Fix of disabling thick bridges adds unnecessary support interfaces #7260

Improved numerical robustness when removing bridging perimeters from
overhangs to be supported.

1 files changed, 5 insertions, 2 deletions

diff --git a/src/libslic3r/SupportMaterial.cpp b/src/libslic3r/SupportMaterial.cpp
index 8a04b6439..1f3ecfa12 100644
--- a/src/libslic3r/SupportMaterial.cpp
+++ b/src/libslic3r/SupportMaterial.cpp
@@ -1340,7 +1340,10 @@ namespace SupportMaterialInternal {
             // so we take the largest value and also apply safety offset to be ensure no gaps
             // are left in between
             Flow perimeter_bridge_flow = layerm.bridging_flow(frPerimeter);
-            float w = float(std::max(perimeter_bridge_flow.scaled_width(), perimeter_bridge_flow.scaled_spacing()));
+            //FIXME one may want to use a maximum of bridging flow width and normal flow width, as the perimeters are calculated using the normal flow
+            // and then turned to bridging flow, thus their centerlines are derived from non-bridging flow and expanding them by a bridging flow
+            // may not expand them to the edge of their respective islands.
+            const float w = float(0.5 * std::max(perimeter_bridge_flow.scaled_width(), perimeter_bridge_flow.scaled_spacing())) + scaled<float>(0.001);
             for (Polyline &polyline : overhang_perimeters)
                 if (polyline.is_straight()) {
                     // This is a bridge 
@@ -1355,7 +1358,7 @@ namespace SupportMaterialInternal {
                                 supported[j] = true;
                     if (supported[0] && supported[1])
                         // Offset a polyline into a thick line.
-                        polygons_append(bridges, offset(polyline, 0.5f * w + 10.f));
+                        polygons_append(bridges, offset(polyline, w));
                 }
             bridges = union_(bridges);
         }