GLVolume: split composite_id to object_id, volume_id and instance_id.

WIP: Added creation of GLVolumes for SLA supports.

9 files changed, 302 insertions, 106 deletions

diff --git a/src/slic3r/GUI/3DScene.cpp b/src/slic3r/GUI/3DScene.cpp
index 565ef94fb..e381cb854 100644
--- a/src/slic3r/GUI/3DScene.cpp
+++ b/src/slic3r/GUI/3DScene.cpp
@@ -2,13 +2,14 @@
 
 #include "3DScene.hpp"
 
-#include "../../libslic3r/ExtrusionEntity.hpp"
-#include "../../libslic3r/ExtrusionEntityCollection.hpp"
-#include "../../libslic3r/Geometry.hpp"
-#include "../../libslic3r/GCode/PreviewData.hpp"
-#include "../../libslic3r/Print.hpp"
-#include "../../libslic3r/Slicing.hpp"
-#include "../../slic3r/GUI/PresetBundle.hpp"
+#include "libslic3r/ExtrusionEntity.hpp"
+#include "libslic3r/ExtrusionEntityCollection.hpp"
+#include "libslic3r/Geometry.hpp"
+#include "libslic3r/GCode/PreviewData.hpp"
+#include "libslic3r/Print.hpp"
+#include "libslic3r/SLAPrint.hpp"
+#include "libslic3r/Slicing.hpp"
+#include "slic3r/GUI/PresetBundle.hpp"
 #include "GCode/Analyzer.hpp"
 
 #include <stdio.h>
@@ -209,7 +210,9 @@ GLVolume::GLVolume(float r, float g, float b, float a)
 #endif // ENABLE_MODELVOLUME_TRANSFORM
     , m_transformed_convex_hull_bounding_box_dirty(true)
     , m_convex_hull(nullptr)
-    , composite_id(-1)
+    , object_id(-1)
+    , volume_id(-1)
+    , instance_id(-1)
     , extruder_id(0)
     , selected(false)
     , disabled(false)
@@ -755,7 +758,9 @@ std::vector<int> GLVolumeCollection::load_object(
             // finalize_geometry() clears the vertex arrays, therefore the bounding box has to be computed before finalize_geometry().
             v.bounding_box = v.indexed_vertex_array.bounding_box();
             v.indexed_vertex_array.finalize_geometry(use_VBOs);
-            v.composite_id = obj_idx * 1000000 + volume_idx * 1000 + instance_idx;
+            v.object_id    = obj_idx;
+            v.volume_id    = volume_idx;
+            v.instance_id  = instance_idx;
             if (model_volume->is_model_part())
             {
                 v.set_convex_hull(model_volume->get_convex_hull());
@@ -780,6 +785,61 @@ std::vector<int> GLVolumeCollection::load_object(
     return volumes_idx; 
 }
 
+// Load SLA auxiliary GLVolumes (for support trees or pad).
+std::vector<int> GLVolumeCollection::load_object_auxiliary(
+    const ModelObject       *model_object,
+    const SLAPrintObject    *print_object,
+    int                      obj_idx,
+    SLAPrintObjectStep       milestone,
+    bool                     use_VBOs)
+{
+    std::vector<int> volumes_idx;
+    // Find the SLAPrintObject's instance to it.
+    if (print_object->is_step_done(milestone)) {
+        // Get the support mesh.
+        TriangleMesh mesh;
+        switch (milestone) {
+        case slaposSupportTree: mesh = print_object->support_mesh(); break;
+        case slaposBasePool:    mesh = print_object->pad_mesh();     break;
+        default:
+            assert(false);
+        }
+		// Convex hull is required for out of print bed detection.
+		TriangleMesh convex_hull = mesh.convex_hull_3d();
+        const std::vector<SLAPrintObject::Instance> &instances = print_object->instances();
+        std::map<ModelID, int> map_instances;
+        for (int i = 0; i < (int)model_object->instances.size(); ++ i)
+            map_instances[model_object->instances[i]->id()] = i;
+        for (const SLAPrintObject::Instance &instance : instances) {
+            auto model_instance_it = map_instances.find(instance.instance_id);
+            assert(model_instance_it != map_instances.end());
+            const int instance_idx = model_instance_it->second;
+            const ModelInstance *model_instance = model_object->instances[instance_idx];
+            volumes_idx.push_back(int(this->volumes.size()));
+            float color[4] { 0.f, 0.f, 1.f, 1.f };
+            this->volumes.emplace_back(new GLVolume(color));
+            GLVolume &v = *this->volumes.back();
+            if (use_VBOs)
+                v.indexed_vertex_array.load_mesh_full_shading(mesh);
+            else
+                v.indexed_vertex_array.load_mesh_flat_shading(mesh);
+            // finalize_geometry() clears the vertex arrays, therefore the bounding box has to be computed before finalize_geometry().
+            v.bounding_box = v.indexed_vertex_array.bounding_box();
+            v.indexed_vertex_array.finalize_geometry(use_VBOs);
+            v.object_id    = obj_idx;
+            v.volume_id    = -1; // SLA supports
+            v.instance_id  = instance_idx;
+			v.set_convex_hull(convex_hull);
+            v.is_modifier  = false;
+            v.shader_outside_printer_detection_enabled = true;
+			v.set_instance_transformation(model_instance->get_transformation());
+			// Leave the volume transformation at identity.
+            // v.set_volume_transformation(model_volume->get_transformation());
+        }
+    }
+
+    return volumes_idx; 
+}
 
 int GLVolumeCollection::load_wipe_tower_preview(
     int obj_idx, float pos_x, float pos_y, float width, float depth, float height, float rotation_angle, bool use_VBOs, bool size_unknown, float brim_width)
@@ -851,7 +911,9 @@ int GLVolumeCollection::load_wipe_tower_preview(
     // finalize_geometry() clears the vertex arrays, therefore the bounding box has to be computed before finalize_geometry().
     v.bounding_box = v.indexed_vertex_array.bounding_box();
     v.indexed_vertex_array.finalize_geometry(use_VBOs);
-    v.composite_id = obj_idx * 1000000;
+    v.object_id    = obj_idx;
+    v.volume_id    = 0;
+    v.instance_id  = 0;
     v.is_wipe_tower = true;
     v.shader_outside_printer_detection_enabled = ! size_unknown;
     return int(this->volumes.size() - 1);
@@ -1848,6 +1910,11 @@ void _3DScene::set_print(wxGLCanvas* canvas, Print* print)
     s_canvas_mgr.set_print(canvas, print);
 }
 
+void _3DScene::set_SLA_print(wxGLCanvas* canvas, SLAPrint* print)
+{
+    s_canvas_mgr.set_SLA_print(canvas, print);
+}
+
 void _3DScene::set_model(wxGLCanvas* canvas, Model* model)
 {
     s_canvas_mgr.set_model(canvas, model);
diff --git a/src/slic3r/GUI/3DScene.hpp b/src/slic3r/GUI/3DScene.hpp
index 87c9df385..e611e7f54 100644
--- a/src/slic3r/GUI/3DScene.hpp
+++ b/src/slic3r/GUI/3DScene.hpp
@@ -1,13 +1,13 @@
 #ifndef slic3r_3DScene_hpp_
 #define slic3r_3DScene_hpp_
 
-#include "../../libslic3r/libslic3r.h"
-#include "../../libslic3r/Point.hpp"
-#include "../../libslic3r/Line.hpp"
-#include "../../libslic3r/TriangleMesh.hpp"
-#include "../../libslic3r/Utils.hpp"
-#include "../../libslic3r/Model.hpp"
-#include "../../slic3r/GUI/GLCanvas3DManager.hpp"
+#include "libslic3r/libslic3r.h"
+#include "libslic3r/Point.hpp"
+#include "libslic3r/Line.hpp"
+#include "libslic3r/TriangleMesh.hpp"
+#include "libslic3r/Utils.hpp"
+#include "libslic3r/Model.hpp"
+#include "slic3r/GUI/GLCanvas3DManager.hpp"
 
 class wxBitmap;
 class wxWindow;
@@ -16,6 +16,9 @@ namespace Slic3r {
 
 class Print;
 class PrintObject;
+class SLAPrint;
+class SLAPrintObject;
+enum  SLAPrintObjectStep;
 class Model;
 class ModelObject;
 class GCodePreviewData;
@@ -290,8 +293,15 @@ public:
     float               color[4];
     // Color used to render this volume.
     float               render_color[4];
-    // An ID containing the object ID, volume ID and instance ID.
-    int                 composite_id;
+    // Object ID, which is equal to the index of the respective ModelObject in Model.objects array.
+    int                 object_id;
+    // Volume ID, which is equal to the index of the respective ModelVolume in ModelObject.volumes array.
+    // If negative, it is an index of a geometry produced by the PrintObject for the respective ModelObject,
+    // and which has no associated ModelVolume in ModelObject.volumes. For example, SLA supports.
+    // Volume with a negative volume_id cannot be picked independently, it will pick the associated instance.
+    int                 volume_id;
+    // Instance ID, which is equal to the index of the respective ModelInstance in ModelObject.instances array.
+    int                 instance_id;
     // An ID containing the extruder ID (used to select color).
     int                 extruder_id;
     // Is this object selected?
@@ -404,9 +414,9 @@ public:
 
     void set_convex_hull(const TriangleMesh& convex_hull);
 
-    int                 object_idx() const { return this->composite_id / 1000000; }
-    int                 volume_idx() const { return (this->composite_id / 1000) % 1000; }
-    int                 instance_idx() const { return this->composite_id % 1000; }
+    int                 object_idx() const { return this->object_id; }
+    int                 volume_idx() const { return this->volume_id; }
+    int                 instance_idx() const { return this->instance_id; }
 
 #if ENABLE_MODELVOLUME_TRANSFORM
     Transform3d world_matrix() const { return m_instance_transformation.get_matrix() * m_volume_transformation.get_matrix(); }
@@ -489,6 +499,14 @@ public:
         const std::string       &color_by,
         bool                     use_VBOs);
 
+    // Load SLA auxiliary GLVolumes (for support trees or pad).
+    std::vector<int> load_object_auxiliary(
+        const ModelObject       *model_object,
+        const SLAPrintObject    *print_object,
+        int                      obj_idx,
+        SLAPrintObjectStep       milestone,
+        bool                     use_VBOs);
+
     int load_wipe_tower_preview(
         int obj_idx, float pos_x, float pos_y, float width, float depth, float height, float rotation_angle, bool use_VBOs, bool size_unknown, float brim_width);
 
@@ -556,6 +574,7 @@ public:
 
     static void set_config(wxGLCanvas* canvas, DynamicPrintConfig* config);
     static void set_print(wxGLCanvas* canvas, Print* print);
+    static void set_SLA_print(wxGLCanvas* canvas, SLAPrint* print);
     static void set_model(wxGLCanvas* canvas, Model* model);
 
     static void set_bed_shape(wxGLCanvas* canvas, const Pointfs& shape);
diff --git a/src/slic3r/GUI/BackgroundSlicingProcess.cpp b/src/slic3r/GUI/BackgroundSlicingProcess.cpp
index d9a60caa9..d6bb01c87 100644
--- a/src/slic3r/GUI/BackgroundSlicingProcess.cpp
+++ b/src/slic3r/GUI/BackgroundSlicingProcess.cpp
@@ -235,6 +235,12 @@ void BackgroundSlicingProcess::stop_internal()
 	m_print->set_cancel_callback([](){});
 }
 
+bool BackgroundSlicingProcess::empty() const
+{
+	assert(m_print != nullptr);
+	return m_print->empty();
+}
+
 std::string BackgroundSlicingProcess::validate()
 {
 	assert(m_print != nullptr);
diff --git a/src/slic3r/GUI/BackgroundSlicingProcess.hpp b/src/slic3r/GUI/BackgroundSlicingProcess.hpp
index b008437c0..da3eb776e 100644
--- a/src/slic3r/GUI/BackgroundSlicingProcess.hpp
+++ b/src/slic3r/GUI/BackgroundSlicingProcess.hpp
@@ -51,11 +51,15 @@ public:
 	// Useful when the Model or configuration is being changed drastically.
 	bool reset();
 
-	// Validate the print. Returns an empty string if valid, returns an error message if invalid.
-	std::string validate();
 	// Apply config over the print. Returns false, if the new config values caused any of the already
 	// processed steps to be invalidated, therefore the task will need to be restarted.
 	Print::ApplyStatus apply(const Model &model, const DynamicPrintConfig &config);
+	// After calling apply, the empty() call will report whether there is anything to slice.
+	bool 		empty() const;
+	// Validate the print. Returns an empty string if valid, returns an error message if invalid.
+	// Call validate before calling start().
+	std::string validate();
+
 	// Set the export path of the G-code.
 	// Once the path is set, the G-code 
 	void schedule_export(const std::string &path);
diff --git a/src/slic3r/GUI/GLCanvas3D.cpp b/src/slic3r/GUI/GLCanvas3D.cpp
index 707359f3e..f9daa36d0 100644
--- a/src/slic3r/GUI/GLCanvas3D.cpp
+++ b/src/slic3r/GUI/GLCanvas3D.cpp
@@ -1,16 +1,16 @@
 #include "GLCanvas3D.hpp"
 
-#include "../../admesh/stl.h"
-#include "../../libslic3r/libslic3r.h"
-#include "../../slic3r/GUI/3DScene.hpp"
-#include "../../slic3r/GUI/GLShader.hpp"
-#include "../../slic3r/GUI/GUI.hpp"
-#include "../../slic3r/GUI/PresetBundle.hpp"
-#include "../../slic3r/GUI/GLGizmo.hpp"
-#include "../../libslic3r/ClipperUtils.hpp"
-#include "../../libslic3r/PrintConfig.hpp"
-#include "../../libslic3r/GCode/PreviewData.hpp"
-#include "../../libslic3r/Geometry.hpp"
+#include "admesh/stl.h"
+#include "libslic3r/libslic3r.h"
+#include "slic3r/GUI/3DScene.hpp"
+#include "slic3r/GUI/GLShader.hpp"
+#include "slic3r/GUI/GUI.hpp"
+#include "slic3r/GUI/PresetBundle.hpp"
+#include "slic3r/GUI/GLGizmo.hpp"
+#include "libslic3r/ClipperUtils.hpp"
+#include "libslic3r/PrintConfig.hpp"
+#include "libslic3r/GCode/PreviewData.hpp"
+#include "libslic3r/Geometry.hpp"
 #include "GUI_App.hpp"
 #include "GUI_ObjectList.hpp"
 #include "GUI_ObjectManipulation.hpp"
@@ -25,7 +25,8 @@
 #include <wx/tooltip.h>
 
 // Print now includes tbb, and tbb includes Windows. This breaks compilation of wxWidgets if included before wx.
-#include "../../libslic3r/Print.hpp"
+#include "libslic3r/Print.hpp"
+#include "libslic3r/SLAPrint.hpp"
 
 #include <tbb/parallel_for.h>
 #include <tbb/spin_mutex.h>
@@ -3065,6 +3066,7 @@ GLCanvas3D::GLCanvas3D(wxGLCanvas* canvas)
     , m_toolbar(*this)
     , m_config(nullptr)
     , m_print(nullptr)
+    , m_sla_print(nullptr)
     , m_model(nullptr)
     , m_dirty(true)
     , m_initialized(false)
@@ -3247,7 +3249,11 @@ bool GLCanvas3D::move_volume_up(unsigned int id)
     if ((id > 0) && (id < (unsigned int)m_volumes.volumes.size()))
     {
         std::swap(m_volumes.volumes[id - 1], m_volumes.volumes[id]);
-        std::swap(m_volumes.volumes[id - 1]->composite_id, m_volumes.volumes[id]->composite_id);
+        GLVolume &v1 = *m_volumes.volumes[id - 1];
+        GLVolume &v2 = *m_volumes.volumes[id];
+        std::swap(v1.object_id,   v2.object_id);
+        std::swap(v1.volume_id,   v2.volume_id);
+        std::swap(v1.instance_id, v2.instance_id);
         return true;
     }
 
@@ -3259,7 +3265,11 @@ bool GLCanvas3D::move_volume_down(unsigned int id)
     if ((id >= 0) && (id + 1 < (unsigned int)m_volumes.volumes.size()))
     {
         std::swap(m_volumes.volumes[id + 1], m_volumes.volumes[id]);
-        std::swap(m_volumes.volumes[id + 1]->composite_id, m_volumes.volumes[id]->composite_id);
+        GLVolume &v1 = *m_volumes.volumes[id + 1];
+        GLVolume &v2 = *m_volumes.volumes[id];
+        std::swap(v1.object_id,   v2.object_id);
+        std::swap(v1.volume_id,   v2.volume_id);
+        std::swap(v1.instance_id, v2.instance_id);
         return true;
     }
 
@@ -3276,6 +3286,11 @@ void GLCanvas3D::set_print(Print* print)
     m_print = print;
 }
 
+void GLCanvas3D::set_SLA_print(SLAPrint* print)
+{
+    m_sla_print = print;
+}
+
 void GLCanvas3D::set_model(Model* model)
 {
     m_model = model;
@@ -3631,6 +3646,13 @@ std::vector<int> GLCanvas3D::load_object(const Model& model, int obj_idx)
     return std::vector<int>();
 }
 
+std::vector<int> GLCanvas3D::load_support_meshes(const Model& model, int obj_idx)
+{
+    std::vector<int> volumes = m_volumes.load_object_auxiliary(model.objects[obj_idx], m_sla_print->objects()[obj_idx], obj_idx, slaposSupportTree, m_use_VBOs && m_initialized);
+	append(volumes, m_volumes.load_object_auxiliary(model.objects[obj_idx], m_sla_print->objects()[obj_idx], obj_idx, slaposBasePool, m_use_VBOs && m_initialized));
+    return volumes;
+}
+
 int GLCanvas3D::get_first_volume_id(int obj_idx) const
 {
     for (int i = 0; i < (int)m_volumes.volumes.size(); ++i)
@@ -3682,11 +3704,14 @@ void GLCanvas3D::reload_scene(bool force)
 
     m_reload_delayed = false;
 
+    PrinterTechnology printer_technology = wxGetApp().preset_bundle->printers.get_edited_preset().printer_technology();
     if (m_regenerate_volumes)
     {
         for (unsigned int obj_idx = 0; obj_idx < (unsigned int)m_model->objects.size(); ++obj_idx)
         {
             load_object(*m_model, obj_idx);
+            if (printer_technology == ptSLA)
+                load_support_meshes(*m_model, obj_idx);
         }
     }
 
@@ -3694,7 +3719,8 @@ void GLCanvas3D::reload_scene(bool force)
 
     if (m_regenerate_volumes)
     {
-        if (m_config->has("nozzle_diameter") && wxGetApp().preset_bundle->printers.get_edited_preset().printer_technology() == ptFFF)
+        PrinterTechnology printer_technology = wxGetApp().preset_bundle->printers.get_edited_preset().printer_technology();
+        if (printer_technology == ptFFF && m_config->has("nozzle_diameter"))
         {
             // Should the wipe tower be visualized ?
             unsigned int extruders_count = (unsigned int)dynamic_cast<const ConfigOptionFloats*>(m_config->option("nozzle_diameter"))->values.size();
diff --git a/src/slic3r/GUI/GLCanvas3D.hpp b/src/slic3r/GUI/GLCanvas3D.hpp
index f182f2c37..eb45bddb5 100644
--- a/src/slic3r/GUI/GLCanvas3D.hpp
+++ b/src/slic3r/GUI/GLCanvas3D.hpp
@@ -22,6 +22,7 @@ namespace Slic3r {
 
 class GLShader;
 class ExPolygon;
+class SLAPrint;
 
 namespace GUI {
 
@@ -447,17 +448,25 @@ public:
 
         struct Cache
         {
+            // Cache of GLVolume derived transformation matrices, valid during mouse dragging.
             VolumesCache volumes_data;
+            // Center of the dragged selection, valid during mouse dragging.
             Vec3d dragging_center;
+            // Map from indices of ModelObject instances in Model::objects
+            // to a set of indices of ModelVolume instances in ModelObject::instances
+            // Here the index means a position inside the respective std::vector, not ModelID.
             ObjectIdxsToInstanceIdxsMap content;
         };
 
+        // Volumes owned by GLCanvas3D.
         GLVolumePtrs* m_volumes;
+        // Model, not owned.
         Model* m_model;
 
         bool m_valid;
         EMode m_mode;
         EType m_type;
+        // set of indices to m_volumes
         IndicesList m_list;
         Cache m_cache;
         mutable BoundingBoxf3 m_bounding_box;
@@ -692,6 +701,7 @@ private:
     Selection m_selection;
     DynamicPrintConfig* m_config;
     Print* m_print;
+    SLAPrint* m_sla_print;
     Model* m_model;
 
     bool m_dirty;
@@ -745,6 +755,7 @@ public:
 
     void set_config(DynamicPrintConfig* config);
     void set_print(Print* print);
+    void set_SLA_print(SLAPrint* print);
     void set_model(Model* model);
 
     const Selection& get_selection() const { return m_selection; }
@@ -810,6 +821,9 @@ public:
     std::vector<int> load_object(const ModelObject& model_object, int obj_idx, std::vector<int> instance_idxs);
     std::vector<int> load_object(const Model& model, int obj_idx);
 
+    // Load SLA support tree and SLA pad meshes into the scene, if available at the respective SLAPrintObject instances.
+    std::vector<int> load_support_meshes(const Model& model, int obj_idx);
+
     int get_first_volume_id(int obj_idx) const;
     int get_in_object_volume_id(int scene_vol_idx) const;
 
diff --git a/src/slic3r/GUI/GLCanvas3DManager.cpp b/src/slic3r/GUI/GLCanvas3DManager.cpp
index d8ff798ed..d38b2f193 100644
--- a/src/slic3r/GUI/GLCanvas3DManager.cpp
+++ b/src/slic3r/GUI/GLCanvas3DManager.cpp
@@ -284,6 +284,14 @@ void GLCanvas3DManager::set_print(wxGLCanvas* canvas, Print* print)
         it->second->set_print(print);
 }
 
+
+void GLCanvas3DManager::set_SLA_print(wxGLCanvas* canvas, SLAPrint* print)
+{
+    CanvasesMap::iterator it = _get_canvas(canvas);
+    if (it != m_canvases.end())
+        it->second->set_SLA_print(print);
+}
+
 void GLCanvas3DManager::set_model(wxGLCanvas* canvas, Model* model)
 {
     CanvasesMap::iterator it = _get_canvas(canvas);
diff --git a/src/slic3r/GUI/GLCanvas3DManager.hpp b/src/slic3r/GUI/GLCanvas3DManager.hpp
index 917b4a4e8..232c928f3 100644
--- a/src/slic3r/GUI/GLCanvas3DManager.hpp
+++ b/src/slic3r/GUI/GLCanvas3DManager.hpp
@@ -14,6 +14,7 @@ namespace Slic3r {
 
 class DynamicPrintConfig;
 class Print;
+class SLAPrint;
 class Model;
 class ExPolygon;
 typedef std::vector<ExPolygon> ExPolygons;
@@ -95,6 +96,7 @@ public:
 
     void set_config(wxGLCanvas* canvas, DynamicPrintConfig* config);
     void set_print(wxGLCanvas* canvas, Print* print);
+    void set_SLA_print(wxGLCanvas* canvas, SLAPrint* print);
     void set_model(wxGLCanvas* canvas, Model* model);
 
     void set_bed_shape(wxGLCanvas* canvas, const Pointfs& shape);
diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
index c57ae381f..77b817a3d 100644
--- a/src/slic3r/GUI/Plater.cpp
+++ b/src/slic3r/GUI/Plater.cpp
@@ -447,7 +447,7 @@ struct Sidebar::priv
 
 void Sidebar::priv::show_preset_comboboxes()
 {
-    const bool showSLA = wxGetApp().preset_bundle->printers.get_edited_preset().printer_technology() == ptSLA;
+    const bool showSLA = plater->printer_technology() == ptSLA;
 
     wxWindowUpdateLocker noUpdates_scrolled(scrolled);
 //     scrolled->Freeze();
@@ -630,9 +630,8 @@ void Sidebar::update_presets(Preset::Type preset_type)
 
 	case Preset::TYPE_PRINTER:
 	{
-		PrinterTechnology printer_technology = preset_bundle.printers.get_edited_preset().printer_technology();
 		// Update the print choosers to only contain the compatible presets, update the dirty flags.
-		if (printer_technology == ptFFF)
+		if (p->plater->printer_technology() == ptFFF)
 			preset_bundle.prints.update_platter_ui(p->combo_print);
 		else
 			preset_bundle.sla_materials.update_platter_ui(p->combo_sla_material);
@@ -640,7 +639,7 @@ void Sidebar::update_presets(Preset::Type preset_type)
 		preset_bundle.printers.update_platter_ui(p->combo_printer);
 		// Update the filament choosers to only contain the compatible presets, update the color preview,
 		// update the dirty flags.
-        if (printer_technology == ptFFF) {
+		if (p->plater->printer_technology() == ptFFF) {
             for (size_t i = 0; i < p->combos_filament.size(); ++ i)
                 preset_bundle.update_platter_filament_ui(i, p->combos_filament[i]);
 		}
@@ -785,7 +784,7 @@ void Sidebar::show_buttons(const bool show)
         TabPrinter *tab = dynamic_cast<TabPrinter*>(wxGetApp().tab_panel()->GetPage(i));
         if (!tab)
             continue;
-        if (wxGetApp().preset_bundle->printers.get_selected_preset().printer_technology() == ptFFF) {
+		if (p->plater->printer_technology() == ptFFF) {
             p->btn_send_gcode->Show(show && !tab->m_config->opt_string("print_host").empty());
         }
         break;
@@ -875,10 +874,11 @@ struct Plater::priv
 
     // Data
     Slic3r::DynamicPrintConfig *config;
-    Slic3r::Print print;
-	Slic3r::SLAPrint sla_print;
-    Slic3r::Model model;
-    Slic3r::GCodePreviewData gcode_preview_data;
+    Slic3r::Print               print;
+	Slic3r::SLAPrint            sla_print;
+    Slic3r::Model               model;
+    PrinterTechnology           printer_technology = ptFFF;
+    Slic3r::GCodePreviewData    gcode_preview_data;
 
     // GUI elements
     wxNotebook *notebook;
@@ -921,8 +921,21 @@ struct Plater::priv
     void split_object();
     void split_volume();
     void schedule_background_process();
+    // Update background processing thread from the current config and Model.
+    enum UpdateBackgroundProcessReturnState {
+        // update_background_process() reports, that the Print / SLAPrint was updated in a way,
+        // that the background process was invalidated and it needs to be re-run.
+        UPDATE_BACKGROUND_PROCESS_RESTART = 1,
+        // update_background_process() reports, that the Print / SLAPrint was updated in a way,
+        // that a scene needs to be refreshed (you should call _3DScene::reload_scene(canvas3D, false))
+        UPDATE_BACKGROUND_PROCESS_REFRESH_SCENE = 2,   
+        // update_background_process() reports, that the Print / SLAPrint is invalid, and the error message
+        // was sent to the status line.
+        UPDATE_BACKGROUND_PROCESS_INVALID = 4,
+    };
+    // returns bit mask of UpdateBackgroundProcessReturnState
+    unsigned int update_background_process();
     void async_apply_config();
-    void start_background_process();
     void reload_from_disk();
     void export_object_stl();
     void fix_through_netfabb(const int obj_idx);
@@ -988,7 +1001,7 @@ Plater::priv::priv(Plater *q, MainFrame *main_frame) :
     background_process.set_sliced_event(EVT_SLICING_COMPLETED);
     background_process.set_finished_event(EVT_PROCESS_COMPLETED);
 	// Default printer technology for default config.
-    background_process.select_technology(q->printer_technology());
+    background_process.select_technology(this->printer_technology);
     // Register progress callback from the Print class to the Platter.
     print.set_status_callback([this](int percent, const std::string &message) {
         wxCommandEvent event(EVT_PROGRESS_BAR);
@@ -1009,6 +1022,7 @@ Plater::priv::priv(Plater *q, MainFrame *main_frame) :
     // XXX: more config from 3D.pm
     _3DScene::set_model(canvas3D, &model);
     _3DScene::set_print(canvas3D, &print);
+    _3DScene::set_SLA_print(canvas3D, &sla_print);
     _3DScene::set_config(canvas3D, config);
     _3DScene::enable_gizmos(canvas3D, true);
     _3DScene::enable_toolbar(canvas3D, true);
@@ -1091,6 +1105,11 @@ void Plater::priv::update(bool force_autocenter)
         model.center_instances_around_point(bed_center);
     }
 
+    if (this->printer_technology == ptSLA) {
+        // Update the SLAPrint from the current Model, so that the reload_scene()
+        // pulls the correct data.
+        this->update_background_process();
+    }
     _3DScene::reload_scene(canvas3D, false);
     preview->reset_gcode_preview_data();
     preview->reload_print();
@@ -1610,10 +1629,18 @@ void Plater::priv::schedule_background_process()
     this->background_process_timer.Start(500, wxTIMER_ONE_SHOT);
 }
 
-void Plater::priv::async_apply_config()
+// Update background processing thread from the current config and Model.
+// Returns a bitmask of UpdateBackgroundProcessReturnState.
+unsigned int Plater::priv::update_background_process()
 {
+    // bitmap of enum UpdateBackgroundProcessReturnState
+    unsigned int return_state = 0;
+
+    // If the async_apply_config() was not called by the timer, kill the timer, so the async_apply_config()
+    // will not be called again in vain.
+    this->background_process_timer.Stop();
+
     DynamicPrintConfig config = wxGetApp().preset_bundle->full_config();
-    auto            printer_technology = config.opt_enum<PrinterTechnology>("printer_technology");
     BoundingBox     bed_box_2D = get_extents(Polygon::new_scale(config.opt<ConfigOptionPoints>("bed_shape")->values));
     BoundingBoxf3   print_volume(unscale(bed_box_2D.min(0), bed_box_2D.min(1), 0.0), unscale(bed_box_2D.max(0), bed_box_2D.max(1), scale_(config.opt_float("max_print_height"))));
     // Allow the objects to protrude below the print bed, only the part of the object above the print bed will be sliced.
@@ -1634,40 +1661,55 @@ void Plater::priv::async_apply_config()
         // Reset preview canvases. If the print has been invalidated, the preview canvases will be cleared.
         // Otherwise they will be just refreshed.
         this->gcode_preview_data.reset();
-        if (printer_technology == ptFFF) {
+        switch (this->printer_technology) {
+        case ptFFF:
             if (this->preview != nullptr)
+                // If the preview is not visible, the following line just invalidates the preview,
+                // but the G-code paths are calculated first once the preview is made visible.
                 this->preview->reload_print();
             // We also need to reload 3D scene because of the wipe tower preview box
             if (this->config->opt_bool("wipe_tower")) {
     //            std::vector<int> selections = this->collect_selections();
     //            Slic3r::_3DScene::set_objects_selections(this->canvas3D, selections);
-    //            Slic3r::_3DScene::reload_scene(this->canvas3D, 1);
+                return_state |= UPDATE_BACKGROUND_PROCESS_REFRESH_SCENE;
             }
+            break;
+        case ptSLA:
+            //FIXME as of now the Print::APPLY_STATUS_INVALIDATED is not reliable, and
+            // currently the scene refresh is expensive and loses selection.
+            //return_state |= UPDATE_BACKGROUND_PROCESS_REFRESH_SCENE;
+            break;
         }
     }
-    if (invalidated != Print::APPLY_STATUS_UNCHANGED && this->get_config("background_processing") == "1" &&
-        this->background_process.start())
-		this->statusbar()->set_cancel_callback([this]() {
-            this->statusbar()->set_status_text(L("Cancelling"));
-			this->background_process.stop();
-        });
+
+    if (! this->background_process.empty()) {
+        std::string err = this->background_process.validate();
+        if (err.empty()) {
+            if (invalidated != Print::APPLY_STATUS_UNCHANGED)
+                return_state |= UPDATE_BACKGROUND_PROCESS_RESTART;
+        } else {
+            // The print is not valid.
+            GUI::show_error(this->q, _(err));
+            return_state |= UPDATE_BACKGROUND_PROCESS_INVALID;
+        }
+    }
+    return return_state;
 }
 
-void Plater::priv::start_background_process()
+void Plater::priv::async_apply_config()
 {
-	if (this->background_process.running())
-		return;
-    // Don't start process thread if Print is not valid.
-    std::string err = this->background_process.validate();
-    if (! err.empty()) {
-        this->statusbar()->set_status_text(err);
-	} else {
-		// Copy the names of active presets into the placeholder parser.
-        //FIXME how to generate a file name for the SLA printers?
-		wxGetApp().preset_bundle->export_selections(this->q->print().placeholder_parser());
-		// Start the background process.
-		this->background_process.start();
-	}
+    // bitmask of UpdateBackgroundProcessReturnState
+    unsigned int state = this->update_background_process();
+    if (state & UPDATE_BACKGROUND_PROCESS_REFRESH_SCENE)
+        _3DScene::reload_scene(canvas3D, false);
+    if ((state & UPDATE_BACKGROUND_PROCESS_RESTART) != 0 && this->get_config("background_processing") == "1") {
+        // The print is valid and it can be started.
+        if (this->background_process.start())
+            this->statusbar()->set_cancel_callback([this]() {
+                this->statusbar()->set_status_text(L("Cancelling"));
+                this->background_process.stop();
+            });
+    }
 }
 
 void Plater::priv::reload_from_disk()
@@ -1716,6 +1758,13 @@ void Plater::priv::on_notebook_changed(wxBookCtrlEvent&)
     const auto current_id = notebook->GetCurrentPage()->GetId();
     if (current_id == canvas3D->GetId()) {
         if (_3DScene::is_reload_delayed(canvas3D)) {
+            // Delayed loading of the 3D scene.
+            if (this->printer_technology == ptSLA) {
+                // Update the SLAPrint from the current Model, so that the reload_scene()
+                // pulls the correct data.
+                if (this->update_background_process() & UPDATE_BACKGROUND_PROCESS_RESTART)
+                    this->schedule_background_process();
+            }
             _3DScene::reload_scene(canvas3D, true);
         }
         // sets the canvas as dirty to force a render at the 1st idle event (wxWidgets IsShownOnScreen() is buggy and cannot be used reliably)
@@ -1811,22 +1860,18 @@ void Plater::priv::on_process_completed(wxCommandEvent &evt)
     //$self->object_list_changed;
     
     // refresh preview
-    if (this->preview != nullptr)
-        this->preview->reload_print();
-
-    // TODO: this needs to be implemented somehow
-    if(q->printer_technology() == PrinterTechnology::ptSLA) {
-
-        class Renderer: public SLASupportRenderer {
-        public:
-            void add_pillar(const Mesh&, ClickCb ) override {}
-            void add_head(const Mesh&, ClickCb) override {}
-            void add_bridge(const Mesh&, ClickCb) override {}
-            void add_junction(const Mesh&, ClickCb) override {}
-            void add_pad(const Mesh&, ClickCb) override {}
-        } renderer;
-
-        sla_print.render_supports(renderer);
+    switch (this->printer_technology) {
+    case ptFFF:
+        if (this->preview != nullptr)
+            this->preview->reload_print();
+        break;
+    case ptSLA:
+        // Update the SLAPrint from the current Model, so that the reload_scene()
+        // pulls the correct data.
+        if (this->update_background_process() & UPDATE_BACKGROUND_PROCESS_RESTART)
+            this->schedule_background_process();
+        _3DScene::reload_scene(canvas3D, true);
+        break;
     }
 }
 
@@ -2264,21 +2309,24 @@ void Plater::export_3mf()
     }
 }
 
-
 void Plater::reslice()
 {
-    // explicitly cancel a previous thread and start a new one.
-    // Don't reslice if export of G-code or sending to OctoPrint is running.
-//    if (! defined($self->{export_gcode_output_file}) && ! defined($self->{send_gcode_file})) {
-    // Stop the background processing threads, stop the async update timer.
-//    this->p->stop_background_process();
-    // Rather perform one additional unnecessary update of the print object instead of skipping a pending async update.
-    this->p->async_apply_config();
-	this->p->statusbar()->set_cancel_callback([this]() {
-		this->p->statusbar()->set_status_text(L("Cancelling"));
-		this->p->background_process.stop();
-    });
-    this->p->start_background_process();
+    //FIXME Don't reslice if export of G-code or sending to OctoPrint is running.
+    // bitmask of UpdateBackgroundProcessReturnState
+    unsigned int state = this->p->update_background_process();
+    if (state & priv::UPDATE_BACKGROUND_PROCESS_REFRESH_SCENE)
+        _3DScene::reload_scene(this->p->canvas3D, false);
+	if ((state & priv::UPDATE_BACKGROUND_PROCESS_INVALID) == 0 && !this->p->background_process.running()) {
+        // The print is valid and it can be started.
+        // Copy the names of active presets into the placeholder parser.
+        //FIXME how to generate a file name for the SLA printers?
+        wxGetApp().preset_bundle->export_selections(this->print().placeholder_parser());
+        if (this->p->background_process.start())
+			this->p->statusbar()->set_cancel_callback([this]() {
+				this->p->statusbar()->set_status_text(L("Cancelling"));
+				this->p->background_process.stop();
+            });
+    }
 }
 
 void Plater::send_gcode()
@@ -2317,8 +2365,10 @@ void Plater::on_config_change(const DynamicPrintConfig &config)
     bool update_scheduled = false;
     for (auto opt_key : p->config->diff(config)) {
         p->config->set_key_value(opt_key, config.option(opt_key)->clone());
-        if (opt_key == "printer_technology")
-			p->background_process.select_technology(config.opt_enum<PrinterTechnology>(opt_key));
+        if (opt_key == "printer_technology") {
+            p->printer_technology = config.opt_enum<PrinterTechnology>(opt_key);
+			p->background_process.select_technology(this->printer_technology());
+        }
         else if (opt_key  == "bed_shape") {
             if (p->canvas3D) _3DScene::set_bed_shape(p->canvas3D, p->config->option<ConfigOptionPoints>(opt_key)->values);
             if (p->preview) p->preview->set_bed_shape(p->config->option<ConfigOptionPoints>(opt_key)->values);
@@ -2384,7 +2434,7 @@ wxGLCanvas* Plater::canvas3D()
 
 PrinterTechnology Plater::printer_technology() const
 {
-    return wxGetApp().preset_bundle->printers.get_edited_preset().printer_technology();
+    return p->printer_technology;
 }
 
 void Plater::changed_object(int obj_idx)