From a9af3a9b17a7889cfa361bccc447d38d01c6b337 Mon Sep 17 00:00:00 2001
From: Yousef Khadadeh <erroratline0@gmail.com>
Date: Tue, 26 Aug 2025 17:41:08 +0300
Subject: [PATCH] Added brush LODs for SkPath brush stroke implementation

---
 src/DrawComponents/DrawBrushStroke.cpp | 28 ++++++++++++++++++++++----
 src/DrawComponents/DrawBrushStroke.hpp |  5 ++++-
 2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/src/DrawComponents/DrawBrushStroke.cpp b/src/DrawComponents/DrawBrushStroke.cpp
index 99a95ff..e2bbf67 100644
--- a/src/DrawComponents/DrawBrushStroke.cpp
+++ b/src/DrawComponents/DrawBrushStroke.cpp
@@ -42,6 +42,7 @@ std::shared_ptr<DrawComponent> DrawBrushStroke::deep_copy() const {
     a->coords = coords;
     // Just copy pointers over, brush strokes cant be edited so they can share the same memory
     a->brushPath = brushPath;
+    a->brushPathLOD = brushPathLOD;
     a->bounds = bounds;
 
     return a;
@@ -80,7 +81,10 @@ void DrawBrushStroke::draw(SkCanvas* canvas, const DrawData& drawData) {
         canvas->save();
         paint.setColor4f(SkColor4f{d->color.x(), d->color.y(), d->color.z(), d->color.w()});
         canvas_do_calculated_transform(canvas);
-        canvas->drawPath(*brushPath, paint);
+        if(drawSetupData.mipmapLevel == 0)
+            canvas->drawPath(*brushPath, paint);
+        else
+            canvas->drawPath(*brushPathLOD[drawSetupData.mipmapLevel - 1], paint);
         //SkPaint p2(SkColor4f{1, 0, 0, 1});
         //p2.setStroke(true);
         //SkPaint p3(SkColor4f{0, 1, 0, 1});
@@ -102,8 +106,12 @@ void DrawBrushStroke::initialize_draw_data(DrawingProgram& drawP) {
         };
 
         brushPath = std::make_shared<SkPath>();
+        brushPathLOD[0] = std::make_shared<SkPath>();
+        brushPathLOD[1] = std::make_shared<SkPath>();
 
         create_triangles(triangleFunc, points, 0, brushPath);
+        create_triangles(triangleFunc, points, 4, brushPathLOD[0]);
+        create_triangles(triangleFunc, points, 30, brushPathLOD[1]);
     }
     create_collider();
 }
@@ -196,10 +204,21 @@ std::vector<DrawBrushStrokePoint> DrawBrushStroke::smooth_points_avg(size_t begi
     return toRet;
 }
 
-void DrawBrushStroke::create_triangles(const std::function<bool(Vector2f, Vector2f, Vector2f)>& passTriangleFunc, const std::vector<DrawBrushStrokePoint>& points, unsigned skipVertexCount, std::shared_ptr<SkPath> bPath) {
+std::vector<DrawBrushStrokePoint> DrawBrushStroke::every_nth_point_include_front_and_back(const std::vector<DrawBrushStrokePoint>& pts, size_t n) {
+    if(pts.size() <= 3 || n == 0)
+        return pts;
+    std::vector<DrawBrushStrokePoint> toRet;
+    toRet.emplace_back(pts.front());
+    for(size_t i = n; i < pts.size() - 1; i += n)
+        toRet.emplace_back(pts[i]);
+    toRet.emplace_back(pts.back());
+    return toRet;
+}
+
+void DrawBrushStroke::create_triangles(const std::function<bool(Vector2f, Vector2f, Vector2f)>& passTriangleFunc, const std::vector<DrawBrushStrokePoint>& smoothedPoints, size_t skipVertexCount, std::shared_ptr<SkPath> bPath) {
     const int ARC_SMOOTHNESS = 10;
     const int CIRCLE_SMOOTHNESS = 20;
-    std::vector<DrawBrushStrokePoint>& pointsN = d->points;
+    const std::vector<DrawBrushStrokePoint>& pointsN = d->points;
     std::vector<SkPoint> topPoints;
     std::vector<SkPoint> bottomPoints;
 
@@ -217,6 +236,8 @@ void DrawBrushStroke::create_triangles(const std::function<bool(Vector2f, Vector
         return;
     }
 
+    auto points = every_nth_point_include_front_and_back(smoothedPoints, skipVertexCount);
+
     std::vector<size_t> wedgeIndices = get_wedge_indices(points);
     for(size_t i = 0; i < wedgeIndices.size() - 1; i++) {
 
@@ -250,7 +271,6 @@ void DrawBrushStroke::create_triangles(const std::function<bool(Vector2f, Vector
         }
 
         for(size_t j = pointsBegin + 1; j < pointsEnd; j++) {
-            j += skipVertexCount;
             if(j >= pointsEnd)
                 j = pointsEnd - 1;
 
diff --git a/src/DrawComponents/DrawBrushStroke.hpp b/src/DrawComponents/DrawBrushStroke.hpp
index 8e50a2d..bed14ee 100644
--- a/src/DrawComponents/DrawBrushStroke.hpp
+++ b/src/DrawComponents/DrawBrushStroke.hpp
@@ -49,10 +49,13 @@ class DrawBrushStroke : public DrawComponent {
         std::shared_ptr<SkPath> brushPath;
         SCollision::AABB<float> bounds;
 
+        std::array<std::shared_ptr<SkPath>, 2> brushPathLOD;
     private:
+        std::vector<DrawBrushStrokePoint> every_nth_point_include_front_and_back(const std::vector<DrawBrushStrokePoint>& pts, size_t n);
+
         void add_precheck_aabb_level(size_t level, const std::vector<SCollision::BVHContainer<float>>& levelArray);
         std::vector<SCollision::AABB<float>> precheckAABBLevels;
-        void create_triangles(const std::function<bool(Vector2f, Vector2f, Vector2f)>& passTriangleFunc, const std::vector<DrawBrushStrokePoint>& points, unsigned skipVertexCount, std::shared_ptr<SkPath> bPath);
+        void create_triangles(const std::function<bool(Vector2f, Vector2f, Vector2f)>& passTriangleFunc, const std::vector<DrawBrushStrokePoint>& smoothedPoints, size_t skipVertexCount, std::shared_ptr<SkPath> bPath);
         std::vector<size_t> get_wedge_indices(const std::vector<DrawBrushStrokePoint>& points);
         std::vector<DrawBrushStrokePoint> smooth_points(size_t beginIndex, size_t endIndex, unsigned numOfDivisions);
         std::vector<DrawBrushStrokePoint> smooth_points_avg(size_t beginIndex, size_t endIndex, unsigned numOfDivisions);