medial axis: now grows the extrusion to nozzle diameter if it's lower than that. Add a parameter to define the min width (default to 33% of nozzle diameter).

src/libslic3r/Layer.cpp

@@ -110,6 +110,7 @@ void Layer::make_perimeters()
                 && config.overhangs         == other_config.overhangs
                 && config.serialize("perimeter_extrusion_width").compare(other_config.serialize("perimeter_extrusion_width")) == 0
                 && config.thin_walls == other_config.thin_walls
+                && config.thin_walls_min_width == other_config.thin_walls_min_width
                 && config.external_perimeters_first == other_config.external_perimeters_first
                 && config.perimeter_loop == other_config.perimeter_loop) {
                 layerms.push_back(other_layerm);

src/libslic3r/MedialAxis.cpp

@@ -578,7 +578,7 @@ MedialAxis::fusion_corners(ThickPolylines &pp)
         //FIXME: also pull (a bit less) points that are near to this one.
         // if true, pull it a bit, depends on my size, the dot?, and the coeff at my 0-end (~14% for a square, almost 0 for a gentle curve)
         coord_t length_pull = polyline.length();
-        length_pull *= 0.144 * get_coeff_from_angle_countour(polyline.points.back(), this->expolygon, min(min_width, polyline.length() / 2));
+        length_pull *= 0.144 * get_coeff_from_angle_countour(polyline.points.back(), this->expolygon, min(min_width, (coord_t)(polyline.length() / 2)));
 
         //compute dir
         Vec2d pull_direction(polyline.points[1].x() - polyline.points[0].x(), polyline.points[1].y() - polyline.points[0].y());
@@ -801,11 +801,11 @@ MedialAxis::main_fusion(ThickPolylines& pp)
                 //test if we don't merge with something too different and without any relevance.
                 double coeffSizePolyI = 1;
                 if (polyline.width.back() == 0) {
-                    coeffSizePolyI = 0.1 + 0.9*get_coeff_from_angle_countour(polyline.points.back(), this->expolygon, min(min_width, polyline.length() / 2));
+                    coeffSizePolyI = 0.1 + 0.9*get_coeff_from_angle_countour(polyline.points.back(), this->expolygon, min(min_width, (coord_t)(polyline.length() / 2)));
                 }
                 double coeffSizeOtherJ = 1;
                 if (other.width.back() == 0) {
-                    coeffSizeOtherJ = 0.1 + 0.9*get_coeff_from_angle_countour(other.points.back(), this->expolygon, min(min_width, polyline.length() / 2));
+                    coeffSizeOtherJ = 0.1 + 0.9*get_coeff_from_angle_countour(other.points.back(), this->expolygon, min(min_width, (coord_t)(polyline.length() / 2)));
                 }
                 //std::cout << " try2 : " << i << ":" << j << " : "
                 //    << (abs(polyline.length()*coeffSizePolyI - other.length()*coeffSizeOtherJ) > max_width / 2)
@@ -904,10 +904,10 @@ MedialAxis::main_fusion(ThickPolylines& pp)
                 //TODO: try if we can achieve a better result if we use a different algo if the angle is <90°
                 const double coeff_angle_poly = (coeff_angle_cache.find(polyline.points.back()) != coeff_angle_cache.end())
                     ? coeff_angle_cache[polyline.points.back()]
-                    : (get_coeff_from_angle_countour(polyline.points.back(), this->expolygon, min(min_width, polyline.length() / 2)));
+                    : (get_coeff_from_angle_countour(polyline.points.back(), this->expolygon, min(min_width, (coord_t)(polyline.length() / 2))));
                 const double coeff_angle_candi = (coeff_angle_cache.find(best_candidate->points.back()) != coeff_angle_cache.end())
                     ? coeff_angle_cache[best_candidate->points.back()]
-                    : (get_coeff_from_angle_countour(best_candidate->points.back(), this->expolygon, min(min_width, best_candidate->length() / 2)));
+                    : (get_coeff_from_angle_countour(best_candidate->points.back(), this->expolygon, min(min_width, (coord_t)(best_candidate->length() / 2))));
 
                 //this will encourage to follow the curve, a little, because it's shorter near the center
                 //without that, it tends to go to the outter rim.
@@ -1488,11 +1488,31 @@ MedialAxis::build(ThickPolylines* polylines_out)
     //    svg.draw(pp);
     //    svg.Close();
     //}
+    if (nozzle_diameter != min_width)
+        grow_to_nozzle_diameter(pp, diff_ex(this->bounds, this->expolygon));
 
     polylines_out->insert(polylines_out->end(), pp.begin(), pp.end());
 
 }
 
+
+void
+MedialAxis::grow_to_nozzle_diameter(ThickPolylines& pp, const ExPolygons& anchors) {
+    //ensure the width is not lower than 0.4.
+    for (ThickPolyline& polyline : pp) {
+        for (int i = 0; i < polyline.points.size(); ++i) {
+            bool is_anchored = false;
+            for (const ExPolygon &poly : anchors) {
+                if (poly.contains(polyline.points[i])) {
+                    is_anchored = true;
+                    break;
+                }
+            }
+            if (!is_anchored && polyline.width[i]<nozzle_diameter) polyline.width[i] = nozzle_diameter;
+        }
+    }
+}
+
 ExtrusionEntityCollection thin_variable_width(const ThickPolylines &polylines, ExtrusionRole role, Flow flow) {
     // this value determines granularity of adaptive width, as G-code does not allow
     // variable extrusion within a single move; this value shall only affect the amount

src/libslic3r/MedialAxis.hpp

@@ -21,12 +21,14 @@ namespace Slic3r {
         ExPolygon expolygon;
         const ExPolygon& bounds;
         const ExPolygon& surface;
-        const double max_width;
+        const coord_t max_width;
-        const double min_width;
+        const coord_t min_width;
-        const double height;
+        const coord_t height;
+        coord_t nozzle_diameter;
         bool stop_at_min_width = true;
-        MedialAxis(const ExPolygon &_expolygon, const ExPolygon &_bounds, const double _max_width, const double _min_width, const double _height)
+        MedialAxis(const ExPolygon &_expolygon, const ExPolygon &_bounds, const coord_t _max_width, const coord_t _min_width, const coord_t _height)
             : surface(_expolygon), bounds(_bounds), max_width(_max_width), min_width(_min_width), height(_height) {
+            nozzle_diameter = _min_width;
         };
         void build(ThickPolylines* polylines_out);
         void build(Polylines* polylines);
@@ -60,6 +62,7 @@ namespace Slic3r {
         void remove_too_thin_points(ThickPolylines& pp);
         void remove_too_short_polylines(ThickPolylines& pp, const coord_t min_size);
         void ensure_not_overextrude(ThickPolylines& pp);
+        void grow_to_nozzle_diameter(ThickPolylines& pp, const ExPolygons& anchors);
     };
 
     ExtrusionEntityCollection thin_variable_width(const ThickPolylines &polylines, ExtrusionRole role, Flow flow);

src/libslic3r/PerimeterGenerator.cpp

@@ -265,7 +265,7 @@ void PerimeterGenerator::process()
 
                         // the following offset2 ensures almost nothing in @thin_walls is narrower than $min_width
                         // (actually, something larger than that still may exist due to mitering or other causes)
-                        coord_t min_width = (coord_t)scale_(this->ext_perimeter_flow.nozzle_diameter / 3);
+                        coord_t min_width = (coord_t)scale_(this->config->thin_walls_min_width.get_abs_value(this->ext_perimeter_flow.nozzle_diameter));
                         
                         ExPolygons no_thin_zone = offset_ex(next_onion, (float)(ext_perimeter_width / 2), jtSquare);
                         // medial axis requires non-overlapping geometry
@@ -297,8 +297,9 @@ void PerimeterGenerator::process()
                                     if (thin[0].area() > min_width*(ext_perimeter_width + ext_perimeter_spacing2)) {
                                         bound.remove_point_too_near(SCALED_RESOLUTION);
                                         // the maximum thickness of our thin wall area is equal to the minimum thickness of a single loop
-                                        thin[0].medial_axis(bound, ext_perimeter_width + ext_perimeter_spacing2, min_width,
+                                        Slic3r::MedialAxis ma(thin[0], bound, ext_perimeter_width + ext_perimeter_spacing2, min_width, this->layer_height);
-                                            &thin_walls, this->layer_height);
+                                        ma.nozzle_diameter = (coord_t)scale_(this->ext_perimeter_flow.nozzle_diameter);
+                                        ma.build(&thin_walls);
                                         thin_zones_extruded.emplace_back(thin[0]);
                                     }
                                     break;

src/libslic3r/PrintConfig.cpp

@@ -2346,7 +2346,7 @@ void PrintConfigDef::init_fff_params()
     def->default_value = new ConfigOptionInts { 200 };
     
     def = this->add("thin_walls", coBool);
-    def->label = L("Detect thin walls");
+    def->label = L("");
     def->category = L("Layers and Perimeters");
     def->tooltip = L("Detect single-width walls (parts where two extrusions don't fit and we need "
                    "to collapse them into a single trace).");
@@ -2354,6 +2354,15 @@ void PrintConfigDef::init_fff_params()
     def->mode = comAdvanced;
     def->default_value = new ConfigOptionBool(true);
 
+    def = this->add("thin_walls_min_width", coFloatOrPercent);
+    def->label = L("min width");
+    def->category = L("Layers and Perimeters");
+    def->tooltip = L("Minimum width for the extrusion to be extruded (widths lower than the nozzle diameter will be over-extruded at the nozzle diameter). Can be percent of the nozzle size.");
+    def->cli = "thin-walls-min-width=s";
+    def->mode = comExpert;
+    def->min = 0;
+    def->default_value = new ConfigOptionFloatOrPercent(33,true);
+
     def = this->add("threads", coInt);
     def->label = L("Threads");
     def->tooltip = L("Threads are used to parallelize long-running tasks. Optimal threads number "

src/libslic3r/PrintConfig.hpp

@@ -519,6 +519,7 @@ public:
     ConfigOptionFloatOrPercent      solid_infill_speed;
     // Detect thin walls.
     ConfigOptionBool                thin_walls;
+    ConfigOptionFloatOrPercent      thin_walls_min_width;
     ConfigOptionFloatOrPercent      top_infill_extrusion_width;
     ConfigOptionInt                 top_solid_layers;
     ConfigOptionFloatOrPercent      top_solid_infill_speed;
@@ -574,6 +575,7 @@ protected:
         OPT_PTR(solid_infill_every_layers);
         OPT_PTR(solid_infill_speed);
         OPT_PTR(thin_walls);
+        OPT_PTR(thin_walls_min_width);
         OPT_PTR(top_infill_extrusion_width);
         OPT_PTR(top_solid_infill_speed);
         OPT_PTR(top_solid_layers);

src/libslic3r/PrintObject.cpp

@@ -462,6 +462,7 @@ bool PrintObject::invalidate_state_by_config_options(const std::vector<t_config_
             || opt_key == "perimeter_extrusion_width"
             || opt_key == "infill_overlap"
             || opt_key == "thin_walls"
+            || opt_key == "thin_walls_min_width"
             || opt_key == "external_perimeters_first"
             || opt_key == "perimeter_loop"
             || opt_key == "perimeter_loop_seam"

src/slic3r/GUI/Preset.cpp

@@ -353,6 +353,7 @@ const std::vector<std::string>& Preset::print_options()
         , "infill_not_connected"
         , "first_layer_infill_speed"
         , "label_printed_objects"
+        , "thin_walls_min_width"
     };
     return s_opts;
 }

src/slic3r/GUI/Tab.cpp

@@ -923,7 +923,10 @@ 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_walls");
+        line = { _(L("Thin walls")), "" };
+        line.append_option(optgroup->get_option("thin_walls"));
+        line.append_option(optgroup->get_option("thin_walls_min_width"));
+        optgroup->append_line(line);
 		optgroup->append_single_option_line("overhangs");
         line = { _(L("Avoid unsupported perimeters")), "" };
         line.append_option(optgroup->get_option("no_perimeter_unsupported"));
@@ -1322,10 +1325,11 @@ void TabPrint::update()
 
     bool have_perimeters = m_config->opt_int("perimeters") > 0;
     for (auto el : { "extra_perimeters", "only_one_perimeter_top", "ensure_vertical_shell_thickness", "thin_walls", "overhangs",
-        "seam_position", "external_perimeters_first", "external_perimeter_extrusion_width",
+        "seam_position", "external_perimeters_first", "external_perimeter_extrusion_width", "thin_walls_min_width",
         "perimeter_speed", "small_perimeter_speed", "external_perimeter_speed", "perimeter_loop", "perimeter_loop_seam" })
         get_field(el)->toggle(have_perimeters);
 
+    get_field("thin_walls_min_width")->toggle(m_config->opt_bool("thin_walls"));
     get_field("perimeter_loop_seam")->toggle(m_config->opt_bool("perimeter_loop"));
 
     bool have_no_perimeter_unsupported = have_perimeters && m_config->opt_bool("no_perimeter_unsupported");