Merge pull request #1299 from vlidholt/master

Removes artifacts from textured lines in sprites

packages/flutter_sprites/lib/textured_line.dart

@@ -75,6 +75,8 @@ class TexturedLinePainter {
     _calculatedTextureStops = null;
   }
 
+  bool removeArtifacts = true;
+
   sky.TransferMode transferMode = sky.TransferMode.srcOver;
 
   Paint _cachedPaint = new Paint();
@@ -184,8 +186,26 @@ class TexturedLinePainter {
     Offset offset0 = new Offset(miter[0] * halfWidth, miter[1] * halfWidth);
     Offset offset1 = new Offset(-miter[0] * halfWidth, -miter[1] * halfWidth);
 
-    vertices.add(point + offset0);
-    vertices.add(point + offset1);
+    Point vertex0 = point + offset0;
+    Point vertex1 = point + offset1;
+
+    int vertexCount = vertices.length;
+    if (removeArtifacts && vertexCount >= 2) {
+      Point oldVertex0 = vertices[vertexCount - 2];
+      Point oldVertex1 = vertices[vertexCount - 1];
+
+      Point intersection = GameMath.lineIntersection(oldVertex0, oldVertex1, vertex0, vertex1);
+      if (intersection != null) {
+        if (GameMath.pointQuickDist(vertex0, intersection) < GameMath.pointQuickDist(vertex1, intersection)) {
+          vertex0 = oldVertex0;
+        } else {
+          vertex1 = oldVertex1;
+        }
+      }
+    }
+
+    vertices.add(vertex0);
+    vertices.add(vertex1);
   }
 
   void _calculateTextureStops() {

packages/flutter_sprites/lib/util.dart

@@ -105,4 +105,29 @@ class GameMath {
   static Point filterPoint(Point a, Point b, double filterFactor) {
     return new Point(filter(a.x, b.x, filterFactor), filter(a.y, b.y, filterFactor));
   }
+
+  static Point lineIntersection(Point p, Point p2, Point q, Point q2) {
+    double epsilon = 1e-10;
+
+    Vector2 r = new Vector2(p2.x - p.x, p2.y - p.y);
+    Vector2 s = new Vector2(q2.x - q.x, q2.y - q.y);
+    Vector2 qp = new Vector2(q.x - p.x, q.y - p.y);
+
+    double rxs = cross2(r, s);
+
+    if (rxs.abs() < epsilon) {
+      // The lines are linear or collinear
+      return null;
+    }
+
+    double t = cross2(qp, s) / rxs;
+    double u = cross2(qp, r) / rxs;
+
+    if ((0.0 <= t && t <= 1.0) && (0.0 <= u && u <= 1.0)) {
+      return new Point(p.x + t * r.x, p.y + t * r.y);
+    }
+
+    // No intersection between the lines
+    return null;
+  }
 }