ENH: avoid overhang area when set the seam position

Signed-off-by: qing.zhang <qing.zhang@bambulab.com>
Change-Id: I58eb8c091b68b8c64f44d21db88d2f9155e42e42

src/libslic3r/GCode/SeamPlacer.cpp

@@ -697,8 +697,8 @@ struct SeamComparator
         }
 
         // the penalites are kept close to range [0-1.x] however, it should not be relied upon
-        float penalty_a = a.overhang + a.visibility + angle_importance * compute_angle_penalty(a.local_ccw_angle) + distance_penalty_a;
+        float penalty_a = a.overhang + a.visibility + a.extend_overhang + angle_importance * compute_angle_penalty(a.local_ccw_angle) + distance_penalty_a;
-        float penalty_b = b.overhang + b.visibility + angle_importance * compute_angle_penalty(b.local_ccw_angle) + distance_penalty_b;
+        float penalty_b = b.overhang + b.visibility + b.extend_overhang + angle_importance * compute_angle_penalty(b.local_ccw_angle) + distance_penalty_b;
 
         return penalty_a < penalty_b;
     }
@@ -731,8 +731,8 @@ struct SeamComparator
 
         if (setup == SeamPosition::spRear) { return a.position.y() + SeamPlacer::seam_align_score_tolerance * 5.0f > b.position.y(); }
 
-        float penalty_a = a.overhang + a.visibility + angle_importance * compute_angle_penalty(a.local_ccw_angle);
+        float penalty_a = a.overhang + a.extend_overhang + a.visibility + angle_importance * compute_angle_penalty(a.local_ccw_angle);
-        float penalty_b = b.overhang + b.visibility + angle_importance * compute_angle_penalty(b.local_ccw_angle);
+        float penalty_b = b.overhang + b.extend_overhang + b.visibility + angle_importance * compute_angle_penalty(b.local_ccw_angle);
 
         return penalty_a <= penalty_b || penalty_a - penalty_b < SeamPlacer::seam_align_score_tolerance;
     }
@@ -968,12 +968,50 @@ void SeamPlacer::calculate_overhangs_and_layer_embedding(const PrintObject *po)
             bool                                should_compute_layer_embedding = regions_with_perimeter > 1;
             std::unique_ptr<PerimeterDistancer> current_layer_distancer        = std::make_unique<PerimeterDistancer>(po->layers()[layer_idx]);
 
-            for (SeamCandidate &perimeter_point : layers[layer_idx].points) {
+            int points_size = layers[layer_idx].points.size();
+            for (size_t i = 0; i < points_size; i++) {
+                SeamCandidate &perimeter_point = layers[layer_idx].points[i];
                 Vec2f point = Vec2f{perimeter_point.position.head<2>()};
                 if (prev_layer_distancer.get() != nullptr) {
                     perimeter_point.overhang = prev_layer_distancer->distance_from_perimeter(point) + 0.6f * perimeter_point.perimeter.flow_width -
                                                tan(SeamPlacer::overhang_angle_threshold) * po->layers()[layer_idx]->height;
                     perimeter_point.overhang = perimeter_point.overhang < 0.0f ? 0.0f : perimeter_point.overhang;
+                    if (perimeter_point.overhang > 0.0f) {
+                        //BBS. extend overhang range
+                        float  dist  = 0.0f;
+                        size_t idx   = i;
+                        size_t start_index = layers[layer_idx].points[i].perimeter.start_index;
+                        size_t end_index = layers[layer_idx].points[i].perimeter.end_index;
+                        float  lensLimit   = 3.0f;
+                        bool   flage = true;
+                        layers[layer_idx].points[i].extend_overhang += gauss(0.0f, 0.0f, 1.0f, 0.005f);
+
+                        while (idx != i || flage) {
+                            flage      = false;
+                            int prev   = idx;
+                            idx        = idx == start_index ? end_index - 1 : idx - 1;
+                            dist += sqrt((layers[layer_idx].points[idx].position.head<2>() - layers[layer_idx].points[prev].position.head<2>()).squaredNorm());
+                            if (dist > lensLimit)
+                                break;
+                            else
+                                layers[layer_idx].points[idx].extend_overhang += gauss(dist, 0.0f, 1.0f, 0.005f);
+                        }
+
+                        idx   = i;
+                        dist  = 0.0f;
+                        flage = true;
+
+                        while (idx != i || flage) {
+                            flage      = false;
+                            int prev   = idx;
+                            idx        = idx == end_index - 1 ? start_index : idx + 1;
+                            dist += sqrt((layers[layer_idx].points[idx].position.head<2>() - layers[layer_idx].points[prev].position.head<2>()).squaredNorm());
+                            if (dist > lensLimit)
+                                break;
+                            else
+                                layers[layer_idx].points[idx].extend_overhang += gauss(dist, 0.0f, 1.0f, 0.005f);
+                        }
+                    }
                 }
 
                 if (should_compute_layer_embedding) { // search for embedded perimeter points (points hidden inside the print ,e.g. multimaterial join, best position for seam)

src/libslic3r/GCode/SeamPlacer.hpp

@@ -76,6 +76,7 @@ struct SeamCandidate
     Perimeter &perimeter;
     float      visibility;
     float      overhang;
+    float      extend_overhang=0.0f;
     // distance inside the merged layer regions, for detecting perimeter points which are hidden indside the print (e.g. multimaterial join)
     // Negative sign means inside the print, comes from EdgeGrid structure
     float                    embedded_distance;