Configure skirt start point

src/libslic3r/GCode.cpp

@@ -3425,6 +3425,33 @@ namespace Skirt {
         return skirt_loops_per_extruder_out;
     }
 
+    static Point find_start_point(ExtrusionLoop& loop, float start_angle) {
+        coord_t min_x = std::numeric_limits<coord_t>::max();
+        coord_t max_x = std::numeric_limits<coord_t>::min();
+        coord_t min_y = min_x;
+        coord_t max_y = max_x;
+
+        Points pts;
+        loop.collect_points(pts);
+        for (Point pt: pts) {
+            if (pt.x() < min_x)
+                min_x = pt.x();
+            else if (pt.x() > max_x)
+                max_x = pt.x();
+            if (pt.y() < min_y)
+                min_y = pt.y();
+            else if (pt.y() > max_y)
+                max_y = pt.y();
+        }
+
+        Point center((min_x + max_x)/2., (min_y + max_y)/2.);
+        double r       = center.distance_to(Point(min_x, min_y));
+        double deg     = start_angle * PI / 180;
+        double shift_x = r * std::cos(deg);
+        double shift_y = r * std::sin(deg);
+        return Point(center.x()+shift_x, center.y() + shift_y);
+    }
+
 } // namespace Skirt
 
 // Orca: Klipper can't parse object names with spaces and other spetical characters
@@ -3995,6 +4022,11 @@ LayerResult GCode::process_layer(
                     path.height = layer_skirt_flow.height();
                     path.mm3_per_mm = mm3_per_mm;
                 }
+
+                //set skirt start point location
+                if (first_layer && i==loops.first)
+                    this->set_last_pos(Skirt::find_start_point(loop, layer.object()->config().skirt_start_angle));
+
                 //FIXME using the support_speed of the 1st object printed.
                 gcode += this->extrude_loop(loop, "skirt", m_config.support_speed.value);
             }

src/libslic3r/Preset.cpp

@@ -774,7 +774,7 @@ static std::vector<std::string> s_Preset_print_options {
     "inner_wall_speed", "outer_wall_speed", "sparse_infill_speed", "internal_solid_infill_speed",
     "top_surface_speed", "support_speed", "support_object_xy_distance", "support_interface_speed",
     "bridge_speed", "internal_bridge_speed", "gap_infill_speed", "travel_speed", "travel_speed_z", "initial_layer_speed",
-    "outer_wall_acceleration", "initial_layer_acceleration", "top_surface_acceleration", "default_acceleration", "skirt_loops", "skirt_speed","min_skirt_length", "skirt_distance", "skirt_height", "draft_shield",
+    "outer_wall_acceleration", "initial_layer_acceleration", "top_surface_acceleration", "default_acceleration", "skirt_loops", "skirt_speed","min_skirt_length", "skirt_distance", "skirt_start_angle", "skirt_height", "draft_shield",
     "brim_width", "brim_object_gap", "brim_type", "brim_ears_max_angle", "brim_ears_detection_length", "enable_support", "support_type", "support_threshold_angle", "enforce_support_layers",
     "raft_layers", "raft_first_layer_density", "raft_first_layer_expansion", "raft_contact_distance", "raft_expansion",
     "support_base_pattern", "support_base_pattern_spacing", "support_expansion", "support_style",

src/libslic3r/Print.cpp

@@ -225,6 +225,7 @@ bool Print::invalidate_state_by_config_options(const ConfigOptionResolver & /* n
             || opt_key == "min_skirt_length"
             || opt_key == "draft_shield"
             || opt_key == "skirt_distance"
+            || opt_key == "skirt_start_angle"
             || opt_key == "ooze_prevention"
             || opt_key == "wipe_tower_x"
             || opt_key == "wipe_tower_y"

src/libslic3r/PrintConfig.cpp

@@ -3992,6 +3992,15 @@ void PrintConfigDef::init_fff_params()
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionFloat(2));
 
+    def = this->add("skirt_start_angle", coFloat);
+    def->label = L("Skirt start point");
+    def->tooltip = L("Angle from the object center to skirt start point. Zero is the most right position, counter clockwise is positive angle.");
+    def->sidetext = L("°");
+    def->min = -180;
+    def->max = 180;
+    def->mode = comAdvanced;
+    def->set_default_value(new ConfigOptionFloat(-135));
+
     def = this->add("skirt_height", coInt);
     def->label = L("Skirt height");
     //def->label = "Skirt height";

src/libslic3r/PrintConfig.hpp

@@ -1220,6 +1220,7 @@ PRINT_CONFIG_CLASS_DERIVED_DEFINE(
     ((ConfigOptionFloats,             retraction_minimum_travel))
     ((ConfigOptionBools,              retract_when_changing_layer))
     ((ConfigOptionFloat,              skirt_distance))
+    ((ConfigOptionFloat,              skirt_start_angle))
     ((ConfigOptionInt,                skirt_height))
     ((ConfigOptionInt,                skirt_loops))
     ((ConfigOptionFloat,              skirt_speed))