From 6df07fb6b9d82cd1e101b197bac53c5cb8a4eb93 Mon Sep 17 00:00:00 2001
From: "yifan.wu" <yifan.wu@bambulab.com>
Date: Wed, 20 Jul 2022 21:33:15 +0800
Subject: [PATCH] ENH: optimize support top intface fill direction

Optimize support top interface fill direction for bridge.
The direction is set orthogonal to the biggest bridges's infill
direction.
Currently, it only works when thick bridge is off.

Signed-off-by: yifan.wu <yifan.wu@bambulab.com>
Change-Id: I7bd894ae6f5ae24bc597c609e27a16b6d45a9797
---
 src/libslic3r/SupportMaterial.cpp | 50 +++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/src/libslic3r/SupportMaterial.cpp b/src/libslic3r/SupportMaterial.cpp
index a0c4085aec0..1abedc40756 100644
--- a/src/libslic3r/SupportMaterial.cpp
+++ b/src/libslic3r/SupportMaterial.cpp
@@ -4642,6 +4642,40 @@ void PrintObjectSupportMaterial::generate_toolpaths(
             }
 #endif
 
+            // Calculate top interface angle
+            float angle_of_biggest_bridge = -1.f;
+            do
+            {
+                // Currently only works when thick_bridges is off
+                if (m_object->config().thick_bridges)
+                    break;
+
+                coordf_t object_layer_bottom_z = support_layer.print_z + m_slicing_params.gap_support_object;
+                const Layer* object_layer = m_object->get_layer_at_bottomz(object_layer_bottom_z, 10.0 * EPSILON);
+                if (object_layer == nullptr)
+                    break;
+
+                if (object_layer != nullptr) {
+                    float biggest_bridge_area = 0.f;
+                    const Polygons& top_contact_polys = top_contact_layer.polygons_to_extrude();
+                    for (auto layerm : object_layer->regions()) {
+                        for (auto bridge_surface : layerm->fill_surfaces.filter_by_type(stBottomBridge)) {
+                            float bs_area = bridge_surface->area();
+                            if (bs_area <= biggest_bridge_area || bridge_surface->bridge_angle < 0.f)
+                                continue;
+
+                            angle_of_biggest_bridge = bridge_surface->bridge_angle;
+                            biggest_bridge_area = bs_area;
+                        }
+                    }
+                }
+            } while (0);
+
+            auto calc_included_angle_degree = [](int degree_a, int degree_b) {
+                int iad = std::abs(degree_b - degree_a);
+                return std::min(iad, 180 - iad);
+            };
+
             // Top and bottom contacts, interface layers.
             for (size_t i = 0; i < 3; ++ i) {
                 MyLayerExtruded &layer_ex = (i == 0) ? top_contact_layer : (i == 1 ? bottom_contact_layer : interface_layer);
@@ -4664,6 +4698,22 @@ void PrintObjectSupportMaterial::generate_toolpaths(
                         // Use interface angle for the interface layers.
                         m_support_params.interface_angle + interface_angle_delta;
 
+                // BBS
+                bool can_adjust_top_interface_angle = (m_object_config->support_interface_top_layers.value > 1 && &layer_ex == &top_contact_layer);
+                if (can_adjust_top_interface_angle && angle_of_biggest_bridge >= 0.f) {
+                    int bridge_degree = (int)Geometry::rad2deg(angle_of_biggest_bridge);
+                    int support_intf_degree = (int)Geometry::rad2deg(filler_interface->angle);
+                    int max_included_degree = 0;
+                    int step = 90;
+                    for (int add_on_degree = 0; add_on_degree < 180; add_on_degree += step) {
+                        int degree_to_try = support_intf_degree + add_on_degree;
+                        int included_degree = calc_included_angle_degree(bridge_degree, degree_to_try);
+                        if (included_degree > max_included_degree) {
+                            max_included_degree = included_degree;
+                            filler_interface->angle = Geometry::deg2rad((float)degree_to_try);
+                        }
+                    }
+                }
                 double density = interface_as_base ? m_support_params.support_density : m_support_params.interface_density;
                 filler_interface->spacing = interface_as_base ? m_support_params.support_material_flow.spacing() : m_support_params.support_material_interface_flow.spacing();
                 filler_interface->link_max_length = coord_t(scale_(filler_interface->spacing * link_max_length_factor / density));