Add configurable short wall/perimeter cleaning for Arachne (#2790)

* add feature to add configurable value to clean/remove short un-closed walls/perimeters, to improve print times and reduce stringing (and generally lead to a cleaner print).

* fixes to short wall removal, which no longer affects bottom or top surfaces. allowed adjusting Top-surface threshold (renamed from One wall threshold for clarity) when short wall removal value is configured above default of 0.5.

* small fix for toggle_line for min_width_top_surface, to only be visible if min_length_factor > 0.5 and arachne is enabled.

* Use copy of input_params

* revert `One wall threshold"` string change

---------

Co-authored-by: SoftFever <softfeverever@gmail.com>

src/libslic3r/Arachne/WallToolPaths.cpp

@@ -31,6 +31,11 @@ WallToolPathsParams make_paths_params(const int layer_id, const PrintObjectConfi
         if (const auto &min_feature_size_opt = print_object_config.min_feature_size)
             input_params.min_feature_size = min_feature_size_opt.value * 0.01 * min_nozzle_diameter;
 
+        if (const auto &min_wall_length_factor_opt = print_object_config.min_length_factor)
+            input_params.min_length_factor = min_wall_length_factor_opt.value;
+        else
+            input_params.min_length_factor = 0.5f;
+
         if (layer_id == 0) {
             if (const auto &initial_layer_min_bead_width_opt = print_object_config.initial_layer_min_bead_width)
                 input_params.min_bead_width = initial_layer_min_bead_width_opt.value * 0.01 * min_nozzle_diameter;
@@ -47,6 +52,8 @@ WallToolPathsParams make_paths_params(const int layer_id, const PrintObjectConfi
 
         input_params.wall_transition_angle   = print_object_config.wall_transition_angle.value;
         input_params.wall_distribution_count = print_object_config.wall_distribution_count.value;
+
+        input_params.is_top_or_bottom_layer = false; // Set to default value
     }
 
     return input_params;
@@ -671,7 +678,8 @@ void WallToolPaths::removeSmallLines(std::vector<VariableWidthLines> &toolpaths)
             coord_t        min_width = std::numeric_limits<coord_t>::max();
             for (const ExtrusionJunction &j : line)
                 min_width = std::min(min_width, j.w);
-            if (line.is_odd && !line.is_closed && shorterThan(line, min_width / 2)) { // remove line
+            // Only use min_length_factor for non-topmost, to prevent top gaps. Otherwise use default value.
+            if (line.is_odd && !line.is_closed && shorterThan(line, m_params.is_top_or_bottom_layer ? (min_width / 2) : (min_width * m_params.min_length_factor))) { // remove line
                 line = std::move(inset.back());
                 inset.erase(--inset.end());
                 line_idx--; // reconsider the current position

src/libslic3r/Arachne/WallToolPaths.hpp

@@ -25,10 +25,12 @@ class WallToolPathsParams
 public:
     float   min_bead_width;
     float   min_feature_size;
+    float   min_length_factor;
     float   wall_transition_length;
     float   wall_transition_angle;
     float   wall_transition_filter_deviation;
     int     wall_distribution_count;
+    bool    is_top_or_bottom_layer;
 };
 
 WallToolPathsParams make_paths_params(const int layer_id, const PrintObjectConfig &print_object_config, const PrintConfig &print_config);
@@ -109,7 +111,7 @@ protected:
     /*!
      * Remove polylines shorter than half the smallest line width along that polyline.
      */
-    static void removeSmallLines(std::vector<VariableWidthLines> &toolpaths);
+    void removeSmallLines(std::vector<VariableWidthLines> &toolpaths);
 
     /*!
      * Simplifies the variable-width toolpaths by calling the simplify on every line in the toolpath using the provided

src/libslic3r/PerimeterGenerator.cpp

@@ -1941,10 +1941,15 @@ void PerimeterGenerator::process_arachne()
         int        loop_number = this->config->wall_loops + surface.extra_perimeters - 1; // 0-indexed loops
         if (this->config->alternate_extra_wall && this->layer_id % 2 == 1 && !m_spiral_vase) // add alternating extra wall
             loop_number++;
-        if (this->layer_id == 0 && this->config->only_one_wall_first_layer)
+
+        // Set the bottommost layer to be one wall
+        const bool is_bottom_layer = (this->layer_id == 0) ? true : false;
+        if (is_bottom_layer && this->config->only_one_wall_first_layer)
             loop_number = 0;
+
         // Orca: set the topmost layer to be one wall according to the config
-        if (loop_number > 0 && config->only_one_wall_top && this->upper_slices == nullptr)
+        const bool is_topmost_layer = (this->upper_slices == nullptr) ? true : false;
+        if (is_topmost_layer && loop_number > 0 && config->only_one_wall_top)
             loop_number = 0;
         // Orca: properly adjust offset for the outer wall if precise_outer_wall is enabled.
         ExPolygons last = offset_ex(surface.expolygon.simplify_p(surface_simplify_resolution),
@@ -1952,6 +1957,9 @@ void PerimeterGenerator::process_arachne()
                                                  : -float(ext_perimeter_width / 2. - ext_perimeter_spacing / 2.));
         
         Arachne::WallToolPathsParams input_params = Arachne::make_paths_params(this->layer_id, *object_config, *print_config);
+        // Set params is_top_or_bottom_layer for adjusting short-wall removal sensitivity.
+        input_params.is_top_or_bottom_layer = (is_bottom_layer || is_topmost_layer) ? true : false;
+
         coord_t wall_0_inset = 0;
         if (config->precise_outer_wall)
            wall_0_inset = -coord_t(ext_perimeter_width / 2 - ext_perimeter_spacing / 2);
@@ -1959,18 +1967,33 @@ void PerimeterGenerator::process_arachne()
         std::vector<Arachne::VariableWidthLines> out_shell;
         ExPolygons top_fills;
         ExPolygons fill_clip;
-        if (loop_number > 0 && config->only_one_wall_top && !surface.is_bridge() && this->upper_slices != nullptr) {
-            // Check if current layer has surfaces that are not covered by upper layer (i.e., top surfaces)
-            ExPolygons non_top_polygons;
-            this->split_top_surfaces(last, top_fills, non_top_polygons, fill_clip);
 
-            if (top_fills.empty()) {
+        // Check if we're on a top surface, and make adjustments where needed
+        if (!surface.is_bridge() && !is_topmost_layer) {
+            ExPolygons non_top_polygons;
+            // Temporary storage, in the event all we need to do is set is_top_or_bottom_layer
+            ExPolygons top_fills_tmp;
+            ExPolygons fill_clip_tmp;
+            // Check if current layer has surfaces that are not covered by upper layer (i.e., top surfaces)
+            this->split_top_surfaces(last, top_fills_tmp, non_top_polygons, fill_clip_tmp);
+
+            if (top_fills_tmp.empty()) {
                 // No top surfaces, no special handling needed
             } else {
+                // Use single-wall on top-surfaces if configured
+                if (loop_number > 0 && config->only_one_wall_top) {
+                    // Adjust arachne input params to prevent removal of larger short walls, which could lead to gaps
+                    Arachne::WallToolPathsParams input_params_tmp = input_params;
+                    input_params_tmp.is_top_or_bottom_layer = true;
+                
+                    // Swap in the temporary storage
+                    top_fills.swap(top_fills_tmp);
+                    fill_clip.swap(fill_clip_tmp);
+                    
                     // First we slice the outer shell
                     Polygons last_p = to_polygons(last);
                     Arachne::WallToolPaths wallToolPaths(last_p, bead_width_0, perimeter_spacing, coord_t(1),
-                                                     wall_0_inset, layer_height, input_params);
+                                                        wall_0_inset, layer_height, input_params_tmp);
                     out_shell = wallToolPaths.getToolPaths();
                     // Make sure infill not overlap with wall
                     top_fills = intersection_ex(top_fills, wallToolPaths.getInnerContour());
@@ -1985,6 +2008,7 @@ void PerimeterGenerator::process_arachne()
                     }
                 }
             }
+        }
 
         Polygons last_p = to_polygons(last);
 

src/libslic3r/Preset.cpp

@@ -804,7 +804,7 @@ static std::vector<std::string> s_Preset_print_options {
      "initial_layer_infill_speed", "only_one_wall_top", 
      "timelapse_type",
      "wall_generator", "wall_transition_length", "wall_transition_filter_deviation", "wall_transition_angle",
-     "wall_distribution_count", "min_feature_size", "min_bead_width", "post_process",
+     "wall_distribution_count", "min_feature_size", "min_bead_width", "post_process", "min_length_factor",
      "small_perimeter_speed", "small_perimeter_threshold","bridge_angle", "filter_out_gap_fill", "travel_acceleration","inner_wall_acceleration", "min_width_top_surface",
      "default_jerk", "outer_wall_jerk", "inner_wall_jerk", "infill_jerk", "top_surface_jerk", "initial_layer_jerk","travel_jerk",
      "top_solid_infill_flow_ratio","bottom_solid_infill_flow_ratio","only_one_wall_first_layer", "print_flow_ratio", "seam_gap",

src/libslic3r/PrintConfig.cpp

@@ -4540,6 +4540,20 @@ def = this->add("filament_loading_speed", coFloats);
     def->min = 0;
     def->set_default_value(new ConfigOptionPercent(25));
 
+    def = this->add("min_length_factor", coFloat);
+    def->label = L("Minimum wall length");
+    def->category = L("Quality");
+    def->tooltip = L("Adjust this value to prevent short, unclosed walls from being printed, which could increase print time. "
+    "Higher values remove more and longer walls.\n\n"
+    "NOTE: Bottom and top surfaces will not be affected by this value to prevent visual gaps on the ouside of the model. "
+    "Adjust 'One wall threshold' in the Advanced settings below to adjust the sensitivity of what is considered a top-surface. "
+    "'One wall threshold' is only visibile if this setting is set above the default value of 0.5, or if single-wall top surfaces is enabled.");
+    def->sidetext = L("");
+    def->mode = comAdvanced;
+    def->min = 0.0;
+    def->max = 25.0;
+    def->set_default_value(new ConfigOptionFloat(0.5));
+
     def = this->add("initial_layer_min_bead_width", coPercent);
     def->label = L("First layer minimum wall width");
     def->category = L("Quality");

src/libslic3r/PrintConfig.hpp

@@ -784,6 +784,7 @@ PRINT_CONFIG_CLASS_DEFINE(
     ((ConfigOptionPercent,            tree_support_top_rate))
     ((ConfigOptionFloat,              tree_support_branch_diameter_organic))
     ((ConfigOptionFloat,              tree_support_branch_angle_organic))
+    ((ConfigOptionFloat,              min_length_factor))
 
     // Move all acceleration and jerk settings to object
     ((ConfigOptionFloat,              default_acceleration))

src/libslic3r/PrintObject.cpp

@@ -1127,6 +1127,7 @@ bool PrintObject::invalidate_state_by_config_options(
             || opt_key == "wall_transition_angle"
             || opt_key == "wall_distribution_count"
             || opt_key == "min_feature_size"
+            || opt_key == "min_length_factor"
             || opt_key == "min_bead_width") {
             steps.emplace_back(posSlice);
         } else if (

src/slic3r/GUI/ConfigManipulation.cpp

@@ -695,7 +695,7 @@ void ConfigManipulation::toggle_print_fff_options(DynamicPrintConfig *config, co
     
     bool have_arachne = config->opt_enum<PerimeterGeneratorType>("wall_generator") == PerimeterGeneratorType::Arachne;
     for (auto el : { "wall_transition_length", "wall_transition_filter_deviation", "wall_transition_angle",
-        "min_feature_size", "min_bead_width", "wall_distribution_count", "initial_layer_min_bead_width"})
+        "min_feature_size", "min_length_factor", "min_bead_width", "wall_distribution_count", "initial_layer_min_bead_width"})
         toggle_line(el, have_arachne);
     toggle_field("detect_thin_wall", !have_arachne);
     
@@ -712,7 +712,7 @@ void ConfigManipulation::toggle_print_fff_options(DynamicPrintConfig *config, co
     toggle_line("make_overhang_printable_angle", have_make_overhang_printable);
     toggle_line("make_overhang_printable_hole_size", have_make_overhang_printable);
     
-    toggle_line("min_width_top_surface",config->opt_bool("only_one_wall_top"));
+    toggle_line("min_width_top_surface", config->opt_bool("only_one_wall_top") || ((config->opt_float("min_length_factor") > 0.5f) && have_arachne)); // 0.5 is default value
 
     for (auto el : { "hole_to_polyhole_threshold", "hole_to_polyhole_twisted" })
         toggle_line(el, config->opt_bool("hole_to_polyhole"));

src/slic3r/GUI/Tab.cpp

@@ -1957,6 +1957,7 @@ void TabPrint::build()
         optgroup->append_single_option_line("initial_layer_min_bead_width");
         optgroup->append_single_option_line("min_bead_width");
         optgroup->append_single_option_line("min_feature_size");
+        optgroup->append_single_option_line("min_length_factor");
 
         optgroup = page->new_optgroup(L("Walls and surfaces"), L"param_advanced");
         optgroup->append_single_option_line("wall_sequence");
@@ -1964,8 +1965,8 @@ void TabPrint::build()
         optgroup->append_single_option_line("print_flow_ratio");
         optgroup->append_single_option_line("top_solid_infill_flow_ratio");
         optgroup->append_single_option_line("bottom_solid_infill_flow_ratio");
-        optgroup->append_single_option_line("only_one_wall_top");
         optgroup->append_single_option_line("min_width_top_surface");
+        optgroup->append_single_option_line("only_one_wall_top");
         optgroup->append_single_option_line("only_one_wall_first_layer");
         optgroup->append_single_option_line("reduce_crossing_wall");
         optgroup->append_single_option_line("max_travel_detour_distance");