[Feature] Introduced option to control amount of internal bridging, fixing internal bridge missing for some sloped surfaces

src/libslic3r/Preset.cpp

@@ -786,7 +786,7 @@ static std::vector<std::string> s_Preset_print_options {
     "independent_support_layer_height",
     "support_angle", "support_interface_top_layers", "support_interface_bottom_layers",
     "support_interface_pattern", "support_interface_spacing", "support_interface_loop_pattern",
-    "support_top_z_distance", "support_on_build_plate_only","support_critical_regions_only", "bridge_no_support", "thick_bridges", "thick_internal_bridges", "max_bridge_length", "print_sequence", "support_remove_small_overhang",
+    "support_top_z_distance", "support_on_build_plate_only","support_critical_regions_only", "bridge_no_support", "thick_bridges", "thick_internal_bridges","dont_filter_internal_bridges", "max_bridge_length", "print_sequence", "support_remove_small_overhang",
     "filename_format", "wall_filament", "support_bottom_z_distance",
     "sparse_infill_filament", "solid_infill_filament", "support_filament", "support_interface_filament","support_interface_not_for_body",
     "ooze_prevention", "standby_temperature_delta", "interface_shells", "line_width", "initial_layer_line_width",

src/libslic3r/PrintConfig.cpp

@@ -1219,6 +1219,13 @@ void PrintConfigDef::init_fff_params()
                        "consider turning it off if you are using large nozzles.");
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionBool(true));
+
+    def = this->add("dont_filter_internal_bridges", coBool);
+    def->label = L("Don't filter out small internal bridges");
+    def->category = L("Quality");
+    def->tooltip  = L("This option can help reducing pillowing on top surfaces in heavily slanted or curved models.\n\nBy default, small internal bridges are filtered out and the internal solid infill is printed directly over the sparse infill. This works well in most cases, speeding up printing without too much compromise in top surface quality. \n\nHowever, in heavily slanted or curved models or where too low sparse infill density is used this may result in curling of the unsupported solid infill, causing pillowing.\n\n Enabling this option will always print a bridge layer over sparse infill.");
+    def->mode = comAdvanced;
+    def->set_default_value(new ConfigOptionBool(false));
 
 
     def = this->add("max_bridge_length", coFloat);

src/libslic3r/PrintConfig.hpp

@@ -744,6 +744,7 @@ PRINT_CONFIG_CLASS_DEFINE(
     // Orca internal thick bridge
     ((ConfigOptionBool,                thick_bridges))
     ((ConfigOptionBool,                thick_internal_bridges))
+    ((ConfigOptionBool,                dont_filter_internal_bridges))
     // Overhang angle threshold.
     ((ConfigOptionInt,                 support_threshold_angle))
     ((ConfigOptionFloat,               support_object_xy_distance))

src/libslic3r/PrintObject.cpp

@@ -1967,7 +1967,6 @@ template<typename T> void debug_draw(std::string name, const T& a, const T& b, c
 void PrintObject::bridge_over_infill()
 {
     BOOST_LOG_TRIVIAL(info) << "Bridge over infill - Start" << log_memory_info();
-
     struct CandidateSurface
     {
         CandidateSurface(const Surface     *original_surface,
@@ -1989,12 +1988,20 @@ void PrintObject::bridge_over_infill()
     };
 
     std::map<size_t, std::vector<CandidateSurface>> surfaces_by_layer;
+    // Ioannis Giannakas:
+    // Detect use of lightning infill. Moved earlier in the function to pass to the gather and filter surfaces threads.
+    bool has_lightning_infill = false;
+    for (size_t i = 0; i < this->num_printing_regions(); i++) {
+        if (this->printing_region(i).config().sparse_infill_pattern == ipLightning) {
+            has_lightning_infill = true;
+            break;
+        }
+    }
 
     // SECTION to gather and filter surfaces for expanding, and then cluster them by layer
     {
         tbb::concurrent_vector<CandidateSurface> candidate_surfaces;
-        tbb::parallel_for(tbb::blocked_range<size_t>(0, this->layers().size()), [po = static_cast<const PrintObject *>(this),
-                                                                                 &candidate_surfaces](tbb::blocked_range<size_t> r) {
+        tbb::parallel_for(tbb::blocked_range<size_t>(0, this->layers().size()), [po = static_cast<const PrintObject *>(this), &candidate_surfaces, has_lightning_infill](tbb::blocked_range<size_t> r) {
             PRINT_OBJECT_TIME_LIMIT_MILLIS(PRINT_OBJECT_TIME_LIMIT_DEFAULT);
             for (size_t lidx = r.begin(); lidx < r.end(); lidx++) {
                 const Layer *layer = po->get_layer(lidx);
@@ -2017,14 +2024,18 @@ void PrintObject::bridge_over_infill()
                     }
                 }
                 unsupported_area = closing(unsupported_area, float(SCALED_EPSILON));
-                // By expanding the lower layer solids, we avoid making bridges from the tiny internal overhangs that are (very likely) supported by previous layer solids
-                // NOTE that we cannot filter out polygons worth bridging by their area, because sometimes there is a very small internal island that will grow into large hole
-                lower_layer_solids = shrink(lower_layer_solids, 1 * spacing); // first remove thin regions that will not support anything
-                lower_layer_solids = expand(lower_layer_solids, (1 + 3) * spacing); // then expand back (opening), and further for parts supported by internal solids
-                // By shrinking the unsupported area, we avoid making bridges from narrow ensuring region along perimeters.
-                unsupported_area   = shrink(unsupported_area, 3 * spacing);
-                unsupported_area   = diff(unsupported_area, lower_layer_solids);
-
+
+                // Ioannis Giannakas:
+                // Lightning infill benefits from always having a bridge layer so don't filter out small unsupported areas. Also, don't filter small internal unsupported areas if the user has requested so.
+                if(!has_lightning_infill && !po->config().dont_filter_internal_bridges){
+                    // By expanding the lower layer solids, we avoid making bridges from the tiny internal overhangs that are (very likely) supported by previous layer solids
+                    // NOTE that we cannot filter out polygons worth bridging by their area, because sometimes there is a very small internal island that will grow into large hole
+                    lower_layer_solids = shrink(lower_layer_solids, 1 * spacing); // first remove thin regions that will not support anything
+                    lower_layer_solids = expand(lower_layer_solids, (1 + 3) * spacing); // then expand back (opening), and further for parts supported by internal solids
+                    // By shrinking the unsupported area, we avoid making bridges from narrow ensuring region along perimeters.
+                    unsupported_area   = shrink(unsupported_area, 3 * spacing);
+                    unsupported_area   = diff(unsupported_area, lower_layer_solids);
+                }
                 for (const LayerRegion *region : layer->regions()) {
                     SurfacesPtr region_internal_solids = region->fill_surfaces.filter_by_type(stInternalSolid);
                     for (const Surface *s : region_internal_solids) {
@@ -2069,13 +2080,6 @@ void PrintObject::bridge_over_infill()
     // LIGHTNING INFILL SECTION - If lightning infill is used somewhere, we check the areas that are going to be bridges, and those that rely on the 
     // lightning infill under them get expanded. This somewhat helps to ensure that most of the extrusions are anchored to the lightning infill at the ends.
     // It requires modifying this instance of print object in a specific way, so that we do not invalidate the pointers in our surfaces_by_layer structure.
-    bool has_lightning_infill = false;
-    for (size_t i = 0; i < this->num_printing_regions(); i++) {
-        if (this->printing_region(i).config().sparse_infill_pattern == ipLightning) {
-            has_lightning_infill = true;
-            break;
-        }
-    }
     if (has_lightning_infill) {
         // Prepare backup data for the Layer Region infills. Before modfiyng the layer region, we backup its fill surfaces by moving! them into this map.
         // then a copy is created, modifiyed and passed to lightning infill generator. After generator is created, we restore the original state of the fills

src/slic3r/GUI/Tab.cpp

@@ -1976,6 +1976,7 @@ void TabPrint::build()
         optgroup->append_single_option_line("bridge_density");
         optgroup->append_single_option_line("thick_bridges");
         optgroup->append_single_option_line("thick_internal_bridges");
+        optgroup->append_single_option_line("dont_filter_internal_bridges");
 
         optgroup = page->new_optgroup(L("Overhangs"), L"param_advanced");
         optgroup->append_single_option_line("detect_overhang_wall");