Improvements to EffectLine in sprites

examples/game/example_effect_line.dart

@@ -42,19 +42,20 @@ class TestApp extends App {
   List<String> _labelTexts = [
     "Colored",
     "Smoke",
-    "Electric"
+    "Electric",
+    "Rocket Trail"
   ];
 
   Widget build() {
     ThemeData theme = new ThemeData(
       brightness: ThemeBrightness.light,
-      primarySwatch: Colors.purple
+      primarySwatch: Colors.blue
     );
 
     return new Theme(
       data: theme,
       child: new Title(
-        title: 'Test drawAtlas',
+        title: 'EffectLine Demo',
         child: _buildColumn()
       )
     );
@@ -114,11 +115,10 @@ class TestBed extends NodeWithSize {
       // Create a line with no texture and a color sequence
       _line = new EffectLine(
         texture: null,
-        colorSequence: new ColorSequence.fromStartAndEndColor(new Color(0xffff0000), new Color(0xff0000ff)),
+        colorSequence: new ColorSequence.fromStartAndEndColor(new Color(0xaaffff00), new Color(0xaaff9900)),
         widthMode: EffectLineWidthMode.barrel,
-        minWidth: 20.0,
-        maxWidth: 50.0,
-        animationMode: EffectLineAnimationMode.scroll,
+        minWidth: 10.0,
+        maxWidth: 15.0,
         fadeAfterDelay: 1.0,
         fadeDuration: 1.0
       );
@@ -147,6 +147,20 @@ class TestBed extends NodeWithSize {
         maxWidth: 100.0,
         animationMode: EffectLineAnimationMode.random
       );
+    } else if (lineType == "Rocket Trail") {
+      Texture baseTexture = new Texture(_images['assets/line_effects.png']);
+      Texture trailLineTexture = baseTexture.textureFromRect(new Rect.fromLTRB(0.0, 896.0, 1024.0, 1024.0));
+
+      _line = new EffectLine(
+        texture: trailLineTexture,
+        textureLoopLength: 300.0,
+        widthMode: EffectLineWidthMode.barrel,
+        minWidth: 20.0,
+        maxWidth: 40.0,
+        widthGrowthSpeed: 40.0,
+        fadeAfterDelay: 0.5,
+        fadeDuration: 1.5
+      );
     }
 
     addChild(_line);

packages/flutter_sprites/lib/effect_line.dart

@@ -15,12 +15,15 @@ class EffectLine extends Node {
 
   EffectLine({
     this.texture: null,
+    this.transferMode: sky.TransferMode.dstOver,
     List<Point> points,
     this.widthMode : EffectLineWidthMode.linear,
     this.minWidth: 10.0,
     this.maxWidth: 10.0,
+    this.widthGrowthSpeed: 0.0,
     this.animationMode: EffectLineAnimationMode.none,
     this.scrollSpeed: 0.1,
+    double scrollStart: 0.0,
     this.fadeDuration: null,
     this.fadeAfterDelay: null,
     this.textureLoopLength: null,
@@ -36,15 +39,20 @@ class EffectLine extends Node {
         new Color(0xffffffff),
         new Color(0xffffffff));
 
+    _offset = scrollStart;
+
     _painter = new TexturedLinePainter(points, _colors, _widths, texture);
     _painter.textureLoopLength = textureLoopLength;
   }
 
   final Texture texture;
 
+  final sky.TransferMode transferMode;
+
   final EffectLineWidthMode widthMode;
   final double minWidth;
   final double maxWidth;
+  final double widthGrowthSpeed;
 
   final EffectLineAnimationMode animationMode;
   final double scrollSpeed;
@@ -86,14 +94,25 @@ class EffectLine extends Node {
       _offset = randomDouble();
     }
 
-    // Update age of line points, and remove if neccessary
+    // Update age of line points and remove if neccesasry
     if (fadeDuration != null && fadeAfterDelay != null) {
+      // Increase age of points
       for (int i = _points.length - 1; i >= 0; i--) {
         _pointAges[i] += dt;
-        if (_pointAges[i] > (fadeDuration + fadeAfterDelay)) {
-          _pointAges.removeAt(i);
-          _points.removeAt(i);
+      }
+
+      // Check if the first/oldest point should be removed
+      while(_points.length > 0 && _pointAges[0] > (fadeDuration + fadeAfterDelay)) {
+        // Update scroll if it isn't the last and only point that is about to removed
+        if (_points.length > 1 && textureLoopLength != null) {
+          double dist = GameMath.pointQuickDist(_points[0], _points[1]);
+          _offset = (_offset - (dist / textureLoopLength)) % 1.0;
+          if (_offset < 0.0) _offset += 1;
         }
+
+        // Remove the point
+        _pointAges.removeAt(0);
+        _points.removeAt(0);
       }
     }
   }
@@ -101,8 +120,6 @@ class EffectLine extends Node {
   void paint(PaintingCanvas canvas) {
     if (points.length < 2) return;
 
-    //_painter.textureLoopLength = textureLoopLength;
-
     _painter.points = points;
 
     // Calculate colors
@@ -127,12 +144,14 @@ class EffectLine extends Node {
 
     // Calculate widths
     List<double> widths = [];
-    for (double stop in stops) {
+    for (int i = 0; i < stops.length; i++) {
+      double stop = stops[i];
+      double growth = math.max(widthGrowthSpeed * _pointAges[i], 0.0);
       if (widthMode == EffectLineWidthMode.linear) {
-        double width = minWidth + (maxWidth - minWidth) * stop;
+        double width = minWidth + (maxWidth - minWidth) * stop + growth;
         widths.add(width);
       } else if (widthMode == EffectLineWidthMode.barrel) {
-        double width = minWidth + math.sin(stop * math.PI) * (maxWidth - minWidth);
+        double width = minWidth + math.sin(stop * math.PI) * (maxWidth - minWidth) + growth;
         widths.add(width);
       }
     }
@@ -148,12 +167,38 @@ class EffectLine extends Node {
     if (points.length > 0 && point.x == points[points.length - 1].x && point.y == points[points.length - 1].y)
       return;
 
-    if (simplify) {
+    if (simplify && points.length >= 2 && GameMath.pointQuickDist(point, points[points.length - 2]) < 10.0) {
+      // Check if we should remove last point before adding the new one
 
+      // Calculate the square distance from the middle point to the line of the
+      // new point and the second to last point
+      double dist2 = _distToSeqment2(
+        points[points.length - 1],
+        point,
+        points[points.length - 2]
+      );
+
+      // If the point is on the line, remove it
+      if (dist2 < 1.0) {
+        _points.removeAt(_points.length - 1);
+      }
     }
 
     // Add point and point's age
     _points.add(point);
     _pointAges.add(0.0);
   }
+
+  double _sqr(double x) => x * x;
+
+  double _dist2(Point v, Point w) => _sqr(v.x - w.x) + _sqr(v.y - w.y);
+
+  double _distToSeqment2(Point p, Point v, Point w) {
+    double l2 = _dist2(v, w);
+    if (l2 == 0.0) return _dist2(p, v);
+    double t = ((p.x - v.x) * (w.x - v.x) + (p.y - v.y) * (w.y - v.y)) / l2;
+    if (t < 0) return _dist2(p, v);
+    if (t > 1) return _dist2(p, w);
+    return _dist2(p, new Point(v.x + t * (w.x - v.x), v.y + t * (w.y - v.y)));
+  }
 }

packages/flutter_sprites/lib/textured_line.dart

@@ -75,6 +75,8 @@ class TexturedLinePainter {
     _calculatedTextureStops = null;
   }
 
+  sky.TransferMode transferMode = sky.TransferMode.srcOver;
+
   Paint _cachedPaint = new Paint();
 
   void paint(PaintingCanvas canvas) {
@@ -85,6 +87,8 @@ class TexturedLinePainter {
     assert(_points.length == colors.length);
     assert(_points.length == widths.length);
 
+    _cachedPaint.transferMode = transferMode;
+
     // Calculate normals
     List<Vector2> vectors = [];
     for (Point pt in _points) {
@@ -216,7 +220,13 @@ Vector2 _computeMiter(Vector2 lineA, Vector2 lineB) {
   Vector2 miter = new Vector2(- (lineA[1] + lineB[1]), lineA[0] + lineB[0]);
   miter.normalize();
 
-  double miterLength = 1.0 / dot2(miter, new Vector2(-lineA[1], lineA[0]));
+  double dot = dot2(miter, new Vector2(-lineA[1], lineA[0]));
+  if (dot.abs() < 0.1) {
+    miter = _vectorNormal(lineA).normalize();
+    return miter;
+  }
+
+  double miterLength = 1.0 / dot;
   miter = miter.scale(miterLength);
 
   return miter;