add "overhang_reverse_internal_only"

src/libslic3r/PerimeterGenerator.cpp

@@ -1228,14 +1228,24 @@ void PerimeterGenerator::add_infill_contour_for_arachne(ExPolygons infill_contou
 
 
 //w38
-static void reorient_perimeters(ExtrusionEntityCollection &entities, bool steep_overhang_contour, bool steep_overhang_hole)
+static void reorient_perimeters(ExtrusionEntityCollection &entities, bool steep_overhang_contour, bool steep_overhang_hole, bool reverse_internal_only)
 {
     if (steep_overhang_hole || steep_overhang_contour) {
         for (auto entity : entities) {
             if (entity->is_loop()) {
                 ExtrusionLoop *eloop = static_cast<ExtrusionLoop *>(entity);
                 bool need_reverse = ((eloop->loop_role() & elrHole) == elrHole) ? steep_overhang_hole : steep_overhang_contour;
-                if (need_reverse) {
+                bool           isExternal   = false;
+                if (reverse_internal_only) {
+                    for (auto path : eloop->paths) {
+                        if (path.role().is_external_perimeter()) {
+                            isExternal = true;
+                            break;
+                        }
+                    }
+                }
+
+                if (need_reverse && !isExternal) {
                     eloop->make_clockwise();
                 }
             }
@@ -1453,7 +1463,7 @@ void PerimeterGenerator::process_arachne(
     if (ExtrusionEntityCollection extrusion_coll = traverse_extrusions(params, lower_slices_polygons_cache, ordered_extrusions,
                                                                        steep_overhang_contour, steep_overhang_hole);
         !extrusion_coll.empty()) {
-        reorient_perimeters(extrusion_coll, steep_overhang_contour, steep_overhang_hole);
+        reorient_perimeters(extrusion_coll, steep_overhang_contour, steep_overhang_hole, params.config.overhang_reverse_internal_only);
         out_loops.append(extrusion_coll);
     }
 
@@ -1797,7 +1807,7 @@ void PerimeterGenerator::process_with_one_wall_arachne(
     if (ExtrusionEntityCollection extrusion_coll = traverse_extrusions(params, lower_slices_polygons_cache, ordered_extrusions,
                                                                        steep_overhang_contour, steep_overhang_hole);
         !extrusion_coll.empty()) {
-        reorient_perimeters(extrusion_coll, steep_overhang_contour, steep_overhang_hole);
+        reorient_perimeters(extrusion_coll, steep_overhang_contour, steep_overhang_hole, params.config.overhang_reverse_internal_only);
         out_loops.append(extrusion_coll);
     }
 
@@ -2194,7 +2204,7 @@ void PerimeterGenerator::process_classic(
         bool                      steep_overhang_contour = false;
         bool                      steep_overhang_hole    = false;
         ExtrusionEntityCollection entities = traverse_loops_classic(params, lower_layer_polygons_cache, contours.front(), thin_walls,steep_overhang_contour, steep_overhang_hole);
-        reorient_perimeters(entities, steep_overhang_contour, steep_overhang_hole);
+        reorient_perimeters(entities, steep_overhang_contour, steep_overhang_hole, params.config.overhang_reverse_internal_only);
         // if brim will be printed, reverse the order of perimeters so that
         // we continue inwards after having finished the brim
         // TODO: add test for perimeter order

src/libslic3r/Preset.cpp

@@ -496,7 +496,7 @@ static std::vector<std::string> s_Preset_print_options {
     //w33
     ,"ironing_pattern"
     //w38
-    ,"overhang_reverse","overhang_reverse_threshold"};
+    ,"overhang_reverse","overhang_reverse_internal_only","overhang_reverse_threshold"};
 
 static std::vector<std::string> s_Preset_filament_options {
     "filament_colour", "filament_diameter", "filament_type", "filament_soluble", "filament_notes", "filament_max_volumetric_speed",

src/libslic3r/PrintConfig.cpp

@@ -2317,6 +2317,18 @@ void PrintConfigDef::init_fff_params()
     def->mode       = comAdvanced;
     def->set_default_value(new ConfigOptionBool(false));
 
+    def             = this->add("overhang_reverse_internal_only", coBool);
+    def->label      = L("Reverse only internal perimeters");
+    def->category   = L("Layers and Perimeters");
+    def->tooltip    = L("Apply the reverse perimeters logic only on internal perimeters. \n\nThis setting greatly reduces part stresses as "
+                     "they are now distributed in alternating directions. This should reduce part warping while also maintaining external "
+                     "wall quality. This feature can be very useful for warp prone material, like ABS/ASA, and also for elastic filaments, "
+                     "like TPU and Silk PLA. It can also help reduce warping on floating regions over supports.\n\nFor this setting to be "
+                     "the most effective, it is recomended to set the Reverse Threshold to 0 so that all internal walls print in "
+                     "alternating directions on odd layers irrespective of their overhang degree.");
+    def->mode       = comAdvanced;
+    def->set_default_value(new ConfigOptionBool(false));
+
     //w38
     def              = this->add("overhang_reverse_threshold", coFloatOrPercent);
     def->label       = L("Reverse threshold");

src/libslic3r/PrintConfig.hpp

@@ -678,6 +678,7 @@ PRINT_CONFIG_CLASS_DEFINE(
 
     //w38
     ((ConfigOptionBool,                 overhang_reverse))
+    ((ConfigOptionBool, overhang_reverse_internal_only))
     ((ConfigOptionFloatOrPercent,       overhang_reverse_threshold))
 )
 

src/libslic3r/PrintObject.cpp

@@ -876,7 +876,11 @@ bool PrintObject::invalidate_state_by_config_options(
             //w17
             || opt_key == "top_area_threshold"
             //w23
-            || opt_key == "only_one_wall_first_layer") {
+            || opt_key == "only_one_wall_first_layer"
+            //w38
+            || opt_key == "overhang_reverse"
+            || opt_key == "overhang_reverse_internal_only"
+            || opt_key == "overhang_reverse_threshold") {
             steps.emplace_back(posSlice);
         } else if (
                opt_key == "seam_position"

src/slic3r/GUI/ConfigManipulation.cpp

@@ -385,6 +385,7 @@ void ConfigManipulation::toggle_print_fff_options(DynamicPrintConfig* config)
     bool has_overhang_reverse     = config->opt_bool("overhang_reverse");
     bool allow_overhang_reverse   = has_detect_overhang_wall && !has_spiral_vase;
     toggle_field("overhang_reverse", allow_overhang_reverse);
+    toggle_field("overhang_reverse_internal_only", allow_overhang_reverse && has_overhang_reverse);
     toggle_field("overhang_reverse_threshold", allow_overhang_reverse && has_overhang_reverse);
 }
 

src/slic3r/GUI/Tab.cpp

@@ -1462,6 +1462,7 @@ void TabPrint::build()
 
         //w38
         optgroup->append_single_option_line("overhang_reverse");
+        optgroup->append_single_option_line("overhang_reverse_internal_only");
         optgroup->append_single_option_line("overhang_reverse_threshold");
 
         optgroup = page->new_optgroup(L("Advanced"));