ENH: improve auto-arranging objects with tree support

We decide to set brim width of all objects to MAX_BRANCH_RADIUS_FIRST_LAYER if there is an object with tree support after discussion.

Jira: MAK-2009
Change-Id: I4c4940800632c433235966b01c44ac910e33a51c

src/libslic3r/Arrange.cpp

@@ -102,8 +102,17 @@ void update_selected_items_inflation(ArrangePolygons& selected, const DynamicPri
     // do not inflate brim_width. Objects are allowed to have overlapped brim.
     Points      bedpts = get_shrink_bedpts(print_cfg, params);
     BoundingBox bedbb = Polygon(bedpts).bounding_box();
+    double brim_max = 0;
+    bool plate_has_tree_support = false;
     std::for_each(selected.begin(), selected.end(), [&](ArrangePolygon& ap) {
-        ap.inflation = params.min_obj_distance == 0 ? scaled(ap.brim_width) : params.min_obj_distance / 2;
+        brim_max = std::max(brim_max, ap.brim_width);
+        if (ap.has_tree_support) plate_has_tree_support = true; });
+    std::for_each(selected.begin(), selected.end(), [&](ArrangePolygon& ap) {
+        // 1. if user input a distance, use it
+        // 2. if there is an object with tree support, all objects use the max tree branch radius (brim_max=branch diameter)
+        // 3. otherwise, use each object's own brim width
+        ap.inflation = params.min_obj_distance != 0 ? params.min_obj_distance / 2 :
+            plate_has_tree_support ? scaled(brim_max / 2) : scaled(ap.brim_width);
         BoundingBox apbb = ap.poly.contour.bounding_box();
         auto        diffx = bedbb.size().x() - apbb.size().x() - 5;
         auto        diffy = bedbb.size().y() - apbb.size().y() - 5;

src/libslic3r/Arrange.hpp

@@ -53,7 +53,8 @@ struct ArrangePolygon {
     int       locked_plate{ -1 };
     bool      is_virt_object{ false };
     bool      is_extrusion_cali_object{ false };
-    bool      is_wipe_tower{false};
+    bool      is_wipe_tower{ false };
+    bool      has_tree_support{false};
     //BBS: add row/col for sudoku-style layout
     int       row{0};
     int       col{0};

src/libslic3r/ModelArrange.cpp

@@ -159,7 +159,8 @@ ArrangePolygon get_instance_arrange_poly(ModelInstance* instance, const Slic3r::
     if (enable_support && (support_type == stNormalAuto || support_type == stNormal))
         ap.brim_width = 6.0;
     else if (enable_support) {
-        ap.brim_width = 22.0;
+        ap.brim_width = 24.0; // 2*MAX_BRANCH_RADIUS_FIRST_LAYER
+        ap.has_tree_support = true;
     }
     
     ap.height = obj->bounding_box().size().z();

src/libslic3r/TreeSupport.cpp

@@ -2205,7 +2205,7 @@ void TreeSupport::draw_circles(const std::vector<std::vector<Node*>>& contact_no
                             }
                         }
                         if (layer_nr == 0 && m_raft_layers == 0) {
-                            double brim_width = tree_brim_width > 0 ? tree_brim_width : layers_to_top * layer_height / (scale * branch_radius) * 0.5;
+                            double brim_width = tree_brim_width > 0 ? tree_brim_width : std::max(0.0, std::min(node.radius + node.dist_mm_to_top / (scale * branch_radius) * 0.5, MAX_BRANCH_RADIUS_FIRST_LAYER) - node.radius);
                             circle = offset(circle, scale_(brim_width))[0];
                         }
                         area.emplace_back(ExPolygon(circle));

src/libslic3r/TreeSupport.hpp

@@ -419,6 +419,7 @@ private:
     std::vector<std::vector<MinimumSpanningTree>> m_spanning_trees;
     std::vector< std::unordered_map<Line, bool, LineHash>> m_mst_line_x_layer_contour_caches;
     coordf_t MAX_BRANCH_RADIUS = 10.0;
+    coordf_t MAX_BRANCH_RADIUS_FIRST_LAYER = 12.0;
     coordf_t MIN_BRANCH_RADIUS = 0.5;
     float tree_support_branch_diameter_angle = 5.0;
     bool  is_strong = false;