Optimize painting using single triangle brush.

Especially on the detail models, painting using the single triangle brush is noticeably faster.

src/libslic3r/TriangleSelector.cpp

@@ -583,11 +583,17 @@ void TriangleSelector::bucket_fill_select_triangles(const Vec3f &hit, int facet_
 
     assert(!m_triangles[start_facet_idx].is_split());
     TriangleStateType start_facet_state = m_triangles[start_facet_idx].get_state();
-    this->seed_fill_unselect_all_triangles();
 
     if (propagate == BucketFillPropagate::NO) {
+        if (m_triangle_selected_by_seed_fill != -1)
+            this->seed_fill_unselect_triangle(m_triangle_selected_by_seed_fill);
+
         m_triangles[start_facet_idx].select_by_seed_fill();
+        m_triangle_selected_by_seed_fill = start_facet_idx;
         return;
+    } else {
+        m_triangle_selected_by_seed_fill = -1;
+        this->seed_fill_unselect_all_triangles();
     }
 
     const float facet_angle_limit = std::cos(Geometry::deg2rad(bucket_fill_angle)) - EPSILON;
@@ -1286,10 +1292,10 @@ void TriangleSelector::undivide_triangle(int facet_idx)
     }
 }
 
-void TriangleSelector::remove_useless_children(int facet_idx)
+// Returns true when some triangle during recursive descending was removed (undivided).
-{
+bool TriangleSelector::remove_useless_children(int facet_idx) {
     // Check that all children are leafs of the same type. If not, try to
-    // make them (recursive call). Remove them if sucessful.
+    // make them (recursive call). Remove them if successful.
 
     assert(facet_idx < int(m_triangles.size()) && m_triangles[facet_idx].valid());
     Triangle &tr = m_triangles[facet_idx];
@@ -1297,31 +1303,32 @@ void TriangleSelector::remove_useless_children(int facet_idx)
     if (!tr.is_split()) {
         // This is a leaf, there nothing to do. This can happen during the
         // first (non-recursive call). Shouldn't otherwise.
-        return;
+        return false;
     }
 
     // Call this for all non-leaf children.
+    bool children_removed = false;
     for (int child_idx = 0; child_idx <= tr.number_of_split_sides(); ++child_idx) {
         assert(child_idx < int(m_triangles.size()) && m_triangles[child_idx].valid());
         if (m_triangles[tr.children[child_idx]].is_split())
-            remove_useless_children(tr.children[child_idx]);
+            children_removed |= remove_useless_children(tr.children[child_idx]);
     }
 
-
     // Return if a child is not leaf or two children differ in type.
     TriangleStateType first_child_type = TriangleStateType::NONE;
     for (int child_idx = 0; child_idx <= tr.number_of_split_sides(); ++child_idx) {
         if (m_triangles[tr.children[child_idx]].is_split())
-            return;
+            return children_removed;
         if (child_idx == 0)
             first_child_type = m_triangles[tr.children[0]].get_state();
         else if (m_triangles[tr.children[child_idx]].get_state() != first_child_type)
-            return;
+            return children_removed;
     }
 
     // If we got here, the children can be removed.
     undivide_triangle(facet_idx);
     tr.set_state(first_child_type);
+    return true;
 }
 
 void TriangleSelector::garbage_collect()
@@ -2050,7 +2057,22 @@ void TriangleSelector::seed_fill_unselect_all_triangles()
             triangle.unselect_by_seed_fill();
 }
 
+void TriangleSelector::seed_fill_unselect_triangle(const int facet_idx) {
+    assert(facet_idx > 0 && facet_idx < m_triangles.size());
+    Triangle &triangle = m_triangles[facet_idx];
+
+    assert(!triangle.is_split());
+    if (!triangle.is_split())
+        triangle.unselect_by_seed_fill();
+}
+
 void TriangleSelector::seed_fill_apply_on_triangles(TriangleStateType new_state) {
+    if (m_triangle_selected_by_seed_fill != -1) {
+        this->seed_fill_apply_on_single_triangle(new_state, m_triangle_selected_by_seed_fill);
+        m_triangle_selected_by_seed_fill = -1;
+        return;
+    }
+
     for (Triangle &triangle : m_triangles)
         if (!triangle.is_split() && triangle.is_selected_by_seed_fill())
             triangle.set_state(new_state);
@@ -2062,6 +2084,15 @@ void TriangleSelector::seed_fill_apply_on_triangles(TriangleStateType new_state)
         }
 }
 
+void TriangleSelector::seed_fill_apply_on_single_triangle(TriangleStateType new_state, const int facet_idx) {
+    assert(facet_idx > 0 && facet_idx < m_triangles.size());
+
+    if (Triangle &triangle = m_triangles[facet_idx]; !triangle.is_split() && triangle.is_selected_by_seed_fill()) {
+        triangle.set_state(new_state);
+        remove_useless_children(triangle.source_triangle);
+    }
+}
+
 double TriangleSelector::get_triangle_area(const Triangle &triangle) const {
     const stl_vertex &v0 = m_vertices[triangle.verts_idxs[0]].v;
     const stl_vertex &v1 = m_vertices[triangle.verts_idxs[1]].v;

src/libslic3r/TriangleSelector.hpp

@@ -401,10 +401,17 @@ public:
     // For all triangles, remove the flag indicating that the triangle was selected by seed fill.
     void seed_fill_unselect_all_triangles();
 
+    // Remove the flag indicating that the triangle was selected by seed fill.
+    void seed_fill_unselect_triangle(int facet_idx);
+
     // For all triangles selected by seed fill, set new TriangleStateType and remove flag indicating that triangle was selected by seed fill.
     // The operation may merge split triangles if they are being assigned the same color.
     void seed_fill_apply_on_triangles(TriangleStateType new_state);
 
+    // For the triangle selected by seed fill, set a new TriangleStateType and remove the flag indicating that the triangle was selected by seed fill.
+    // The operation may merge a split triangle if it is being assigned the same color.
+    void seed_fill_apply_on_single_triangle(TriangleStateType new_state, const int facet_idx);
+
     // Compute total area of the triangle.
     double get_triangle_area(const Triangle &triangle) const;
 
@@ -495,13 +502,16 @@ protected:
 
     std::unique_ptr<Cursor> m_cursor;
 
+    // Single triangle selected by seed fill. It is used to optimize painting using a single triangle brush.
+    int m_triangle_selected_by_seed_fill = -1;
+
     // Private functions:
 private:
     bool select_triangle(int facet_idx, TriangleStateType type, bool triangle_splitting);
     bool select_triangle_recursive(int facet_idx, const Vec3i &neighbors, TriangleStateType type, bool triangle_splitting);
     void undivide_triangle(int facet_idx);
     void split_triangle(int facet_idx, const Vec3i &neighbors);
-    void remove_useless_children(int facet_idx); // No hidden meaning. Triangles are meant.
+    bool remove_useless_children(int facet_idx); // No hidden meaning. Triangles are meant.
     bool is_facet_clipped(int facet_idx, const ClippingPlane &clp) const;
     int  push_triangle(int a, int b, int c, int source_triangle, TriangleStateType state = TriangleStateType::NONE);
     void perform_split(int facet_idx, const Vec3i &neighbors, TriangleStateType old_state);

src/slic3r/GUI/Gizmos/GLGizmoPainterBase.cpp

@@ -645,7 +645,9 @@ bool GLGizmoPainterBase::gizmo_event(SLAGizmoEventType action, const Vec2d& mous
                     assert(projected_mouse_position.mesh_idx == mesh_idx);
                     const Vec3f mesh_hit  = projected_mouse_position.mesh_hit;
                     const int   facet_idx = int(projected_mouse_position.facet_idx);
+
                     m_triangle_selectors[mesh_idx]->seed_fill_apply_on_triangles(new_state);
+
                     if (m_tool_type == ToolType::SMART_FILL) {
                         m_triangle_selectors[mesh_idx]->seed_fill_select_triangles(mesh_hit, facet_idx, trafo_matrix_not_translate, clp, m_smart_fill_angle, m_smart_fill_gap_area,
                                                                                    (m_paint_on_overhangs_only ? m_highlight_by_angle_threshold_deg : 0.f), TriangleSelector::ForceReselection::YES);