6e138d1d2 100644
--- a/src/libslic3r/GCode/FanMover.cpp
+++ b/src/libslic3r/GCode/FanMover.cpp
@@ -242,6 +242,8 @@ void FanMover::_process_gcode_line(GCodeReader& reader, const GCodeReader::GCode
             if (fan_speed >= 0) {
                 const auto fan_baseline = (m_writer.config.fan_percentage.value ? 100.0 : 255.0);
                 fan_speed = 100 * fan_speed / fan_baseline;
+                //speed change: stop kickstart reverting if any
+                m_current_kickstart.time = -1;
                 if (!m_is_custom_gcode) {
                     // if slow down => put in the queue. if not =>
                     if (m_back_buffer_fan_speed < fan_speed) {
diff --git a/src/libslic3r/GCodeWriter.cpp b/src/libslic3r/GCodeWriter.cpp
index ede145d8d..09e45f1fe 100644
--- a/src/libslic3r/GCodeWriter.cpp
+++ b/src/libslic3r/GCodeWriter.cpp
@@ -1,10 +1,13 @@
 #include "GCodeWriter.hpp"
 #include "CustomGCode.hpp"
+
+#include <boost/lexical_cast.hpp>
+
 #include <algorithm>
+#include <assert.h>
 #include <iomanip>
 #include <iostream>
 #include <map>
-#include <assert.h>
 
 #define FLAVOR_IS(val) this->config.gcode_flavor.value == val
 #define FLAVOR_IS_NOT(val) this->config.gcode_flavor.value != val
diff --git a/src/libslic3r/MedialAxis.cpp b/src/libslic3r/MedialAxis.cpp
index c44c1d97a..02b4816e2 100644
--- a/src/libslic3r/MedialAxis.cpp
+++ b/src/libslic3r/MedialAxis.cpp
@@ -8,6 +8,9 @@
 #include "SVG.hpp"
 #include "polypartition.h"
 #include "poly2tri/poly2tri.h"
+
+#include <boost/log/trivial.hpp>
+
 #include <algorithm>
 #include <cassert>
 #include <list>
@@ -462,7 +465,7 @@ get_coeff_from_angle_countour(Point &point, const ExPolygon &contour, coord_t mi
     if (angle >= PI) angle = 2 * PI - angle;  // smaller angle
     //compute the diff from 90°
     angle = abs(angle - PI / 2);
-    if (point_near.coincides_with(point_nearest) && std::max(nearest_dist, near_dist) + SCALED_EPSILON < point_nearest.distance_to(point_near)) {
+    if (point_near.coincides_with_epsilon(point_nearest) && std::max(nearest_dist, near_dist) + SCALED_EPSILON < point_nearest.distance_to(point_near)) {
         //not only nearest
         Point point_before = id_near == 0 ? contour.contour.points.back() : contour.contour.points[id_near - 1];
         Point point_after = id_near == contour.contour.points.size() - 1 ? contour.contour.points.front() : contour.contour.points[id_near + 1];
@@ -499,7 +502,7 @@ MedialAxis::fusion_curve(ThickPolylines &pp)
 
         //check my length is small
         coord_t length = (coord_t)polyline.length();
-        if (length > max_width) continue;
+        if (length > this->max_width) continue;
 
         size_t closest_point_idx = this->expolygon.contour.closest_point_index(polyline.points.back());
 
@@ -529,13 +532,13 @@ MedialAxis::fusion_curve(ThickPolylines &pp)
         for (size_t j = 0; j < pp.size(); ++j) {
             if (j == i) continue;
             ThickPolyline& other = pp[j];
-            if (polyline.first_point().coincides_with(other.last_point())) {
+            if (polyline.first_point().coincides_with_epsilon(other.last_point())) {
                 other.reverse();
                 crosspoint.push_back(j);
                 double dot_temp = dot(Line(polyline.points[0], polyline.points[1]), (Line(other.points[0], other.points[1])));
                 min_dot = std::min(min_dot, abs(dot_temp));
                 sum_dot += dot_temp;
-            } else if (polyline.first_point().coincides_with(other.first_point())) {
+            } else if (polyline.first_point().coincides_with_epsilon(other.first_point())) {
                 crosspoint.push_back(j);
                 double dot_temp = dot(Line(polyline.points[0], polyline.points[1]), (Line(other.points[0], other.points[1])));
                 min_dot = std::min(min_dot, abs(dot_temp));
@@ -604,7 +607,7 @@ MedialAxis::remove_bits(ThickPolylines &pp)
 
         //check my length is small
         coordf_t length = polyline.length();
-        if (length > coordf_t(max_width) * 1.5) {
+        if (length > coordf_t(this->max_width) * 1.5) {
             continue;
         }
 
@@ -613,10 +616,10 @@ MedialAxis::remove_bits(ThickPolylines &pp)
         for (size_t j = 0; j < pp.size(); ++j) {
             if (j == i) continue;
             ThickPolyline& other = pp[j];
-            if (polyline.first_point().coincides_with(other.last_point())) {
+            if (polyline.first_point().coincides_with_epsilon(other.last_point())) {
                 other.reverse();
                 crosspoint.push_back(j);
-            } else if (polyline.first_point().coincides_with(other.first_point())) {
+            } else if (polyline.first_point().coincides_with_epsilon(other.first_point())) {
                 crosspoint.push_back(j);
             }
         }
@@ -631,11 +634,11 @@ MedialAxis::remove_bits(ThickPolylines &pp)
         if (nb_better_than_me < 2) continue;
 
         //check if the length of the polyline is small vs width of the other lines
-        coord_t max_width = 0;
+        coord_t local_max_width = 0;
         for (int i = 0; i < crosspoint.size(); i++) {
-            max_width = std::max(max_width, pp[crosspoint[i]].width[0]);
+            local_max_width = std::max(local_max_width, pp[crosspoint[i]].width[0]);
         }
-        if (length > coordf_t(max_width + min_width))
+        if (length > coordf_t(local_max_width + min_width))
             continue;
 
         //delete the now unused polyline
@@ -665,17 +668,17 @@ MedialAxis::fusion_corners(ThickPolylines &pp)
 
         //check my length is small
         coord_t length = (coord_t)polyline.length();
-        if (length > max_width) continue;
+        if (length > this->max_width) continue;
 
         // look if other end is a cross point with multiple other branch
         std::vector<size_t> crosspoint;
         for (size_t j = 0; j < pp.size(); ++j) {
             if (j == i) continue;
             ThickPolyline& other = pp[j];
-            if (polyline.first_point().coincides_with(other.last_point())) {
+            if (polyline.first_point().coincides_with_epsilon(other.last_point())) {
                 other.reverse();
                 crosspoint.push_back(j);
-            } else if (polyline.first_point().coincides_with(other.first_point())) {
+            } else if (polyline.first_point().coincides_with_epsilon(other.first_point())) {
                 crosspoint.push_back(j);
             }
         }
@@ -764,7 +767,7 @@ MedialAxis::extends_line(ThickPolyline& polyline, const ExPolygons& anchors, con
         // prevent the line from touching on the other side, otherwise intersection() might return that solution
         if (polyline.points.size() == 2 && this->expolygon.contains(line.midpoint())) line.a = line.midpoint();
 
-        line.extend_end((double)max_width);
+        line.extend_end((double)this->max_width);
         Point new_back;
         if (this->expolygon.contour.has_boundary_point(polyline.points.back())) {
             new_back = polyline.points.back();
@@ -842,14 +845,14 @@ MedialAxis::extends_line(ThickPolyline& polyline, const ExPolygons& anchors, con
         }*/
         // find anchor
         Point best_anchor;
-        coordf_t shortest_dist = (coordf_t)max_width;
+        coordf_t shortest_dist = (coordf_t)this->max_width;
         for (const ExPolygon& a : anchors) {
             Point p_maybe_inside = a.contour.centroid();
             coordf_t test_dist = new_bound.distance_to(p_maybe_inside) + new_back.distance_to(p_maybe_inside);
             //if (test_dist < max_width / 2 && (test_dist < shortest_dist || shortest_dist < 0)) {
             double angle_test = new_back.ccw_angle(p_maybe_inside, line.a);
             if (angle_test > PI) angle_test = 2 * PI - angle_test;
-            if (test_dist < max_width && test_dist<shortest_dist && abs(angle_test) > PI / 2) {
+            if (test_dist < (coordf_t)this->max_width && test_dist<shortest_dist && abs(angle_test) > PI / 2) {
                 shortest_dist = test_dist;
                 best_anchor = p_maybe_inside;
             }
@@ -859,7 +862,7 @@ MedialAxis::extends_line(ThickPolyline& polyline, const ExPolygons& anchors, con
             p_obj.x() /= 2;
             p_obj.y() /= 2;
             Line l2 = Line(new_back, p_obj);
-            l2.extend_end((double)max_width);
+            l2.extend_end((coordf_t)this->max_width);
             (void)bounds->contour.first_intersection(l2, &new_bound);
         }
         if (new_bound.coincides_with_epsilon(new_back))
@@ -909,13 +912,13 @@ MedialAxis::main_fusion(ThickPolylines& pp)
             // find another polyline starting here
             for (size_t j = i + 1; j < pp.size(); ++j) {
                 ThickPolyline& other = pp[j];
-                if (polyline.last_point().coincides_with(other.last_point())) {
+                if (polyline.last_point().coincides_with_epsilon(other.last_point())) {
                     polyline.reverse();
                     other.reverse();
-                } else if (polyline.first_point().coincides_with(other.last_point())) {
+                } else if (polyline.first_point().coincides_with_epsilon(other.last_point())) {
                     other.reverse();
-                } else if (polyline.first_point().coincides_with(other.first_point())) {
-                } else if (polyline.last_point().coincides_with(other.first_point())) {
+                } else if (polyline.first_point().coincides_with_epsilon(other.first_point())) {
+                } else if (polyline.last_point().coincides_with_epsilon(other.first_point())) {
                     polyline.reverse();
                 } else {
                     continue;
@@ -936,10 +939,10 @@ MedialAxis::main_fusion(ThickPolylines& pp)
                 if (
                     ((polyline.points.back().distance_to(other.points.back())
                     + (polyline.width.back() + other.width.back()) / 4)
-                > max_width*1.05))
+                > this->max_width *1.05))
                     continue;
                 // test if the lines are not too different in length.
-                if (abs(polyline.length() - other.length()) > max_width) continue;
+                if (abs(polyline.length() - other.length()) > (coordf_t)this->max_width) continue;
 
 
                 //test if we don't merge with something too different and without any relevance.
@@ -955,7 +958,7 @@ MedialAxis::main_fusion(ThickPolylines& pp)
                 //    << (abs(polyline.length()*coeffSizePolyI - other.length()*coeffSizeOtherJ) > max_width / 2)
                 //    << (abs(polyline.length()*coeffSizePolyI - other.length()*coeffSizeOtherJ) > max_width)
                 //    << "\n";
-                if (abs(polyline.length()*coeffSizePolyI - other.length()*coeffSizeOtherJ) > max_width / 2) continue;
+                if (abs(polyline.length()*coeffSizePolyI - other.length()*coeffSizeOtherJ) > (coordf_t)(this->max_width / 2)) continue;
 
 
                 //compute angle to see if it's better than previous ones (straighter = better).
@@ -975,7 +978,7 @@ MedialAxis::main_fusion(ThickPolylines& pp)
                     //std::cout << "try to find main : " << k << " ? " << i << " " << j << " ";
                     if (k == i || k == j) continue;
                     ThickPolyline& main = pp[k];
-                    if (polyline.first_point().coincides_with(main.last_point())) {
+                    if (polyline.first_point().coincides_with_epsilon(main.last_point())) {
                         main.reverse();
                         if (!main.endpoints.second)
                             find_main_branch = true;
@@ -983,7 +986,7 @@ MedialAxis::main_fusion(ThickPolylines& pp)
                             biggest_main_branch_id = k;
                             biggest_main_branch_length = (coord_t)main.length();
                         }
-                    } else if (polyline.first_point().coincides_with(main.first_point())) {
+                    } else if (polyline.first_point().coincides_with_epsilon(main.first_point())) {
                         if (!main.endpoints.second)
                             find_main_branch = true;
                         else if (biggest_main_branch_length < main.length()) {
@@ -1111,8 +1114,8 @@ MedialAxis::main_fusion(ThickPolylines& pp)
                     //std::cout << "width:" << polyline.width[idx_point] << " = " << value_from_current_width << " + " << value_from_dist 
                     //    << " (<" << max_width << " && " << (bounds.contour.closest_point(polyline.points[idx_point])->distance_to(polyline.points[idx_point]) * 2.1)<<")\n";
                     //failsafes
-                    if (polyline.width[idx_point] > max_width)
-                        polyline.width[idx_point] = max_width;
+                    if (polyline.width[idx_point] > this->max_width)
+                        polyline.width[idx_point] = this->max_width;
                     //failsafe: try to not go out of the radius of the section, take the width of the merging point for that. (and with some offset)
                     coord_t main_branch_width = pp[biggest_main_branch_id].width.front();
                     coordf_t main_branch_dist = pp[biggest_main_branch_id].points.front().distance_to(polyline.points[idx_point]);
@@ -1249,7 +1252,7 @@ MedialAxis::remove_too_thin_extrusion(ThickPolylines& pp)
             changes = true;
         }
         //remove points and bits that comes from a "main line"
-        if (polyline.points.size() < 2 || (changes && polyline.length() < max_width && polyline.points.size() ==2)) {
+        if (polyline.points.size() < 2 || (changes && polyline.length() < this->max_width && polyline.points.size() ==2)) {
             //remove self if too small
             pp.erase(pp.begin() + i);
             --i;
@@ -1288,14 +1291,14 @@ MedialAxis::concatenate_polylines_with_crossing(ThickPolylines& pp)
             if (other.endpoints.first && other.endpoints.second) continue;
             bool me_reverse = false;
             bool other_reverse = false;
-            if (polyline.last_point().coincides_with(other.last_point())) {
+            if (polyline.last_point().coincides_with_epsilon(other.last_point())) {
                 other_reverse = true;
-            } else if (polyline.first_point().coincides_with(other.last_point())) {
+            } else if (polyline.first_point().coincides_with_epsilon(other.last_point())) {
                 me_reverse = true;
                 other_reverse = true;
-            } else if (polyline.first_point().coincides_with(other.first_point())) {
+            } else if (polyline.first_point().coincides_with_epsilon(other.first_point())) {
                 me_reverse = true;
-            } else if (!polyline.last_point().coincides_with(other.first_point())) {
+            } else if (!polyline.last_point().coincides_with_epsilon(other.first_point())) {
                 continue;
             }
 
@@ -1313,12 +1316,12 @@ MedialAxis::concatenate_polylines_with_crossing(ThickPolylines& pp)
             }
         }
         if (best_candidate != nullptr && best_candidate->points.size() > 1) {
-            if (polyline.last_point().coincides_with(best_candidate->last_point())) {
+            if (polyline.last_point().coincides_with_epsilon(best_candidate->last_point())) {
                 best_candidate->reverse();
-            } else if (polyline.first_point().coincides_with(best_candidate->last_point())) {
+            } else if (polyline.first_point().coincides_with_epsilon(best_candidate->last_point())) {
                 polyline.reverse();
                 best_candidate->reverse();
-            } else if (polyline.first_point().coincides_with(best_candidate->first_point())) {
+            } else if (polyline.first_point().coincides_with_epsilon(best_candidate->first_point())) {
                 polyline.reverse();
             }
             //intersections may create over-extrusion because the included circle can be a bit larger. We have to make it short again if needed.
@@ -1327,8 +1330,12 @@ MedialAxis::concatenate_polylines_with_crossing(ThickPolylines& pp)
                     && polyline.width.back() > best_candidate->width[1]) {
                 polyline.width.back() = std::min(polyline.width[polyline.width.size() - 2], best_candidate->width[1]);
             }
-            polyline.points.insert(polyline.points.end(), best_candidate->points.begin() + 1, best_candidate->points.end());
-            polyline.width.insert(polyline.width.end(), best_candidate->width.begin() + 1, best_candidate->width.end());
+            //be far enough
+            int far_idx = 1;
+            while (far_idx < best_candidate->points.size() && polyline.last_point().coincides_with_epsilon(best_candidate->points[far_idx]))
+                far_idx++;
+            polyline.points.insert(polyline.points.end(), best_candidate->points.begin() + far_idx, best_candidate->points.end());
+            polyline.width.insert(polyline.width.end(), best_candidate->width.begin() + far_idx, best_candidate->width.end());
             polyline.endpoints.second = best_candidate->endpoints.second;
             assert(polyline.width.size() == polyline.points.size());
             if (best_idx < i) i--;
@@ -1412,18 +1419,18 @@ MedialAxis::remove_too_short_polylines(ThickPolylines& pp, const coord_t min_siz
     //    if (endpoint_not_used[idx_endpoint]) {
     //        int nb_endpoints;
     //        Point pt = idx_endpoint % 2 == 0 ? polyline.first_point() : polyline.last_point();
-    //        if (idx_endpoint % 2 == 0 && pt.coincides_with(polyline.last_point())) {
+    //        if (idx_endpoint % 2 == 0 && pt.coincides_with_epsilon(polyline.last_point())) {
     //            nb_endpoints++;
     //            endpoint_not_used[(idx_endpoint / 2) + 1] = false;
     //        }
     //        //good, now find other points
     //        for (size_t idx_other_pp = (idx_endpoint / 2) + 1; idx_other_pp < pp.size(); idx_other_pp++) {
     //            ThickPolyline& other = pp[idx_other_pp];
-    //            if (pt.coincides_with(other.first_point())) {
+    //            if (pt.coincides_with_epsilon(other.first_point())) {
     //                nb_endpoints++;
     //                endpoint_not_used[idx_other_pp * 2] = false;
     //            }
-    //            if (pt.coincides_with(other.last_point())) {
+    //            if (pt.coincides_with_epsilon(other.last_point())) {
     //                nb_endpoints++;
     //                endpoint_not_used[idx_other_pp * 2 + 1] = false;
     //            }
@@ -1435,7 +1442,7 @@ MedialAxis::remove_too_short_polylines(ThickPolylines& pp, const coord_t min_siz
     //        std::cout << "reduce " << reduction << " points!\n";
     //        if (idx_endpoint % 2 == 0 ) {
     //            polyline.width.front() *= reduction;
-    //            if(pt.coincides_with(polyline.last_point()))
+    //            if(pt.coincides_with_epsilon(polyline.last_point()))
     //                polyline.width.back() *= reduction;
     //        } else {
     //            polyline.width.back() *= reduction;
@@ -1443,10 +1450,10 @@ MedialAxis::remove_too_short_polylines(ThickPolylines& pp, const coord_t min_siz
     //        //good, now find other points
     //        for (size_t idx_other_pp = (idx_endpoint / 2) + 1; idx_other_pp < pp.size(); idx_other_pp++) {
     //            ThickPolyline& other = pp[idx_other_pp];
-    //            if (pt.coincides_with(other.first_point())) {
+    //            if (pt.coincides_with_epsilon(other.first_point())) {
     //                other.width.front() *= reduction;
     //            }
-    //            if (pt.coincides_with(other.last_point())) {
+    //            if (pt.coincides_with_epsilon(other.last_point())) {
     //                other.width.back() *= reduction;
     //            }
     //        }
@@ -1468,17 +1475,15 @@ MedialAxis::remove_too_short_polylines(ThickPolylines& pp, const coord_t min_siz
             // know how long will the endpoints be extended since it depends on polygon thickness
             // which is variable - extension will be <= max_width/2 on each side) 
             if ((polyline.endpoints.first || polyline.endpoints.second)) {
-                coordf_t max_width = max_width / 2;
+                coordf_t local_max_width = this->max_width / 2;
                 for (coordf_t w : polyline.width)
-                    max_width = std::max(max_width, w);
-                if(polyline.length() < max_width) {
+                    local_max_width = std::max(local_max_width, w);
+                if(polyline.length() < local_max_width) {
                     if (shortest_size > polyline.length()) {
                         shortest_size = polyline.length();
                         shortest_idx = i;
                     }
-
                 }
-
             }
         }
         if (shortest_idx < pp.size()) {
@@ -1490,14 +1495,14 @@ MedialAxis::remove_too_short_polylines(ThickPolylines& pp, const coord_t min_siz
 }
 
 void
-MedialAxis::check_width(ThickPolylines& pp, coord_t max_width, std::string msg)
+MedialAxis::check_width(ThickPolylines& pp, coord_t local_max_width, std::string msg)
 {
     //remove empty polyline
     int nb = 0;
     for (size_t i = 0; i < pp.size(); ++i) {
         for (size_t j = 0; j < pp[i].width.size(); ++j) {
-            if (pp[i].width[j] > coord_t(max_width * 1.01)) {
-                BOOST_LOG_TRIVIAL(error) << "Error " << msg << " width " << unscaled(pp[i].width[j]) << "(" << i << ":" << j << ") > " << unscaled(max_width) << "\n";
+            if (pp[i].width[j] > coord_t(local_max_width * 1.01)) {
+                BOOST_LOG_TRIVIAL(error) << "Error " << msg << " width " << unscaled(pp[i].width[j]) << "(" << i << ":" << j << ") > " << unscaled(local_max_width) << "\n";
                 nb++;
             }
         }
@@ -1696,7 +1701,7 @@ MedialAxis::build(ThickPolylines &polylines_out)
 {
     //static int id = 0;
     //id++;
-    //std::cout << this->id << "\n";
+    //std::cout << id << "\n";
     //{
     //    std::stringstream stri;
     //    stri << "medial_axis_0_enter_" << id << ".svg";
@@ -1709,8 +1714,8 @@ MedialAxis::build(ThickPolylines &polylines_out)
     //    std::stringstream stri;
     //    stri << "medial_axis_0.5_simplified_" << id << ".svg";
     //    SVG svg(stri.str());
-    //    svg.draw(bounds);
-    //    svg.draw(this->expolygon);
+    //    svg.draw(*bounds, "grey");
+    //    svg.draw(this->expolygon, "green");
     //    svg.Close();
     //}
     //safety check
@@ -1777,9 +1782,9 @@ MedialAxis::build(ThickPolylines &polylines_out)
     //    std::stringstream stri;
     //    stri << "medial_axis_0.9_voronoi_" << id << ".svg";
     //    SVG svg(stri.str());
-    //    //svg.draw(bounds);
-    //    svg.draw(this->expolygon);
-    //    svg.draw(pp);
+    //    svg.draw(*bounds, "grey");
+    //    svg.draw(this->expolygon, "green");
+    //    svg.draw(pp, "red");
     //    svg.Close();
     //}
 
@@ -1798,15 +1803,33 @@ MedialAxis::build(ThickPolylines &polylines_out)
         //    pp.erase(pp.begin() + tp_idx);
         //    --tp_idx;
         //}
+        //voronoi problem: can put two consecutive points at the same position. Delete one.
+        for (size_t i = 1; i < tp.points.size()-1; i++) {
+            if (tp.points[i-1].distance_to_square(tp.points[i]) < SCALED_EPSILON) {
+                tp.points.erase(tp.points.begin() + i);
+                tp.width.erase(tp.width.begin() + i);
+                i--;
+            }
+        }
+        //delete the inner one
+        if (tp.points.size()>2 && tp.points[tp.points.size() - 2].distance_to_square(tp.points.back()) < SCALED_EPSILON) {
+            tp.points.erase(tp.points.end() - 2);
+            tp.width.erase(tp.width.end() - 2);
+        }
+        //delete null-length polylines
+        if (tp.length() < SCALED_EPSILON && tp.first_point().coincides_with_epsilon(tp.last_point())) {
+            pp.erase(pp.begin() + tp_idx);
+            --tp_idx;
+        }
     }
     //std::cout << "polyline_from_voronoi\n";
     //{
     //    std::stringstream stri;
     //    stri << "medial_axis_1_voronoi_" << id << ".svg";
     //    SVG svg(stri.str());
-    //    svg.draw(*bounds);
-    //    svg.draw(this->expolygon);
-    //    svg.draw(pp);
+    //    svg.draw(*bounds, "grey");
+    //    svg.draw(this->expolygon, "green");
+    //    svg.draw(pp, "red");
     //    svg.Close();
     //}
 
@@ -1819,9 +1842,9 @@ MedialAxis::build(ThickPolylines &polylines_out)
     //    std::stringstream stri;
     //    stri << "medial_axis_1_voronoi_" << id << ".svg";
     //    SVG svg(stri.str());
-    //    svg.draw(*bounds);
-    //    svg.draw(this->expolygon);
-    //    svg.draw(pp);
+    //    svg.draw(*bounds, "grey");
+    //    svg.draw(this->expolygon, "green");
+    //    svg.draw(pp, "red");
     //    svg.Close();
     //}
 
@@ -1845,9 +1868,9 @@ MedialAxis::build(ThickPolylines &polylines_out)
     //    std::stringstream stri;
     //    stri << "medial_axis_2_curve_" << id << ".svg";
     //    SVG svg(stri.str());
-    //    svg.draw(*bounds);
-    //    svg.draw(this->expolygon);
-    //    svg.draw(pp);
+    //    svg.draw(*bounds, "grey");
+    //    svg.draw(this->expolygon, "green");
+    //    svg.draw(pp, "red");
     //    svg.Close();
     //}
 
@@ -1862,9 +1885,9 @@ MedialAxis::build(ThickPolylines &polylines_out)
     //    std::stringstream stri;
     //    stri << "medial_axis_3_fusion_" << id << ".svg";
     //    SVG svg(stri.str());
-    //    svg.draw(bounds);
-    //    svg.draw(this->expolygon);
-    //    svg.draw(pp);
+    //    svg.draw(*bounds, "grey");
+    //    svg.draw(this->expolygon, "green");
+    //    svg.draw(pp, "red");
     //    svg.Close();
     //}
 
@@ -1874,6 +1897,15 @@ MedialAxis::build(ThickPolylines &polylines_out)
     // Loop through all returned polylines in order to extend their endpoints to the 
     //   expolygon boundaries (if done here, it may be cut later if not thick enough)
     if (stop_at_min_width) {
+        //{
+        //    std::stringstream stri;
+        //    stri << "medial_axis_3_3_extends_" << id << ".svg";
+        //    SVG svg(stri.str());
+        //    svg.draw(*bounds, "grey");
+        //    svg.draw(this->expolygon, "green");
+        //    svg.draw(pp, "red");
+        //    svg.Close();
+        //}
         extends_line_both_side(pp);
     }
 
@@ -1885,14 +1917,24 @@ MedialAxis::build(ThickPolylines &polylines_out)
         std::cout << "\n";
     }*/
     //reduce extrusion when it's too thin to be printable
+    //{
+    //    std::stringstream stri;
+    //    stri << "medial_axis_3_6_remove_thin_" << id << ".svg";
+    //    SVG svg(stri.str());
+    //    svg.draw(*bounds, "grey");
+    //    svg.draw(this->expolygon, "green");
+    //    svg.draw(pp, "red");
+    //    svg.Close();
+    //}
+
     remove_too_thin_extrusion(pp);
     //{
     //    std::stringstream stri;
     //    stri << "medial_axis_4_thinok_" << id << ".svg";
     //    SVG svg(stri.str());
-    //    svg.draw(bounds);
-    //    svg.draw(this->expolygon);
-    //    svg.draw(pp);
+    //    svg.draw(*bounds, "grey");
+    //    svg.draw(this->expolygon, "green");
+    //    svg.draw(pp, "red");
     //    svg.Close();
     //}
 
@@ -1901,9 +1943,9 @@ MedialAxis::build(ThickPolylines &polylines_out)
     //    std::stringstream stri;
     //    stri << "medial_axis_5.0_thuinner_" << id << ".svg";
     //    SVG svg(stri.str());
-    //    svg.draw(*bounds);
-    //    svg.draw(this->expolygon);
-    //    svg.draw(pp);
+    //    svg.draw(*bounds, "grey");
+    //    svg.draw(this->expolygon, "green");
+    //    svg.draw(pp, "red");
     //    svg.Close();
     //}
 
@@ -1916,9 +1958,9 @@ MedialAxis::build(ThickPolylines &polylines_out)
     //    std::stringstream stri;
     //    stri << "medial_axis_5_expand_" << id << ".svg";
     //    SVG svg(stri.str());
-    //    svg.draw(*bounds);
-    //    svg.draw(this->expolygon);
-    //    svg.draw(pp);
+    //    svg.draw(*bounds, "grey");
+    //    svg.draw(this->expolygon, "green");
+    //    svg.draw(pp, "red");
     //    svg.Close();
     //}
     //TODO: reduce the flow at the intersection ( + ) points on crossing?
@@ -1927,9 +1969,9 @@ MedialAxis::build(ThickPolylines &polylines_out)
     //    std::stringstream stri;
     //    stri << "medial_axis_6_concat_" << id << ".svg";
     //    SVG svg(stri.str());
-    //    svg.draw(bounds);
-    //    svg.draw(this->expolygon);
-    //    svg.draw(pp);
+    //    svg.draw(*bounds, "grey");
+    //    svg.draw(this->expolygon, "green");
+    //    svg.draw(pp, "red");
     //    svg.Close();
     //}
 
@@ -1938,9 +1980,9 @@ MedialAxis::build(ThickPolylines &polylines_out)
     //    std::stringstream stri;
     //    stri << "medial_axis_8_tooshort_" << id << ".svg";
     //    SVG svg(stri.str());
-    //    svg.draw(bounds);
-    //    svg.draw(this->expolygon);
-    //    svg.draw(pp);
+    //    svg.draw(*bounds, "grey");
+    //    svg.draw(this->expolygon, "green");
+    //    svg.draw(pp, "red");
     //    svg.Close();
     //}
 
@@ -1949,9 +1991,9 @@ MedialAxis::build(ThickPolylines &polylines_out)
     //    std::stringstream stri;
     //    stri << "medial_axis_9.1_end_" << id << ".svg";
     //    SVG svg(stri.str());
-    //    svg.draw(*bounds);
-    //    svg.draw(this->expolygon);
-    //    svg.draw(pp);
+    //    svg.draw(*bounds, "grey");
+    //    svg.draw(this->expolygon, "green");
+    //    svg.draw(pp, "red");
     //    svg.Close();
     //}
     if (nozzle_diameter != min_width) {
@@ -1964,9 +2006,9 @@ MedialAxis::build(ThickPolylines &polylines_out)
     //    std::stringstream stri;
     //    stri << "medial_axis_9.9_endnwithtaper_" << id << ".svg";
     //    SVG svg(stri.str());
-    //    svg.draw(*bounds);
-    //    svg.draw(this->expolygon);
-    //    svg.draw(pp);
+    //    svg.draw(*bounds, "grey");
+    //    svg.draw(this->expolygon, "green");
+    //    svg.draw(pp, "red");
     //    svg.Close();
     //}
 
@@ -2058,8 +2100,11 @@ thin_variable_width(const ThickPolylines &polylines, ExtrusionRole role, Flow fl
                     continue;
                 }
             } else if (i > 0 && resolution_internal > line_len + prev_line_len) {
-                ThickLine& prev_line = lines[i - 1];
                 //merge lines?
+                //if it's a loop, merge only if the distance is high enough
+                if (p.first_point() == p.last_point() && p.length() < (line_len + prev_line_len) * 6)
+                    continue;
+                ThickLine& prev_line = lines[i - 1];
                 coordf_t width = prev_line_len * (prev_line.a_width + prev_line.b_width) / 2;
                 width += line_len * (line.a_width + line.b_width) / 2;
                 prev_line.b = line.b;
@@ -2129,13 +2174,14 @@ thin_variable_width(const ThickPolylines &polylines, ExtrusionRole role, Flow fl
                     path.height = flow.height;
                 }
             }
+            assert(path.polyline.points.size() > 2 || path.first_point() != path.last_point());
         }
         if (path.polyline.is_valid())
             paths.emplace_back(std::move(path));
 
         // Append paths to collection.
         if (!paths.empty()) {
-            if (paths.front().first_point().coincides_with(paths.back().last_point())) {
+            if (paths.front().first_point().coincides_with_epsilon(paths.back().last_point())) {
                 coll.append(ExtrusionLoop(paths));
             } else {
                 if (role == erThinWall){
diff --git a/src/libslic3r/PerimeterGenerator.cpp b/src/libslic3r/PerimeterGenerator.cpp
index 6ba0c0815..aba01cfd1 100644
--- a/src/libslic3r/PerimeterGenerator.cpp
+++ b/src/libslic3r/PerimeterGenerator.cpp
@@ -462,7 +462,7 @@ void PerimeterGenerator::process()
             // In case no perimeters are to be generated, loop_number will equal to -1.            
             std::vector<PerimeterGeneratorLoops> contours(loop_number + 1);    // depth => loops
             std::vector<PerimeterGeneratorLoops> holes(loop_number + 1);       // depth => loops
-            ThickPolylines thin_walls;
+            ThickPolylines thin_walls_thickpolys;
             ExPolygons no_last_gapfill;
             // we loop one time more than needed in order to find gaps after the last perimeter was applied
             for (int i = 0;; ++i) {  // outer loop is 0
@@ -492,15 +492,15 @@ void PerimeterGenerator::process()
                         next_onion = offset_ex(
                             last,
                             -(float)(ext_perimeter_width / 2),
-                            (round_peri ? ClipperLib::JoinType::jtRound : ClipperLib::JoinType::jtMiter),
-                            (round_peri ? min_round_spacing : 3));
+                            ClipperLib::JoinType::jtMiter,
+                            3);
                     else
                         next_onion = offset2_ex(
                             last,
                             -(float)(ext_perimeter_width / 2 + ext_min_spacing / 2 - 1),
                             +(float)(ext_min_spacing / 2 - 1),
-                            (round_peri ? ClipperLib::JoinType::jtRound : ClipperLib::JoinType::jtMiter),
-                            (round_peri ? min_round_spacing : 3));
+                            ClipperLib::JoinType::jtMiter,
+                            3);
 
                     // look for thin walls
                     if (this->config->thin_walls) {
@@ -562,27 +562,27 @@ void PerimeterGenerator::process()
                                         ma.use_bounds(bound)
                                             .use_min_real_width(scale_t(this->ext_perimeter_flow.nozzle_diameter))
                                             .use_tapers(thin_walls_overlap)
-                                            .build(thin_walls);
+                                            .build(thin_walls_thickpolys);
                                     }
                                     break;
                                 }
                             }
                         }
                         // use perimeters to extrude area that can't be printed by thin walls
-                        // it's a bit like re-add thin area in to perimeter area.
+                        // it's a bit like re-add thin area into perimeter area.
                         // it can over-extrude a bit, but it's for a better good.
                         {
                             if (thin_perimeter)
                                 next_onion = union_ex(next_onion, offset_ex(diff_ex(last, thins, true),
                                     -(float)(ext_perimeter_width / 2),
-                                    (round_peri ? ClipperLib::JoinType::jtRound : ClipperLib::JoinType::jtMiter),
-                                    (round_peri ? min_round_spacing : 3)));
+                                    ClipperLib::JoinType::jtMiter,
+                                    3));
                             else
                                 next_onion = union_ex(next_onion, offset2_ex(diff_ex(last, thins, true),
                                     -(float)((ext_perimeter_width / 2) + (ext_min_spacing / 4)),
                                     (float)(ext_min_spacing / 4),
-                                    (round_peri ? ClipperLib::JoinType::jtRound : ClipperLib::JoinType::jtMiter),
-                                    (round_peri ? min_round_spacing : 3)));
+                                    ClipperLib::JoinType::jtMiter,
+                                    3));
 
                             next_onion = intersection_ex(next_onion, last);
                         }
@@ -937,20 +937,23 @@ void PerimeterGenerator::process()
                 }
 
                 // append thin walls
-                if (!thin_walls.empty()) {
-                    ExtrusionEntityCollection tw = thin_variable_width
-                    (thin_walls, erThinWall, this->ext_perimeter_flow, std::max(ext_perimeter_width/4, scale_t(this->print_config->resolution)));
-
-                    entities.append(tw.entities);
-                    thin_walls.clear();
+                if (!thin_walls_thickpolys.empty()) {
+                    if (this->object_config->thin_walls_merge) {
+                        _merge_thin_walls(entities, thin_walls_thickpolys);
+                    } else {
+                        ExtrusionEntityCollection tw = thin_variable_width
+                            (thin_walls_thickpolys, erThinWall, this->ext_perimeter_flow, std::max(ext_perimeter_width / 4, scale_t(this->print_config->resolution)));
+                        entities.append(tw.entities);
+                    }
+                    thin_walls_thickpolys.clear();
                 }
             } else {
                 if (this->object_config->thin_walls_merge) {
                     ThickPolylines no_thin_walls;
                     entities = this->_traverse_loops(contours.front(), no_thin_walls);
-                    _merge_thin_walls(entities, thin_walls);
+                    _merge_thin_walls(entities, thin_walls_thickpolys);
                 } else {
-                    entities = this->_traverse_loops(contours.front(), thin_walls);
+                    entities = this->_traverse_loops(contours.front(), thin_walls_thickpolys);
                 }
             }
 
@@ -1697,11 +1700,12 @@ void PerimeterGenerator::_merge_thin_walls(ExtrusionEntityCollection &extrusions
             } else {
                 //first add the return path
                 ExtrusionEntityCollection tws_second = tws;
-                tws_second.reverse();
                 change_flow.percent_extrusion = 0.1f;
                 change_flow.use(tws_second);
+                //force reverse
                 for (ExtrusionPath &path : change_flow.paths)
                     path.reverse();
+                std::reverse(change_flow.paths.begin(), change_flow.paths.end());
                 //std::reverse(change_flow.paths.begin(), change_flow.paths.end());
                 searcher.search_result.loop->paths.insert(searcher.search_result.loop->paths.begin() + 1 + searcher.search_result.idx_path,
                     change_flow.paths.begin(), change_flow.paths.end());
diff --git a/src/libslic3r/PlaceholderParser.cpp b/src/libslic3r/PlaceholderParser.cpp
index c077d6cd7..26f77b1ca 100644
--- a/src/libslic3r/PlaceholderParser.cpp
+++ b/src/libslic3r/PlaceholderParser.cpp
@@ -1,11 +1,13 @@
 #include "PlaceholderParser.hpp"
 #include "Exception.hpp"
 #include "Flow.hpp"
+
 #include <cstring>
 #include <ctime>
 #include <iomanip>
 #include <sstream>
 #include <map>
+
 #ifdef _MSC_VER
     #include <stdlib.h>  // provides **_environ
 #else
@@ -25,6 +27,7 @@
 #endif
 
 #include <boost/algorithm/string.hpp>
+#include <boost/log/trivial.hpp>
 #include <boost/nowide/convert.hpp>
 
 // Spirit v2.5 allows you to suppress automatic generation
@@ -649,6 +652,8 @@ namespace client
         bool                     just_boolean_expression = false;
         std::string              error_message;
 
+        static std::map<t_config_option_key, std::unique_ptr<ConfigOption>> checked_vars;
+
         // Table to translate symbol tag to a human readable error message.
         static std::map<std::string, std::string> tag_to_error_message;
 
@@ -663,6 +668,11 @@ namespace client
                 opt = config->option(opt_key);
             if (opt == nullptr && external_config != nullptr)
                 opt = external_config->option(opt_key);
+            if (opt == nullptr) {
+                auto it = MyContext::checked_vars.find(opt_key);
+                if (it != MyContext::checked_vars.end())
+                    opt = it->second.get();
+            }
             return opt;
         }
 
@@ -822,12 +832,52 @@ namespace client
             boost::iterator_range<Iterator> &opt_key,
             OptWithPos<Iterator>            &output)
         {
-            const ConfigOption *opt = ctx->resolve_symbol(std::string(opt_key.begin(), opt_key.end()));
+            std::string str_key = std::string(opt_key.begin(), opt_key.end());
+            const ConfigOption *opt = ctx->resolve_symbol(str_key);
             if (opt == nullptr)
                 ctx->throw_exception("Not a variable name", opt_key);
             output.opt = opt;
             output.it_range = opt_key;
         }
+        
+        // function to check if a var exist & add a dummy var if not
+        template <typename Iterator>
+        static void check_variable(
+            const MyContext* ctx,
+            boost::iterator_range<Iterator>& opt_key,
+            Iterator& end_pos,
+            expr<Iterator>& out,
+            ConfigOption* default_val = nullptr)
+        {
+            t_config_option_key key = std::string(opt_key.begin(), opt_key.end());
+            const ConfigOption* opt = nullptr;
+            if (ctx->config_override != nullptr)
+                opt = ctx->config_override->option(key);
+            if (opt == nullptr)
+                opt = ctx->config->option(key);
+            if (opt == nullptr && ctx->external_config != nullptr)
+                opt = ctx->external_config->option(key);
+            if (opt == nullptr) {
+                std::unique_ptr<ConfigOption> ppt;
+                if(default_val == nullptr)
+                    ppt = std::unique_ptr<ConfigOption>(new ConfigOptionBool(false));
+                else
+                    ppt = std::unique_ptr<ConfigOption>(default_val);
+                // set flag to say "it's a var that isn't here, please ignore it"
+                ppt->flags |= ConfigOption::FCO_PLACEHOLDER_TEMP;
+                if (MyContext::checked_vars.find(key) != MyContext::checked_vars.end()) {
+                    if (default_val != nullptr) {
+                        // erase previous value
+                        MyContext::checked_vars[key] = std::move(ppt);
+                    }
+                } else {
+                    // put the var
+                    MyContext::checked_vars.emplace(std::move(key), std::move(ppt));
+                }
+            }
+            //return
+            out = expr<Iterator>(opt != nullptr, out.it_range.begin(), end_pos);
+        }
 
         template <typename Iterator>
         static void scalar_variable_reference(
@@ -941,8 +991,11 @@ namespace client
             Iterator                         it_end,
             expr<Iterator>                  &output)
         {
-            if (opt.opt->is_scalar())
+            if (opt.opt->is_scalar()) {
+                if (0 != (opt.opt->flags & ConfigOption::FCO_PLACEHOLDER_TEMP)) // fake var, from checked_vars
+                    return scalar_variable_reference(ctx, opt, output);
                 ctx->throw_exception("Referencing a scalar variable when vector is expected", opt.it_range);
+            }
             const ConfigOptionVectorBase *vec = static_cast<const ConfigOptionVectorBase*>(opt.opt);
             if (vec->empty())
                 ctx->throw_exception("Indexing an empty vector variable", opt.it_range);
@@ -1061,6 +1114,7 @@ namespace client
         { "variable_reference",         "Expecting a variable reference."},
         { "regular_expression",         "Expecting a regular expression."}
     };
+    std::map<t_config_option_key, std::unique_ptr<ConfigOption>> MyContext::checked_vars = {};
 
     // For debugging the boost::spirit parsers. Print out the string enclosed in it_range.
     template<typename Iterator>
@@ -1321,6 +1375,15 @@ namespace client
                         { out = value.unary_not(out.it_range.begin()); }
                 static void to_int(expr<Iterator> &value, expr<Iterator> &out)
                         { out = value.unary_integer(out.it_range.begin()); }
+                //function for default keyword
+                static void default_bool_(bool &value, const MyContext* ctx, boost::iterator_range<Iterator>& opt_key, Iterator& end_pos, expr<Iterator>& out)
+                        { MyContext::check_variable<Iterator>(ctx, opt_key, end_pos, out, new ConfigOptionBool(value)); }
+                static void default_int_(int &value, const MyContext* ctx, boost::iterator_range<Iterator>& opt_key, Iterator& end_pos, expr<Iterator>& out)
+                        { MyContext::check_variable<Iterator>(ctx, opt_key, end_pos, out, new ConfigOptionInt(value)); }
+                static void default_double_(double &value, const MyContext* ctx, boost::iterator_range<Iterator>& opt_key, Iterator& end_pos, expr<Iterator>& out)
+                        { MyContext::check_variable<Iterator>(ctx, opt_key, end_pos, out, new ConfigOptionFloat(value)); }
+                static void default_string_(boost::iterator_range<Iterator>& it_range, const MyContext* ctx, boost::iterator_range<Iterator>& opt_key, Iterator& end_pos, expr<Iterator>& out)
+                        { MyContext::check_variable<Iterator>(ctx, opt_key, end_pos, out, new ConfigOptionString(std::string(it_range.begin() + 1, it_range.end() - 1))); }
             };
             unary_expression = iter_pos[px::bind(&FactorActions::set_start_pos, _1, _val)] >> (
                     scalar_variable_reference(_r1)                  [ _val = _1 ]
@@ -1335,6 +1398,15 @@ namespace client
                 |   (kw["random"] > '(' > conditional_expression(_r1) [_val = _1] > ',' > conditional_expression(_r1) > ')') 
                                                                     [ px::bind(&MyContext::random<Iterator>, _r1, _val, _2) ]
                 |   (kw["int"] > '(' > unary_expression(_r1) > ')') [ px::bind(&FactorActions::to_int,  _1,     _val) ]
+                |   (kw["exists"] > '('  > identifier > ')' > iter_pos)        [ px::bind(&MyContext::check_variable<Iterator>, _r1, _1, _2, _val, nullptr) ]
+                |   (kw["default"] > '(' > identifier > ',' > strict_double > ')' > iter_pos)
+                                                                    [px::bind(&FactorActions::default_double_, _2, _r1, _1, _3, _val)]
+                |   (kw["default"] > '(' > identifier > ',' > int_ > ')' > iter_pos)
+                                                                    [px::bind(&FactorActions::default_int_, _2, _r1, _1, _3, _val)]
+                |   (kw["default"] > '('  > identifier > ',' > kw[bool_] > ')' > iter_pos)
+                                                                    [ px::bind(&FactorActions::default_bool_, _2, _r1, _1, _3, _val) ]
+                |   (kw["default"] > '(' > identifier > ',' > raw[lexeme['"' > *((utf8char - char_('\\') - char_('"')) | ('\\' > char_)) > '"']] > ')' > iter_pos)
+                                                                    [px::bind(&FactorActions::default_string_, _2, _r1, _1, _3, _val)]
                 |   (strict_double > iter_pos)                      [ px::bind(&FactorActions::double_, _1, _2, _val) ]
                 |   (int_      > iter_pos)                          [ px::bind(&FactorActions::int_,    _1, _2, _val) ]
                 |   (kw[bool_] > iter_pos)                          [ px::bind(&FactorActions::bool_,   _1, _2, _val) ]
@@ -1373,7 +1445,9 @@ namespace client
                 ("random")
                 ("not")
                 ("or")
-                ("true");
+                ("true")
+                ("exists")
+                ("default");
 
             if (0) {
                 debug(start);
@@ -1499,11 +1573,11 @@ void PlaceholderParser::append_custom_variables(std::map<std::string, std::vecto
 
     bool is_array = nb_extruders > 0;
     if (!is_array) nb_extruders = 1;
-    std::regex is_a_name("[a-zA-Z_]+");
+    SLIC3R_REGEX_NAMESPACE::regex is_a_name("[a-zA-Z_]+");
     for (const auto& entry : name2var_array) {
         if (entry.first.empty())
             continue;
-        if (!std::regex_match(entry.first, is_a_name))
+        if (!SLIC3R_REGEX_NAMESPACE::regex_match(entry.first, is_a_name))
             continue;
         const std::vector<std::string>& values = entry.second;
         //check if all values are empty
@@ -1552,7 +1626,7 @@ void PlaceholderParser::append_custom_variables(std::map<std::string, std::vecto
         //check if all values are numeric
         bool is_not_numeric = !is_not_string || !is_not_bool;
         std::vector<double> double_values;
-        //std::regex("\\s*[+-]?([0-9]+\\.[0-9]*([Ee][+-]?[0-9]+)?|\\.[0-9]+([Ee][+-]?[0-9]+)?|[0-9]+[Ee][+-]?[0-9]+)");
+        //SLIC3R_REGEX_NAMESPACE::regex("\\s*[+-]?([0-9]+\\.[0-9]*([Ee][+-]?[0-9]+)?|\\.[0-9]+([Ee][+-]?[0-9]+)?|[0-9]+[Ee][+-]?[0-9]+)");
         if (!is_not_numeric) {
             for (int extruder_id = 0; extruder_id < nb_extruders; ++extruder_id) {
                 if (!values[extruder_id].empty()) {
diff --git a/src/libslic3r/Point.hpp b/src/libslic3r/Point.hpp
index aaf1e7e48..b6a511b88 100644
--- a/src/libslic3r/Point.hpp
+++ b/src/libslic3r/Point.hpp
@@ -155,7 +155,7 @@ public:
     double distance_to(const Line &line) const;
     bool coincides_with(const Point &point) const { return this->x() == point.x() && this->y() == point.y(); }
     bool coincides_with_epsilon(const Point &point) const {
-        return std::abs(this->x() - point.x()) < SCALED_EPSILON && std::abs(this->y() - point.y()) < SCALED_EPSILON;
+        return std::abs(this->x() - point.x()) < SCALED_EPSILON/2 && std::abs(this->y() - point.y()) < SCALED_EPSILON/2;
     }
 };
 
diff --git a/src/libslic3r/Polyline.cpp b/src/libslic3r/Polyline.cpp
index 8f294f162..c7cf15c75 100644
--- a/src/libslic3r/Polyline.cpp
+++ b/src/libslic3r/Polyline.cpp
@@ -273,7 +273,7 @@ void concatThickPolylines(ThickPolylines& pp) {
         //concat polyline if only 2 polyline at a point
         for (size_t i = 0; i < pp.size(); ++i) {
             ThickPolyline *polyline = &pp[i];
-            if (polyline->first_point().coincides_with(polyline->last_point())) {
+            if (polyline->first_point().coincides_with_epsilon(polyline->last_point())) {
                 polyline->endpoints.first = false;
                 polyline->endpoints.second = false;
                 continue;
@@ -287,25 +287,25 @@ void concatThickPolylines(ThickPolylines& pp) {
             for (size_t j = 0; j < pp.size(); ++j) {
                 if (j == i) continue;
                 ThickPolyline *other = &pp[j];
-                if (polyline->last_point().coincides_with(other->last_point())) {
+                if (polyline->last_point().coincides_with_epsilon(other->last_point())) {
                     id_candidate_last_point = j;
                     nbCandidate_last_point++;
                 }
-                if (polyline->last_point().coincides_with(other->first_point())) {
+                if (polyline->last_point().coincides_with_epsilon(other->first_point())) {
                     id_candidate_last_point = j;
                     nbCandidate_last_point++;
                 }
-                if (polyline->first_point().coincides_with(other->last_point())) {
+                if (polyline->first_point().coincides_with_epsilon(other->last_point())) {
                     id_candidate_first_point = j;
                     nbCandidate_first_point++;
                 }
-                if (polyline->first_point().coincides_with(other->first_point())) {
+                if (polyline->first_point().coincides_with_epsilon(other->first_point())) {
                     id_candidate_first_point = j;
                     nbCandidate_first_point++;
                 }
             }
             if (id_candidate_last_point == id_candidate_first_point && nbCandidate_first_point == 1 && nbCandidate_last_point == 1) {
-                if (polyline->first_point().coincides_with(pp[id_candidate_first_point].first_point())) pp[id_candidate_first_point].reverse();
+                if (polyline->first_point().coincides_with_epsilon(pp[id_candidate_first_point].first_point())) pp[id_candidate_first_point].reverse();
                 // it's a trap! it's a  loop!
                 polyline->points.insert(polyline->points.end(), pp[id_candidate_first_point].points.begin() + 1, pp[id_candidate_first_point].points.end());
                 polyline->width.insert(polyline->width.end(), pp[id_candidate_first_point].width.begin() + 1, pp[id_candidate_first_point].width.end());
@@ -316,7 +316,7 @@ void concatThickPolylines(ThickPolylines& pp) {
             } else {
 
                 if (nbCandidate_first_point == 1) {
-                    if (polyline->first_point().coincides_with(pp[id_candidate_first_point].first_point())) pp[id_candidate_first_point].reverse();
+                    if (polyline->first_point().coincides_with_epsilon(pp[id_candidate_first_point].first_point())) pp[id_candidate_first_point].reverse();
                     //concat at front
                     polyline->width[0] = std::max(polyline->width.front(), pp[id_candidate_first_point].width.back());
                     polyline->points.insert(polyline->points.begin(), pp[id_candidate_first_point].points.begin(), pp[id_candidate_first_point].points.end() - 1);
@@ -336,7 +336,7 @@ void concatThickPolylines(ThickPolylines& pp) {
                     polyline->endpoints.first = true;
                 }
                 if (nbCandidate_last_point == 1) {
-                    if (polyline->last_point().coincides_with(pp[id_candidate_last_point].last_point())) pp[id_candidate_last_point].reverse();
+                    if (polyline->last_point().coincides_with_epsilon(pp[id_candidate_last_point].last_point())) pp[id_candidate_last_point].reverse();
                     //concat at back
                     polyline->width[polyline->width.size() - 1] = std::max(polyline->width.back(), pp[id_candidate_last_point].width.front());
                     polyline->points.insert(polyline->points.end(), pp[id_candidate_last_point].points.begin() + 1, pp[id_candidate_last_point].points.end());
@@ -353,7 +353,7 @@ void concatThickPolylines(ThickPolylines& pp) {
                     polyline->endpoints.second = true;
                 }
 
-                if (polyline->last_point().coincides_with(polyline->first_point())) {
+                if (polyline->last_point().coincides_with_epsilon(polyline->first_point())) {
                     //the concat has created a loop : update endpoints
                     polyline->endpoints.first = false;
                     polyline->endpoints.second = false;
diff --git a/src/libslic3r/Preset.cpp b/src/libslic3r/Preset.cpp
index 30ce2a8c0..eefb4f4bb 100644
--- a/src/libslic3r/Preset.cpp
+++ b/src/libslic3r/Preset.cpp
@@ -710,7 +710,7 @@ const std::vector<std::string>& Preset::filament_options()
         "filament_retract_length", "filament_retract_lift", "filament_retract_lift_above", "filament_retract_lift_below", "filament_retract_speed", "filament_deretract_speed", "filament_retract_restart_extra", "filament_retract_before_travel",
         "filament_retract_layer_change", "filament_retract_before_wipe", 
         "filament_seam_gap",
-        "filament_wipe", "filament_wipe_extra_perimeter", "filament_wipe_speed",
+        "filament_wipe", "filament_wipe_only_crossing", "filament_wipe_extra_perimeter", "filament_wipe_speed",
         // Profile compatibility
         "filament_vendor", "compatible_prints", "compatible_prints_condition", "compatible_printers", "compatible_printers_condition", "inherits"
         //merill adds
diff --git a/src/libslic3r/Print.cpp b/src/libslic3r/Print.cpp
index c5841ceea..2394adbb7 100644
--- a/src/libslic3r/Print.cpp
+++ b/src/libslic3r/Print.cpp
@@ -196,6 +196,7 @@ bool Print::invalidate_state_by_config_options(const std::vector<t_config_option
         "use_volumetric_e",
         "variable_layer_height",
         "wipe",
+        "wipe_only_crossing",
         "wipe_speed",
         "wipe_extra_perimeter"
     };
@@ -1644,7 +1645,7 @@ std::pair<PrintBase::PrintValidationError, std::string> Print::validate() const
                     //check not-first layer
                     if (object->region_volumes[region_id].front().first.second > layer_height) {
                         if (layer_height + EPSILON < min_layer_height)
-                            return { PrintBase::PrintValidationError::pveWrongSettings, (boost::format(L("First layer height can't be higher than %s")) % "min layer height").str() };
+                            return { PrintBase::PrintValidationError::pveWrongSettings, (boost::format(L("Layer height can't be higher than %s")) % "min layer height").str() };
                         for (auto tuple : std::vector<std::pair<double, const char*>>{
                                 {nozzle_diameter, "nozzle diameter"},
                                 {max_layer_height, "max layer height"},
diff --git a/src/libslic3r/PrintBase.cpp b/src/libslic3r/PrintBase.cpp
index e4a0b45cc..5ca0198d5 100644
--- a/src/libslic3r/PrintBase.cpp
+++ b/src/libslic3r/PrintBase.cpp
@@ -4,6 +4,8 @@
 #include <boost/filesystem.hpp>
 #include <boost/lexical_cast.hpp>
 
+#include <regex>
+
 #include "I18N.hpp"
 
 //! macro used to mark string used at localization, 
diff --git a/src/libslic3r/PrintConfig.cpp b/src/libslic3r/PrintConfig.cpp
index d50cbecf8..de22a6689 100644
--- a/src/libslic3r/PrintConfig.cpp
+++ b/src/libslic3r/PrintConfig.cpp
@@ -138,7 +138,7 @@ void PrintConfigDef::init_common_params()
     def = this->add("slice_closing_radius", coFloat);
     def->label = L("Slice gap closing radius");
     def->category = OptionCategory::slicing;
-    def->tooltip = L("Cracks smaller than 2x gap closing radius are being filled during the triangle mesh slicing. "
+    def->tooltip = L("Fill cracks smaller than 2x gap closing radius during the triangle mesh slicing. "
                      "The gap closing operation may reduce the final print resolution, therefore it is advisable to keep the value reasonably low.");
     def->sidetext = L("mm");
     def->min = 0;
@@ -223,7 +223,7 @@ void PrintConfigDef::init_fff_params()
     def->label = L("Allow empty layers");
     def->full_label = L("Allow empty layers");
     def->category = OptionCategory::slicing;
-    def->tooltip = L("Do not prevent the gcode builder to trigger an exception if a full layer is empty and so the print will have to start from thin air afterward.");
+    def->tooltip = L("Prevent the gcode builder from triggering an exception if a full layer is empty, and allow the print to start from thin air afterward.");
     def->mode = comExpert;
     def->set_default_value(new ConfigOptionBool(false));
 
@@ -240,7 +240,7 @@ void PrintConfigDef::init_fff_params()
     def->label = L("Don't avoid crossing on 1st layer");
     def->full_label = L("Don't avoid crossing on 1st layer");
     def->category = OptionCategory::perimeter;
-    def->tooltip = L("Do not use the 'Avoid crossing perimeters' on the first layer.");
+    def->tooltip = L("Disable 'Avoid crossing perimeters' for the first layer.");
     def->mode = comExpert;
     def->set_default_value(new ConfigOptionBool(true));
 
@@ -249,7 +249,7 @@ void PrintConfigDef::init_fff_params()
     def->category = OptionCategory::perimeter;
     def->tooltip = L("The maximum detour length for avoid crossing perimeters. "
                      "If the detour is longer than this value, avoid crossing perimeters is not applied for this travel path. "
-                     "Detour length could be specified either as an absolute value or as percentage (for example 50%) of a direct travel path.");
+                     "Detour length can be specified either as an absolute value or as percentage (for example 50%) of a direct travel path.");
     def->sidetext = L("mm or % (zero to disable)");
     def->min = 0;
     def->mode = comExpert;
@@ -259,7 +259,7 @@ void PrintConfigDef::init_fff_params()
     def->label = L("Other layers");
     def->category = OptionCategory::filament;
     def->tooltip = L("Bed temperature for layers after the first one. "
-                   "Set this to zero to disable bed temperature control commands in the output.");
+                   "Set zero to disable bed temperature control commands in the output.");
     def->sidetext = L("°C");
     def->full_label = L("Bed temperature");
     def->sidetext = L("°C");
@@ -627,7 +627,7 @@ void PrintConfigDef::init_fff_params()
     def->label = L("Allow only one skirt loop");
     def->category = OptionCategory::output;
     def->tooltip = L("When using 'Complete individual objects', the default behavior is to draw the skirt around each object."
-        " if you prefer to have only one skirt for the whole plater, use this option.");
+        " if you prefer to have only one skirt for the whole platter, use this option.");
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionBool(false));
 
@@ -756,7 +756,7 @@ void PrintConfigDef::init_fff_params()
     def = this->add("duplicate_distance", coFloat);
     def->label = L("Default distance between objects");
     def->category = OptionCategory::output;
-    def->tooltip = L("Default distance used for the auto-arrange feature of the plater.\nSet to 0 to use the last value instead.");
+    def->tooltip = L("Default distance used for the auto-arrange feature of the platter.\nSet to 0 to use the last value instead.");
     def->sidetext = L("mm");
     def->aliases = { "multiply_distance" };
     def->min = 0;
@@ -1215,7 +1215,7 @@ void PrintConfigDef::init_fff_params()
     def->tooltip = L("Set this to the clearance radius around your extruder. "
                    "If the extruder is not centered, choose the largest value for safety. "
                    "This setting is used to check for collisions and to display the graphical preview "
-                   "in the plater."
+                   "in the platter."
                    "\nSet zero to disable clearance checking.");
     def->sidetext = L("mm");
     def->min = 0;
@@ -1329,7 +1329,7 @@ void PrintConfigDef::init_fff_params()
     def->precision = 6;
     def->can_phony = true;
     def->mode = comAdvanced;
-    def->set_default_value(new ConfigOptionFloatOrPercent(100, true, false));
+    def->set_default_value(new ConfigOptionFloatOrPercent(0, false, false));
 
     def = this->add("fan_always_on", coBools);
     def->label = L("Keep fan always on");
@@ -1399,7 +1399,7 @@ void PrintConfigDef::init_fff_params()
     def->category = OptionCategory::filament;
     def->tooltip = L("Maximum speed allowed for this filament. Limits the maximum "
         "speed of a print to the minimum of the print speed and the filament speed. "
-        "Set to zero for no limit.");
+        "Set zero for no limit.");
     def->sidetext = L("mm/s");
     def->min = 0;
     def->mode = comAdvanced;
@@ -1411,7 +1411,7 @@ void PrintConfigDef::init_fff_params()
     def->category = OptionCategory::filament;
     def->tooltip = L("Maximum volumetric speed allowed for this filament. Limits the maximum volumetric "
         "speed of a print to the minimum of print and filament volumetric speed. "
-        "Set to zero for no limit.");
+        "Set zero for no limit.");
     def->sidetext = L("mm³/s");
     def->min = 0;
     def->mode = comAdvanced;
@@ -1964,7 +1964,7 @@ void PrintConfigDef::init_fff_params()
     def->label = L("First layer");
     def->full_label = L("First layer bed temperature");
     def->category = OptionCategory::filament;
-    def->tooltip = L("Heated build plate temperature for the first layer. Set this to zero to disable "
+    def->tooltip = L("Heated build plate temperature for the first layer. Set zero to disable "
                    "bed temperature control commands in the output.");
     def->sidetext = L("°C");
     def->max = 0;
@@ -2064,7 +2064,7 @@ void PrintConfigDef::init_fff_params()
     def->full_label = L("First layer nozzle temperature");
     def->category = OptionCategory::filament;
     def->tooltip = L("Extruder nozzle temperature for first layer. If you want to control temperature manually "
-                   "during print, set this to zero to disable temperature control commands in the output file.");
+                   "during print, set zero to disable temperature control commands in the output file.");
     def->sidetext = L("°C");
     def->min = 0;
     def->max = max_temp;
@@ -2917,7 +2917,10 @@ void PrintConfigDef::init_fff_params()
     def = this->add("max_speed_reduction", coPercents);
     def->label = L("Max speed reduction");
     def->category = OptionCategory::speed;
-    def->tooltip = L("Set to 90% if you don't want the speed to be reduced by more than 90%.");
+    def->tooltip = L("This setting control by how much the speed can be reduced to increase the layer time."
+        " It's a maximum reduction, so a lower value makes the minimum speed higher."
+        " Set to 90% if you don't want the speed to go below 10% of the current speed."
+        "\nSet zero to disable");
     def->sidetext = L("%");
     def->min = 0;
     def->max = 100;
@@ -3580,7 +3583,7 @@ void PrintConfigDef::init_fff_params()
     def->full_label = L("Enforce lift on first layer");
     def->category = OptionCategory::extruders;
     def->tooltip = L("Select this option to enforce z-lift on the first layer."
-        "\nIf this is enabled and the lift value is 0 or deactivated, then every first move before each object will be lifted by the first layer height.");
+        "\nUseful to still use the lift on the first layer even if the 'Only lift Z below' (retract_lift_above) is higher than 0.");
     def->mode = comAdvanced;
     def->is_vector_extruder = true;
     def->set_default_value(new ConfigOptionBools{ false });
@@ -3726,7 +3729,7 @@ void PrintConfigDef::init_fff_params()
     def = this->add("skirt_distance", coFloat);
     def->label = L("Distance from object");
     def->category = OptionCategory::skirtBrim;
-    def->tooltip = L("Distance between skirt and object(s). Set this to zero to attach the skirt "
+    def->tooltip = L("Distance between skirt and object(s). Set zero to attach the skirt "
                    "to the object(s) and get a brim for better adhesion.");
     def->sidetext = L("mm");
     def->min = 0;
@@ -3763,14 +3766,14 @@ void PrintConfigDef::init_fff_params()
     def->max_literal = { 10, true };
     def->precision = 6;
     def->mode = comAdvanced;
-    def->set_default_value(new ConfigOptionFloatOrPercent(0, false));
+    def->set_default_value(new ConfigOptionFloatOrPercent(130, true));
 
     def = this->add("skirts", coInt);
     def->label = L("Loops (minimum)");
     def->full_label = L("Skirt Loops");
     def->category = OptionCategory::skirtBrim;
     def->tooltip = L("Number of loops for the skirt. If the Minimum Extrusion Length option is set, "
-                   "the number of loops might be greater than the one configured here. Set this to zero "
+                   "the number of loops might be greater than the one configured here. Set zero "
                    "to disable skirt completely.");
     def->min = 0;
     def->mode = comSimple;
@@ -4135,14 +4138,16 @@ void PrintConfigDef::init_fff_params()
     def->sidetext = L("perimeters");
     def->sidetext_width = 20;
     def->category = OptionCategory::perimeter;
-    def->tooltip = L("When you have a medium/hight number of top/bottom solid layers, and a low/medium of perimeters,"
-        " then it have to put some solid infill inside the part to have enough solid layers."
-        "\nBy setting this to something higher than 0, you can remove this 'inside filling'."
-        " This number allow to keep some if there is a low number of perimeter over the void."
-        "\nIf this setting is equal or higher than the top/bottom solid layer count, it won't evict anything."
-        "\nIf this setting is set to 1, it will evict all solid fill are are only over perimeters."
+    def->tooltip = L("In sloping areas, when you have a number of top / bottom solid layers and few perimeters, "
+        " it may be necessary to put some solid infill above/below the perimeters to fulfill the top/bottom layers criteria."
+        "\nBy setting this to something higher than 0, you can control this behaviour, which might be desirable if "
+        "\nundesirable solid infill is being generated on slopes."
+        "\nThe number set here indicates the number of layers between the inside of the part and the air"
+        " at and beyond which solid infill should no longer be added above/below. If this setting is equal or higher than "
+        " the top/bottom solid layer count, it won't do anything. If this setting is set to 1, it will evict "
+        " all solid fill above/below perimeters. "
         "\nSet zero to disable."
-        "\n!! ensure_vertical_shell_thickness may be erased by this setting !! You may want to deactivate at least one of the two.");
+        "\n!! ensure_vertical_shell_thickness may be erased by this setting !!.");
     def->min = 0;
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionInt(2));
@@ -4426,7 +4431,7 @@ void PrintConfigDef::init_fff_params()
     def->tooltip = L("Support material will not be generated for overhangs whose slope angle "
                    "(90° = vertical) is above the given threshold. In other words, this value "
                    "represent the most horizontal slope (measured from the horizontal plane) "
-                   "that you can print without support material. Set to zero for automatic detection "
+                   "that you can print without support material. Set zero for automatic detection "
                    "(recommended).");
     def->sidetext = L("°");
     def->min = 0;
@@ -4446,7 +4451,7 @@ void PrintConfigDef::init_fff_params()
     def->label = L("Other layers");
     def->full_label = L("Temperature");
     def->category = OptionCategory::filament;
-    def->tooltip = L("Extruder nozzle temperature for layers after the first one. Set this to zero to disable "
+    def->tooltip = L("Extruder nozzle temperature for layers after the first one. Set zero to disable "
                    "temperature control commands in the output G-code.");
     def->sidetext = L("°C");
     def->full_label = L("Nozzle temperature");
@@ -4773,6 +4778,14 @@ void PrintConfigDef::init_fff_params()
     def->is_vector_extruder = true;
     def->set_default_value(new ConfigOptionBools{ false });
 
+    def = this->add("wipe_only_crossing", coBools);
+    def->label = L("Wipe only when crossing perimeters");
+    def->category = OptionCategory::extruders;
+    def->tooltip = L("Don't wipe when you don't cross a perimeter.");
+    def->mode = comAdvanced;
+    def->is_vector_extruder = true;
+    def->set_default_value(new ConfigOptionBools{ true });
+
     def = this->add("wipe_speed", coFloats);
     def->label = L("Wipe speed");
     def->category = OptionCategory::extruders;
@@ -5021,7 +5034,7 @@ void PrintConfigDef::init_fff_params()
     def = this->add("z_step", coFloat);
     def->label = L("Z full step");
     def->tooltip = L("Set this to the height moved when your Z motor (or equivalent) turns one step."
-                    "If your motor needs 200 steps to move your head/plater by 1mm, this field should be 1/200 = 0.005."
+                    "If your motor needs 200 steps to move your head/platter by 1mm, this field should be 1/200 = 0.005."
                     "\nNote that the gcode will write the z values with 6 digits after the dot if z_step is set (it's 3 digits if it's disabled)."
                     "\nSet zero to disable.");
     def->cli = "z-step=f";
@@ -5047,7 +5060,7 @@ void PrintConfigDef::init_fff_params()
         "retract_length", "retract_lift", "retract_lift_above", "retract_lift_below", "retract_speed", "deretract_speed", "retract_restart_extra", "retract_before_travel",
         "wipe_extra_perimeter", "wipe_speed",
         // bools
-        "retract_layer_change", "wipe",
+        "retract_layer_change", "wipe", "wipe_only_crossing",
         // percents
         "retract_before_wipe",
         // floatsOrPercents
@@ -5100,6 +5113,7 @@ void PrintConfigDef::init_extruder_option_keys()
         "tool_name",
         "wipe",
 		"wipe_extra_perimeter",
+        "wipe_only_crossing",
         "wipe_speed",
     };
 
@@ -5117,6 +5131,7 @@ void PrintConfigDef::init_extruder_option_keys()
         "seam_gap",
         "wipe",
         "wipe_extra_perimeter",
+        "wipe_only_crossing",
         "wipe_speed",
     };
     assert(std::is_sorted(m_extruder_retract_keys.begin(), m_extruder_retract_keys.end()));
@@ -5736,7 +5751,7 @@ void PrintConfigDef::init_sla_params()
 
     def = this->add("pad_wall_height", coFloat);
     def->label = L("Pad wall height");
-    def->tooltip = L("Defines the pad cavity depth. Set to zero to disable the cavity. "
+    def->tooltip = L("Defines the pad cavity depth. Set zero to disable the cavity. "
                      "Be careful when enabling this feature, as some resins may "
                      "produce an extreme suction effect inside the cavity, "
                      "which makes peeling the print off the vat foil difficult.");
@@ -6328,6 +6343,7 @@ std::unordered_set<std::string> prusa_export_to_remove_keys = {
 "wipe_advanced_nozzle_melted_volume",
 "wipe_advanced",
 "wipe_extra_perimeter",
+"wipe_only_crossing",
 "wipe_speed",
 "wipe_tower_brim",
 "xy_inner_size_compensation",
@@ -6754,6 +6770,9 @@ std::set<const DynamicPrintConfig*> DynamicPrintConfig::value_changed(const t_co
                 if (width_option) {
                     width_option->set_phony(true);
                     spacing_option->set_phony(false);
+                    if (spacing_value == 0)
+                        width_option->value = 0;
+                    else
                     width_option->value = (spacing_option->percent) ? std::round(100 * flow.width / max_nozzle_diameter) : (std::round(flow.width * 10000) / 10000);
                     width_option->percent = spacing_option->percent;
                     something_changed = true;
@@ -6764,6 +6783,9 @@ std::set<const DynamicPrintConfig*> DynamicPrintConfig::value_changed(const t_co
                 if (width_option) {
                     width_option->set_phony(true);
                     spacing_option->set_phony(false);
+                    if (spacing_value == 0)
+                        width_option->value = 0;
+                    else
                     width_option->value = (spacing_option->percent) ? std::round(100 * flow.width / max_nozzle_diameter) : (std::round(flow.width * 10000) / 10000);
                     width_option->percent = spacing_option->percent;
                     something_changed = true;
@@ -6775,9 +6797,13 @@ std::set<const DynamicPrintConfig*> DynamicPrintConfig::value_changed(const t_co
                 if (width_option && perimeter_overlap_option) {
                     width_option->set_phony(true);
                     spacing_option->set_phony(false);
+                    if(spacing_value == 0)
+                        width_option->value = 0;
+                    else {
                     flow.spacing_ratio = std::min(flow.spacing_ratio, float(perimeter_overlap_option->get_abs_value(1)));
                     flow.width = spacing_option->get_abs_value(max_nozzle_diameter) + layer_height_option->value * (1. - 0.25 * PI) * flow.spacing_ratio;
                     width_option->value = (spacing_option->percent) ? std::round(100 * flow.width / max_nozzle_diameter) : (std::round(flow.width * 10000) / 10000);
+                    }
                     width_option->percent = spacing_option->percent;
                     something_changed = true;
                 }
@@ -6789,9 +6815,13 @@ std::set<const DynamicPrintConfig*> DynamicPrintConfig::value_changed(const t_co
                 if (width_option && external_perimeter_overlap_option) {
                     width_option->set_phony(true);
                     spacing_option->set_phony(false);
+                    if (spacing_value == 0)
+                        width_option->value = 0;
+                    else {
                     flow.spacing_ratio = std::min(flow.spacing_ratio * 0.5f, float(external_perimeter_overlap_option->get_abs_value(0.25) + perimeter_overlap_option->get_abs_value(0.25)));
                     flow.width = spacing_option->get_abs_value(max_nozzle_diameter) + layer_height_option->value * (1. - 0.25 * PI) * flow.spacing_ratio;
                     width_option->value = (spacing_option->percent) ? std::round(100 * flow.width / max_nozzle_diameter) : (std::round(flow.width * 10000) / 10000);
+                    }
                     width_option->percent = spacing_option->percent;
                     something_changed = true;
                 }
@@ -6801,6 +6831,9 @@ std::set<const DynamicPrintConfig*> DynamicPrintConfig::value_changed(const t_co
                 if (width_option) {
                     width_option->set_phony(true);
                     spacing_option->set_phony(false);
+                    if (spacing_value == 0)
+                        width_option->value = 0;
+                    else
                     width_option->value = (spacing_option->percent) ? std::round(100 * flow.width / max_nozzle_diameter) : (std::round(flow.width * 10000) / 10000);
                     width_option->percent = spacing_option->percent;
                     something_changed = true;
@@ -6811,6 +6844,9 @@ std::set<const DynamicPrintConfig*> DynamicPrintConfig::value_changed(const t_co
                 if (width_option) {
                     width_option->set_phony(true);
                     spacing_option->set_phony(false);
+                    if (spacing_value == 0)
+                        width_option->value = 0;
+                    else
                     width_option->value = (spacing_option->percent) ? std::round(100 * flow.width / max_nozzle_diameter) : (std::round(flow.width * 10000) / 10000);
                     width_option->percent = spacing_option->percent;
                     something_changed = true;
@@ -6821,6 +6857,9 @@ std::set<const DynamicPrintConfig*> DynamicPrintConfig::value_changed(const t_co
                 if (width_option) {
                     width_option->set_phony(true);
                     spacing_option->set_phony(false);
+                    if (spacing_value == 0)
+                        width_option->value = 0;
+                    else
                     width_option->value = (spacing_option->percent) ? std::round(100 * flow.width / max_nozzle_diameter) : (std::round(flow.width * 10000) / 10000);
                     width_option->percent = spacing_option->percent;
                     something_changed = true;
diff --git a/src/libslic3r/PrintConfig.hpp b/src/libslic3r/PrintConfig.hpp
index ce949a135..faa733bae 100644
--- a/src/libslic3r/PrintConfig.hpp
+++ b/src/libslic3r/PrintConfig.hpp
@@ -1183,6 +1183,7 @@ public:
     ConfigOptionFloat               wipe_advanced_multiplier;
     ConfigOptionFloats              wipe_extra_perimeter;
     ConfigOptionEnum<WipeAlgo>      wipe_advanced_algo;
+    ConfigOptionBools               wipe_only_crossing;
     ConfigOptionFloats              wipe_speed;
     ConfigOptionFloat               z_step;
     ConfigOptionString              color_change_gcode;
@@ -1300,6 +1301,7 @@ protected:
         OPT_PTR(wipe_advanced_multiplier);
         OPT_PTR(wipe_advanced_algo);
         OPT_PTR(wipe_extra_perimeter);
+        OPT_PTR(wipe_only_crossing);
         OPT_PTR(wipe_speed);
         OPT_PTR(z_step);
         OPT_PTR(color_change_gcode);
diff --git a/src/libslic3r/PrintObject.cpp b/src/libslic3r/PrintObject.cpp
index 8e8a725dc..9aff46af9 100644
--- a/src/libslic3r/PrintObject.cpp
+++ b/src/libslic3r/PrintObject.cpp
@@ -14,12 +14,12 @@
 #include "Fill/FillAdaptive.hpp"
 #include "Format/STL.hpp"
 
+#include <atomic>
 #include <utility>
 #include <boost/log/trivial.hpp>
 #include <float.h>
 
 #include <tbb/parallel_for.h>
-#include <tbb/atomic.h>
 
 #include <Shiny/Shiny.h>
 
diff --git a/src/libslic3r/libslic3r.h b/src/libslic3r/libslic3r.h
index 3b4f34264..d1c816bcb 100644
--- a/src/libslic3r/libslic3r.h
+++ b/src/libslic3r/libslic3r.h
@@ -34,32 +34,27 @@ using coord_t = int64_t;
 
 using coordf_t = double;
 
-//FIXME This epsilon value is used for many non-related purposes:
-// For a threshold of a squared Euclidean distance,
-// for a trheshold in a difference of radians,
-// for a threshold of a cross product of two non-normalized vectors etc.
-static constexpr double EPSILON = 1e-4;
 // Scaling factor for a conversion from coord_t to coordf_t: 10e-6
 // This scaling generates a following fixed point representation with for a 32bit integer:
 // 0..4294mm with 1nm resolution
 // int32_t fits an interval of (-2147.48mm, +2147.48mm)
 // with int64_t we don't have to worry anymore about the size of the int.
 static constexpr double SCALING_FACTOR = 0.000001;
-#ifdef __linux__
-static constexpr double UNSCALING_FACTOR = 1000000;
-#else
-static constexpr double UNSCALING_FACTOR = 1 / SCALING_FACTOR;
-#endif
+static constexpr double UNSCALING_FACTOR = 1000000; // 1 / SCALING_FACTOR;
+
+//FIXME This epsilon value is used for many non-related purposes:
+// For a threshold of a squared Euclidean distance,
+// for a trheshold in a difference of radians,
+// for a threshold of a cross product of two non-normalized vectors etc.
+static constexpr double EPSILON = 1e-4;
+static constexpr coord_t SCALED_EPSILON = 100; // coord_t(EPSILON/ SCALING_FACTOR);
 // RESOLUTION, SCALED_RESOLUTION: Used as an error threshold for a Douglas-Peucker polyline simplification algorithm.
 //#define RESOLUTION 0.0125
 //#define SCALED_RESOLUTION 12500
 //#define SCALED_RESOLUTION (RESOLUTION / SCALING_FACTOR)
 static constexpr coordf_t RESOLUTION = 0.0125;
-#ifdef __linux__
-static constexpr coord_t SCALED_RESOLUTION = 12500;
-#else
-static constexpr coord_t SCALED_RESOLUTION = coord_t(0.0125 * UNSCALING_FACTOR);
-#endif
+static constexpr coord_t SCALED_RESOLUTION = 12500; // coord_t(0.0125 * UNSCALING_FACTOR);
+
 //for creating circles (for brim_ear)
 #define POLY_SIDES 24
 #define PI 3.141592653589793238
@@ -72,7 +67,6 @@ static constexpr double INSET_OVERLAP_TOLERANCE = 0.4;
 //inline coord_t scale_(coordf_t v) { return coord_t(floor(v / SCALING_FACTOR + 0.5f)); }
 #define scale_(val) (coord_t)((val) / SCALING_FACTOR)
 
-#define SCALED_EPSILON scale_(EPSILON)
 
 #define SLIC3R_DEBUG_OUT_PATH_PREFIX "out/"
 
diff --git a/src/slic3r/GUI/3DBed.cpp b/src/slic3r/GUI/3DBed.cpp
index 54ddeac97..b5e29302d 100644
--- a/src/slic3r/GUI/3DBed.cpp
+++ b/src/slic3r/GUI/3DBed.cpp
@@ -16,7 +16,11 @@
 
 #include <boost/algorithm/string/predicate.hpp>
 #include <boost/filesystem/operations.hpp>
+#include <boost/locale/generator.hpp>
 #include <boost/log/trivial.hpp>
+#include <boost/nowide/fstream.hpp>
+#include <boost/property_tree/ini_parser.hpp>
+#include <boost/property_tree/ptree.hpp>
 
 static const float GROUND_Z = -0.02f;
 
diff --git a/src/slic3r/GUI/CalibrationAbstractDialog.cpp b/src/slic3r/GUI/CalibrationAbstractDialog.cpp
index 6fa3c1a6b..385d5e0cf 100644
--- a/src/slic3r/GUI/CalibrationAbstractDialog.cpp
+++ b/src/slic3r/GUI/CalibrationAbstractDialog.cpp
@@ -5,10 +5,14 @@
 #include "GUI.hpp"
 #include "GUI_ObjectList.hpp"
 #include "Tab.hpp"
+
 #include <wx/scrolwin.h>
 #include <wx/display.h>
 #include <wx/file.h>
 
+#include <boost/filesystem.hpp>
+#include <boost/filesystem/path.hpp>
+
 #if ENABLE_SCROLLABLE
 static wxSize get_screen_size(wxWindow* window)
 {
diff --git a/src/slic3r/GUI/ConfigManipulation.cpp b/src/slic3r/GUI/ConfigManipulation.cpp
index dd90cea9f..2dabd7dc4 100644
--- a/src/slic3r/GUI/ConfigManipulation.cpp
+++ b/src/slic3r/GUI/ConfigManipulation.cpp
@@ -319,7 +319,7 @@ void ConfigManipulation::toggle_print_fff_options(DynamicPrintConfig* config)
 {
     bool have_perimeters = config->opt_int("perimeters") > 0;
     for (auto el : { "ensure_vertical_shell_thickness", "external_perimeter_speed", "extra_perimeters", "extra_perimeters_overhangs", "extra_perimeters_odd_layers",
-        "external_perimeters_first", "external_perimeters_vase", "external_perimeter_extrusion_width",
+        "external_perimeters_first", "external_perimeters_vase", "external_perimeter_extrusion_width", "external_perimeter_extrusion_spacing",
         "no_perimeter_unsupported_algo", "only_one_perimeter_top", "overhangs", "overhangs_reverse",
         "perimeter_loop", "perimeter_loop_seam","perimeter_speed",
         "seam_position", "small_perimeter_speed", "small_perimeter_min_length", " small_perimeter_max_length", "spiral_vase",
@@ -375,12 +375,12 @@ void ConfigManipulation::toggle_print_fff_options(DynamicPrintConfig* config)
     bool has_solid_infill 		 = has_top_solid_infill || has_bottom_solid_infill || (have_infill && (config->opt_int("solid_infill_every_layers") > 0 || config->opt_float("solid_infill_below_area") > 0));
     // solid_infill_extruder uses the same logic as in Print::extruders()
     for (auto el : { "top_fill_pattern", "bottom_fill_pattern", "solid_fill_pattern", "enforce_full_fill_volume", "external_infill_margin", "bridged_infill_margin",
-        "solid_infill_extruder", "solid_infill_extrusion_width", "solid_infill_speed" })
+        "solid_infill_extruder", "solid_infill_extrusion_width", "solid_infill_extrusion_spacing", "solid_infill_speed" })
         toggle_field(el, has_solid_infill);
 
     toggle_field("infill_first", (has_solid_infill || have_infill));
 
-    for (auto el : { "fill_angle", "fill_angle_increment", "bridge_angle", "infill_extrusion_width",
+    for (auto el : { "fill_angle", "fill_angle_increment", "bridge_angle", "infill_extrusion_width", "infill_extrusion_spacing",
                     "infill_speed" })
         toggle_field(el, have_infill || has_solid_infill);
 
@@ -396,7 +396,7 @@ void ConfigManipulation::toggle_print_fff_options(DynamicPrintConfig* config)
     for (auto el : {"fill_smooth_width, fill_smooth_distribution" })
         toggle_field(el, has_ironing_pattern);
 
-    for (auto el : { "ironing", "top_fill_pattern", "infill_connection_top",  "top_infill_extrusion_width", "top_solid_infill_speed" })
+    for (auto el : { "ironing", "top_fill_pattern", "infill_connection_top",  "top_infill_extrusion_width",  "top_infill_extrusion_spacing", "top_solid_infill_speed" })
         toggle_field(el, has_top_solid_infill);
 
     for (auto el : { "bottom_fill_pattern", "infill_connection_bottom" })
@@ -445,13 +445,27 @@ void ConfigManipulation::toggle_print_fff_options(DynamicPrintConfig* config)
         toggle_field(el, have_support_material && have_support_interface);
     toggle_field("support_material_synchronize_layers", have_support_soluble);
 
-    toggle_field("perimeter_extrusion_width", have_perimeters || have_skirt || have_brim);
+    toggle_field("perimeter_extrusion_width", have_perimeters || have_brim);
+    toggle_field("perimeter_extrusion_spacing", have_perimeters || have_brim);
+    toggle_field("skirt_extrusion_width", have_skirt);
     toggle_field("support_material_extruder", have_support_material || have_skirt);
     toggle_field("support_material_speed", have_support_material || have_brim || have_skirt);
 
+    //for default_extrusion_width/spacing, you need to ahve at least an extrusion_width with 0
+    bool have_default_width = config->option("first_layer_extrusion_width")->getFloat() == 0 ||
+        (config->option("perimeter_extrusion_width")->getFloat() == 0 && (have_perimeters || have_brim)) ||
+        (config->option("external_perimeter_extrusion_width")->getFloat() == 0 && have_perimeters) ||
+        (config->option("infill_extrusion_width")->getFloat() == 0 && (have_infill || has_solid_infill)) ||
+        (config->option("solid_infill_extrusion_width")->getFloat() == 0 && has_solid_infill) ||
+        (config->option("top_infill_extrusion_width")->getFloat() == 0 && has_top_solid_infill) ||
+        (config->option("support_material_extrusion_width")->getFloat() == 0 && have_support_material) ||
+        (config->option("skirt_extrusion_width")->getFloat() == 0 && have_skirt);
+    toggle_field("extrusion_width", have_default_width);
+    toggle_field("extrusion_spacing", have_default_width);
+
     bool has_PP_ironing = has_top_solid_infill && config->opt_bool("ironing");
     for (auto el : { "ironing_type", "ironing_flowrate", "ironing_spacing", "ironing_angle" })
-    	toggle_field(el, has_PP_ironing);
+        toggle_field(el, has_PP_ironing);
 
     bool has_ironing = has_PP_ironing || has_ironing_pattern;
     for (auto el : { "ironing_speed" })
@@ -460,7 +474,7 @@ void ConfigManipulation::toggle_print_fff_options(DynamicPrintConfig* config)
 
     bool have_sequential_printing = config->opt_bool("complete_objects");
     for (auto el : { /*"extruder_clearance_radius", "extruder_clearance_height",*/ "complete_objects_one_skirt",
-		"complete_objects_sort", "complete_objects_one_brim"})
+        "complete_objects_sort", "complete_objects_one_brim"})
         toggle_field(el, have_sequential_printing);
 
     bool have_ooze_prevention = config->opt_bool("ooze_prevention");
diff --git a/src/slic3r/GUI/GUI_App.cpp b/src/slic3r/GUI/GUI_App.cpp
index a6a72e3c9..4bc3360e5 100644
--- a/src/slic3r/GUI/GUI_App.cpp
+++ b/src/slic3r/GUI/GUI_App.cpp
@@ -1908,7 +1908,7 @@ void GUI_App::add_config_menu(wxMenuBar *menu)
                 title += " - " + _L("Language selection");
                 wxMessageDialog dialog(nullptr,
                     _L("Switching the language will trigger application restart.\n"
-                        "You will lose content of the plater.") + "\n\n" +
+                        "You will lose content of the platter.") + "\n\n" +
                     _L("Do you want to proceed?"),
                     title,
                     wxICON_QUESTION | wxOK | wxCANCEL);
diff --git a/src/slic3r/GUI/GUI_ObjectList.cpp b/src/slic3r/GUI/GUI_ObjectList.cpp
index bcc1eef24..3d2280523 100644
--- a/src/slic3r/GUI/GUI_ObjectList.cpp
+++ b/src/slic3r/GUI/GUI_ObjectList.cpp
@@ -15,6 +15,8 @@
 #include "Selection.hpp"
 
 #include <boost/algorithm/string.hpp>
+#include <boost/log/trivial.hpp>
+
 #include "slic3r/Utils/FixModelByWin10.hpp"
 
 #ifdef __WXMSW__
diff --git a/src/slic3r/GUI/KBShortcutsDialog.cpp b/src/slic3r/GUI/KBShortcutsDialog.cpp
index 42a92b8f1..6603bb782 100644
--- a/src/slic3r/GUI/KBShortcutsDialog.cpp
+++ b/src/slic3r/GUI/KBShortcutsDialog.cpp
@@ -66,13 +66,13 @@ void KBShortcutsDialog::fill_shortcuts()
     if (wxGetApp().is_editor()) {
         Shortcuts commands_shortcuts = {
             // File
-            { ctrl + "N", L("New project, clear plater") },
-            { ctrl + "O", L("Open project STL/OBJ/AMF/3MF with config, clear plater") },
+            { ctrl + "N", L("New project, clear platter") },
+            { ctrl + "O", L("Open project STL/OBJ/AMF/3MF with config, clear platter") },
             { ctrl + "S", L("Save project (3mf)") },
             { ctrl + alt + "S", L("Save project as (3mf)") },
             { ctrl + "R", L("(Re)slice") },
             // File>Import
-            { ctrl + "I", L("Import STL/OBJ/AMF/3MF without config, keep plater") },
+            { ctrl + "I", L("Import STL/OBJ/AMF/3MF without config, keep platter") },
             { ctrl + "L", L("Import Config from ini/amf/3mf/gcode") },
             { ctrl + alt + "L", L("Load Config from ini/amf/3mf/gcode and merge") },
             // File>Export
@@ -91,9 +91,9 @@ void KBShortcutsDialog::fill_shortcuts()
             { ctrl + "C", L("Copy to clipboard") },
             { ctrl + "V", L("Paste from clipboard") },
 #ifdef __APPLE__
-            { ctrl + "Shift+" + "R", L("Reload plater from disk") },
+            { ctrl + "Shift+" + "R", L("Reload platter from disk") },
 #else
-            { "F5", L("Reload plater from disk") },
+            { "F5", L("Reload platter from disk") },
 #endif // __APPLE__
             { ctrl + "F", L("Search") },
             // Window
@@ -169,7 +169,7 @@ void KBShortcutsDialog::fill_shortcuts()
 #endif // ENABLE_RENDER_PICKING_PASS
         };
 
-        m_full_shortcuts.push_back({ { _L("Plater"), "" }, plater_shortcuts });
+        m_full_shortcuts.push_back({ { _L("Platter"), "" }, plater_shortcuts });
 
         Shortcuts gizmos_shortcuts = {
             { ctrl, L("All gizmos: Rotate - left mouse button; Pan - right mouse button") },
@@ -187,9 +187,9 @@ void KBShortcutsDialog::fill_shortcuts()
         Shortcuts commands_shortcuts = {
             { ctrl + "O", L("Open a G-code file") },
 #ifdef __APPLE__
-            { ctrl + "Shift+" + "R", L("Reload the plater from disk") },
+            { ctrl + "Shift+" + "R", L("Reload the platter from disk") },
 #else
-            { "F5", L("Reload plater from disk") },
+            { "F5", L("Reload platter from disk") },
 #endif // __APPLE__
         };
 
diff --git a/src/slic3r/GUI/MainFrame.cpp b/src/slic3r/GUI/MainFrame.cpp
index 1804cb13d..c3721a4b9 100644
--- a/src/slic3r/GUI/MainFrame.cpp
+++ b/src/slic3r/GUI/MainFrame.cpp
@@ -428,7 +428,7 @@ void MainFrame::update_layout()
     {
         //layout
         m_plater->Reparent(m_tabpanel);
-        m_tabpanel->InsertPage(0, m_plater, _L("Plater"));
+        m_tabpanel->InsertPage(0, m_plater, _L("Platter"));
         m_main_sizer->Add(m_tabpanel, 1, wxEXPAND);
         update_icon();
         // show
@@ -467,7 +467,7 @@ void MainFrame::update_layout()
         m_tabpanel->Hide();
         m_main_sizer->Add(m_tabpanel, 1, wxEXPAND);
         m_plater_page = new wxPanel(m_tabpanel);
-        m_tabpanel->InsertPage(0, m_plater_page, _L("Plater")); // empty panel just for Plater tab */
+        m_tabpanel->InsertPage(0, m_plater_page, _L("Platter")); // empty panel just for Plater tab */
         update_icon();
         m_plater->Show();
         break;
diff --git a/src/slic3r/GUI/PhysicalPrinterDialog.cpp b/src/slic3r/GUI/PhysicalPrinterDialog.cpp
index 6d54b2d71..91be4c917 100644
--- a/src/slic3r/GUI/PhysicalPrinterDialog.cpp
+++ b/src/slic3r/GUI/PhysicalPrinterDialog.cpp
@@ -5,6 +5,7 @@
 #include <vector>
 #include <string>
 #include <boost/algorithm/string.hpp>
+#include <boost/log/trivial.hpp>
 
 #include <wx/sizer.h>
 #include <wx/stattext.h>
diff --git a/src/slic3r/GUI/Preferences.cpp b/src/slic3r/GUI/Preferences.cpp
index cc44d626a..25941120a 100644
--- a/src/slic3r/GUI/Preferences.cpp
+++ b/src/slic3r/GUI/Preferences.cpp
@@ -4,8 +4,12 @@
 #include "Plater.hpp"
 #include "I18N.hpp"
 #include "libslic3r/AppConfig.hpp"
+
 #include <wx/notebook.h>
 
+#include <boost/filesystem.hpp>
+#include <boost/filesystem/path.hpp>
+
 namespace Slic3r {
 namespace GUI {
 
@@ -134,7 +138,7 @@ void PreferencesDialog::build()
 		def_combobox_auto_switch_preview.gui_flags = "show_value";
 		def_combobox_auto_switch_preview.enum_values.push_back(_u8L("Don't switch"));
 		def_combobox_auto_switch_preview.enum_values.push_back(_u8L("Switch when possible"));
-		def_combobox_auto_switch_preview.enum_values.push_back(_u8L("Only if on plater"));
+		def_combobox_auto_switch_preview.enum_values.push_back(_u8L("Only if on platter"));
 		def_combobox_auto_switch_preview.enum_values.push_back(_u8L("Only when GCode is ready"));
 		if (app_config->get("auto_switch_preview") == "0")
 			def_combobox_auto_switch_preview.set_default_value(new ConfigOptionStrings{ def_combobox_auto_switch_preview.enum_values[0] });
@@ -807,7 +811,7 @@ void PreferencesDialog::create_settings_mode_widget(wxNotebook* tabs)
 #ifndef WIN32
 		+ " " + unstable_warning
 #endif
-		+ "\n* " + _L("Old layout: all windows are in the application, settings are on the top tab bar and the plater choice in on the bottom of the plater view.")
+		+ "\n* " + _L("Old layout: all windows are in the application, settings are on the top tab bar and the platter choice in on the bottom of the platter view.")
 		+ "\n* " + _L("Settings button: all windows are in the application, no tabs: you have to clic on settings gears to switch to settings tabs.")
 		+ "\n* " + _L("Settings window: settings are displayed in their own window. You have to clic on settings gears to show the settings window.")
 	);
diff --git a/src/slic3r/GUI/Search.cpp b/src/slic3r/GUI/Search.cpp
index 6c75eb153..b35efd92c 100644
--- a/src/slic3r/GUI/Search.cpp
+++ b/src/slic3r/GUI/Search.cpp
@@ -1,7 +1,9 @@
 #include "Search.hpp"
 
 #include <cstddef>
+#include <regex>
 #include <string>
+
 #include <boost/algorithm/string.hpp>
 #include <boost/optional.hpp>
 #include <boost/nowide/convert.hpp>
diff --git a/src/slic3r/GUI/Tab.cpp b/src/slic3r/GUI/Tab.cpp
index 7fe2c5c7b..38ec11954 100644
--- a/src/slic3r/GUI/Tab.cpp
+++ b/src/slic3r/GUI/Tab.cpp
@@ -22,6 +22,7 @@
 
 #include <wx/bmpcbox.h>
 #include <wx/bmpbuttn.h>
+#include <wx/collpane.h>
 #include <wx/treectrl.h>
 #include <wx/imaglist.h>
 #include <wx/settings.h>
@@ -29,10 +30,12 @@
 
 #include <boost/algorithm/string/split.hpp>
 #include <boost/algorithm/string/predicate.hpp>
-
-#include <boost/algorithm/string/replace.hpp>#include <boost/algorithm/string/trim.hpp>
+#include <boost/algorithm/string/replace.hpp>
+#include <boost/algorithm/string/trim.hpp>
 #include <boost/filesystem.hpp>
 #include <boost/filesystem/path.hpp>
+#include <boost/lexical_cast.hpp>
+
 #include "wxExtensions.hpp"
 #include "PresetComboBoxes.hpp"
 #include <wx/wupdlock.h>
@@ -2345,6 +2348,7 @@ void TabFilament::add_filament_overrides_page()
                                         "filament_retract_layer_change",
                                         "filament_seam_gap",
                                         "filament_wipe",
+                                        "filament_wipe_extra_perimeter",
                                         "filament_wipe_speed",
                                         "filament_wipe_extra_perimeter"
                                      })
@@ -2374,6 +2378,7 @@ void TabFilament::update_filament_overrides_page()
                                             "filament_retract_layer_change",
                                             "filament_seam_gap",
                                             "filament_wipe",
+                                            "filament_wipe_extra_perimeter",
                                             "filament_wipe_speed",
                                             "filament_wipe_extra_perimeter"
                                         };
@@ -2920,11 +2925,21 @@ void TabPrinter::clear_pages()
 
 void TabPrinter::toggle_options()
 {
-    if (!m_active_page || m_presets->get_edited_preset().printer_technology() == ptSLA)
+    if (!m_active_page || m_presets->get_edited_preset().printer_technology() != ptFFF)
         return;
 
     Field* field;
 
+    const DynamicPrintConfig& print_config = m_preset_bundle->fff_prints.get_edited_preset().config;
+    const DynamicPrintConfig& filament_config = m_preset_bundle->filaments.get_edited_preset().config;
+    const DynamicPrintConfig& printer_config = m_preset_bundle->printers.get_edited_preset().config;
+
+    // Print config values
+    DynamicPrintConfig full_print_config;
+    full_print_config.apply(print_config);
+    full_print_config.apply(filament_config);
+    full_print_config.apply(printer_config);
+
     bool have_multiple_extruders = m_extruders_count > 1;
     field = get_field("toolchange_gcode");
     if (field) field->toggle(have_multiple_extruders);
@@ -3001,7 +3016,7 @@ void TabPrinter::toggle_options()
 
         // some options only apply when not using firmware retraction
         vec.resize(0);
-        vec = { "retract_speed", "deretract_speed", "retract_before_wipe", "retract_restart_extra", "wipe", "wipe_speed" };
+        vec = { "retract_speed", "deretract_speed", "retract_before_wipe", "retract_restart_extra", "wipe", "wipe_speed" , "wipe_only_crossing"};
         for (auto el : vec) {
             field = get_field(el, i);
             if (field)
@@ -3009,13 +3024,17 @@ void TabPrinter::toggle_options()
         }
 
         bool wipe = m_config->opt_bool("wipe", i) && have_retract_length;
-        vec = { "retract_before_wipe", "wipe_speed" };
+        vec = { "retract_before_wipe", "wipe_only_crossing", "wipe_speed" };
         for (auto el : vec) {
             field = get_field(el, i);
             if (field)
                 field->toggle(wipe);
         }
 
+        // wipe_only_crossing can only work if avoid_crossing_perimeters
+        if (!full_print_config.opt_bool("avoid_crossing_perimeters"))
+            get_field("wipe_only_crossing", i)->toggle(false);
+
         if (use_firmware_retraction && wipe) {
             wxMessageDialog dialog(parent(),
                 _(L("The Wipe option is not available when using the Firmware Retraction mode.\n"
diff --git a/src/slic3r/Utils/PresetUpdater.cpp b/src/slic3r/Utils/PresetUpdater.cpp
index bf952bb8c..37821d7c8 100644
--- a/src/slic3r/Utils/PresetUpdater.cpp
+++ b/src/slic3r/Utils/PresetUpdater.cpp
@@ -6,12 +6,15 @@
 #include <ostream>
 #include <utility>
 #include <stdexcept>
-#include <boost/format.hpp>
+
 #include <boost/algorithm/string.hpp>
 #include <boost/filesystem.hpp>
 #include <boost/filesystem/fstream.hpp>
+#include <boost/format.hpp>
 #include <boost/lexical_cast.hpp>
 #include <boost/log/trivial.hpp>
+#include <boost/property_tree/json_parser.hpp>
+#include <boost/property_tree/ptree.hpp> 
 
 #include <wx/app.h>
 #include <wx/msgdlg.h>