Organic supports: Adding bridge detection using the same algorithms

as the regular supports.
Partial fix to #9493

src/libslic3r/ClipperUtils.hpp

@@ -361,6 +361,8 @@ inline Slic3r::Polygons   expand(const Slic3r::Polygon &polygon, const float del
     { assert(delta > 0); return offset(polygon, delta, joinType, miterLimit); }
 inline Slic3r::Polygons   expand(const Slic3r::Polygons &polygons, const float delta, ClipperLib::JoinType joinType = DefaultJoinType, double miterLimit = DefaultMiterLimit) 
     { assert(delta > 0); return offset(polygons, delta, joinType, miterLimit); }
+inline Slic3r::Polygons   expand(const Slic3r::ExPolygons &polygons, const float delta, ClipperLib::JoinType joinType = DefaultJoinType, double miterLimit = DefaultMiterLimit) 
+    { assert(delta > 0); return offset(polygons, delta, joinType, miterLimit); }
 inline Slic3r::ExPolygons expand_ex(const Slic3r::Polygons &polygons, const float delta, ClipperLib::JoinType joinType = DefaultJoinType, double miterLimit = DefaultMiterLimit) 
     { assert(delta > 0); return offset_ex(polygons, delta, joinType, miterLimit); }
 // Input polygons for shrinking shall be "normalized": There must be no overlap / intersections between the input polygons.

src/libslic3r/SupportMaterial.cpp

@@ -1260,20 +1260,20 @@ namespace SupportMaterialInternal {
                 collect_bridging_perimeter_areas(*static_cast<const ExtrusionLoop*>(ee), expansion_scaled, out);
         }
     }
+}
 
-    static void remove_bridges_from_contacts(
+void remove_bridges_from_contacts(
     const PrintConfig   &print_config, 
     const Layer         &lower_layer,
-        const Polygons      &lower_layer_polygons,
     const LayerRegion   &layerm,
     float                fw, 
     Polygons            &contact_polygons)
-    {
+{
     // compute the area of bridging perimeters
     Polygons bridges;
     {
         // Surface supporting this layer, expanded by 0.5 * nozzle_diameter, as we consider this kind of overhang to be sufficiently supported.
-            Polygons lower_grown_slices = expand(lower_layer_polygons,
+        Polygons lower_grown_slices = expand(lower_layer.lslices,
             //FIXME to mimic the decision in the perimeter generator, we should use half the external perimeter width.
             0.5f * float(scale_(print_config.nozzle_diameter.get_at(layerm.region().config().perimeter_extruder-1))),
             SUPPORT_SURFACES_OFFSET_PARAMETERS);
@@ -1340,7 +1340,6 @@ namespace SupportMaterialInternal {
               { { union_ex(contact_polygons) },            { "contact_polygons",           "blue",   0.5f } },
               { { union_ex(bridges) },                     { "bridges",                    "red",    "black", "", scaled<coord_t>(0.1f), 0.5f } } });
     #endif /* SLIC3R_DEBUG */
-    }
 }
 
 std::vector<Polygons> PrintObjectSupportMaterial::buildplate_covered(const PrintObject &object) const
@@ -1558,8 +1557,7 @@ static inline std::tuple<Polygons, Polygons, Polygons, float> detect_overhangs(
 
             if (object_config.dont_support_bridges)
                 //FIXME Expensive, potentially not precise enough. Misses gap fill extrusions, which bridge.
-                SupportMaterialInternal::remove_bridges_from_contacts(
+                remove_bridges_from_contacts(print_config, lower_layer, *layerm, fw, diff_polygons);
-                    print_config, lower_layer, lower_layer_polygons, *layerm, fw, diff_polygons);
 
             if (diff_polygons.empty())
                 continue;

src/libslic3r/SupportMaterial.hpp

@@ -147,6 +147,15 @@ struct SupportParameters {
     bool                    with_sheath;
 };
 
+// Remove bridges from support contact areas.
+// To be called if PrintObjectConfig::dont_support_bridges.
+void remove_bridges_from_contacts(
+    const PrintConfig   &print_config, 
+    const Layer         &lower_layer,
+    const LayerRegion   &layerm,
+    float                fw, 
+    Polygons            &contact_polygons);
+
 // Generate raft layers, also expand the 1st support layer
 // in case there is no raft layer to improve support adhesion.
 SupportGeneratorLayersPtr generate_raft_base(

src/libslic3r/TreeSupport.cpp

@@ -226,6 +226,7 @@ void tree_supports_show_error(std::string_view message, bool critical)
 {
     std::vector<Polygons> out(print_object.layer_count(), Polygons{});
 
+    const PrintConfig       &print_config           = print_object.print()->config();
     const PrintObjectConfig &config                 = print_object.config();
     const bool               support_auto           = config.support_material.value && config.support_material_auto.value;
     const int                support_enforce_layers = config.support_material_enforce_layers.value;
@@ -242,7 +243,8 @@ void tree_supports_show_error(std::string_view message, bool critical)
 
     size_t num_overhang_layers = support_auto ? out.size() : std::max(size_t(support_enforce_layers), enforcers_layers.size());
     tbb::parallel_for(tbb::blocked_range<LayerIndex>(1, num_overhang_layers),
-        [&print_object, &enforcers_layers, &blockers_layers, support_auto, support_enforce_layers, support_threshold_auto, tan_threshold, enforcer_overhang_offset, &throw_on_cancel, &out]
+        [&print_object, &config, &print_config, &enforcers_layers, &blockers_layers, 
+         support_auto, support_enforce_layers, support_threshold_auto, tan_threshold, enforcer_overhang_offset, &throw_on_cancel, &out]
         (const tbb::blocked_range<LayerIndex> &range) {
         for (LayerIndex layer_id = range.begin(); layer_id < range.end(); ++ layer_id) {
             const Layer   &current_layer  = *print_object.get_layer(layer_id);
@@ -275,6 +277,11 @@ void tree_supports_show_error(std::string_view message, bool critical)
                 }
                 if (! (enforced_layer || blockers_layers.empty() || blockers_layers[layer_id].empty()))
                     overhangs = diff(overhangs, blockers_layers[layer_id], ApplySafetyOffset::Yes);
+                if (config.dont_support_bridges) {
+                    for (const LayerRegion *layerm : current_layer.regions())
+                        remove_bridges_from_contacts(print_config, lower_layer, *layerm, 
+                            float(layerm->flow(frExternalPerimeter).scaled_width()), overhangs);
+                }
             }
             //check_self_intersections(overhangs, "generate_overhangs1");
             if (! enforcers_layers.empty() && ! enforcers_layers[layer_id].empty()) {