new option: Overlapping perimeters, for when you don't care and don't want to use MedialAxis algo

#116

src/libslic3r/Layer.cpp

@@ -137,6 +137,7 @@ void Layer::make_perimeters()
                 && config.opt_serialize("external_perimeter_extrusion_width").compare(other_config.opt_serialize("external_perimeter_extrusion_width")) == 0
                 && config.thin_walls                == other_config.thin_walls
                 && config.thin_walls_min_width      == other_config.thin_walls_min_width
+                && config.thin_perimeters           == other_config.thin_perimeters
                 && config.thin_walls_overlap        == other_config.thin_walls_overlap
                 && config.external_perimeters_first == other_config.external_perimeters_first
                 && config.infill_overlap            == other_config.infill_overlap

src/libslic3r/PerimeterGenerator.cpp

@@ -351,22 +351,21 @@ void PerimeterGenerator::process()
                 //this variable stored the next onion
                 ExPolygons next_onion;
                 if (i == 0) {
-                    // compute next onion, without taking care of thin_walls : destroy too thin areas.
+                    // compute next onion
-                    if (!this->config->thin_walls)
-                        next_onion = offset2_ex(
-                            last,
-                            -(float)(ext_perimeter_width / 2 + ext_min_spacing / 2 - 1),
-                            +(float)(ext_min_spacing / 2 - 1));
-
-
-                    // look for thin walls
-                    if (this->config->thin_walls) {
                         // the minimum thickness of a single loop is:
                         // ext_width/2 + ext_spacing/2 + spacing/2 + width/2
+                    if (this->config->thin_perimeters)
+                        next_onion = offset_ex(
+                            last,
+                            -(float)(ext_perimeter_width / 2));
+                    else
                         next_onion = offset2_ex(
                             last,
                             -(float)(ext_perimeter_width / 2 + ext_min_spacing / 2 - 1),
                             +(float)(ext_min_spacing / 2 - 1));
+
+                    // look for thin walls
+                     if (this->config->thin_walls) {
                         // detect edge case where a curve can be split in multiple small chunks.
                         ExPolygons no_thin_onion = offset_ex(last, double( - ext_perimeter_width / 2));
                         float div = 2;

src/libslic3r/PrintConfig.cpp

@@ -2811,13 +2811,21 @@ void PrintConfigDef::init_fff_params()
     def->max = max_temp;
     def->set_default_value(new ConfigOptionInts { 200 });
 
+    def = this->add("thin_perimeters", coBool);
+    def->label = L("Overlapping perimeters");
+    def->full_label = L("Overlapping perimeters");
+    def->category = OptionCategory::perimeter;
+    def->tooltip = L("Allow external perimeter to overlap each other to avoid the use of thin walls. Note that their flow isn't adjusted and so it will result in over-extruding and undefined behavior.");
+    def->mode = comExpert;
+    def->set_default_value(new ConfigOptionBool(false));
+
     def = this->add("thin_walls", coBool);
     def->label = L("");
     def->full_label = L("Thin walls");
     def->category = OptionCategory::perimeter;
     def->tooltip = L("Detect single-width walls (parts where two extrusions don't fit and we need "
-                   "to collapse them into a single trace). If unchecked, slic3r may try to fit perimeters "
+        "to collapse them into a single trace). If unchecked, slic3r may try to fit perimeters "
-                   "where it's not possible, creating some overlap leading to over-extrusion.");
+        "where it's not possible, creating some overlap leading to over-extrusion.");
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionBool(true));
 

src/libslic3r/PrintConfig.hpp

@@ -629,6 +629,7 @@ public:
     ConfigOptionInt                 solid_infill_every_layers;
     ConfigOptionFloatOrPercent      solid_infill_speed;
     // Detect thin walls.
+    ConfigOptionBool                thin_perimeters;
     ConfigOptionBool                thin_walls;
     ConfigOptionFloatOrPercent      thin_walls_min_width;
     ConfigOptionFloatOrPercent      thin_walls_overlap;
@@ -696,6 +697,7 @@ protected:
         OPT_PTR(solid_infill_extrusion_width);
         OPT_PTR(solid_infill_every_layers);
         OPT_PTR(solid_infill_speed);
+        OPT_PTR(thin_perimeters);
         OPT_PTR(thin_walls);
         OPT_PTR(thin_walls_min_width);
         OPT_PTR(thin_walls_overlap);

src/libslic3r/PrintObject.cpp

@@ -595,6 +595,7 @@ bool PrintObject::invalidate_state_by_config_options(const std::vector<t_config_
             || opt_key == "first_layer_extrusion_width"
             || opt_key == "perimeter_extrusion_width"
             || opt_key == "infill_overlap"
+            || opt_key == "thin_perimeters"
             || opt_key == "thin_walls"
             || opt_key == "thin_walls_min_width"
             || opt_key == "thin_walls_overlap"

src/slic3r/GUI/Preset.cpp

@@ -381,7 +381,9 @@ const std::vector<std::string>& Preset::print_options()
         "layer_height", "first_layer_height", "perimeters", "spiral_vase", "slice_closing_radius", "top_solid_layers", "bottom_solid_layers", 
         "extra_perimeters",
         "extra_perimeters_odd_layers",
-        "only_one_perimeter_top", "ensure_vertical_shell_thickness", "avoid_crossing_perimeters", "thin_walls", "overhangs", 
+        "only_one_perimeter_top", "ensure_vertical_shell_thickness", "avoid_crossing_perimeters", 
+        "thin_perimeters",
+        "thin_walls", "overhangs", 
         "overhangs_width",
         "seam_position", 
         "external_perimeters_first", 

src/slic3r/GUI/Tab.cpp

@@ -1058,6 +1058,7 @@ void TabPrint::build()
 		optgroup->append_single_option_line("only_one_perimeter_top");
 		optgroup->append_single_option_line("ensure_vertical_shell_thickness");
 		optgroup->append_single_option_line("avoid_crossing_perimeters");
+		optgroup->append_single_option_line("thin_perimeters");
         line = { _(L("Thin walls")), "" };
         line.append_option(optgroup->get_option("thin_walls"));
         line.append_option(optgroup->get_option("thin_walls_min_width"));