Refactors randomizations of color sequences and optimizes particle systems...

Refactors randomizations of color sequences and optimizes particle systems (uses single Paint instance, doesn't compute accelerations unless used, reduces number of created objects, faster color calculations)
Fixes indentation
Optimizes lookup in fast version of atan2 (toInt is faster than floor)
Removes frame rate printout and adds assert

packages/flutter/example/game/lib/color_secuence.dart

@@ -20,25 +20,6 @@ class ColorSequence {
     colorStops = new List<double>.from(sequence.colorStops);
   }
 
-  ColorSequence.copyWithVariance(ColorSequence sequence, int alphaVar, int redVar, int greenVar, int blueVar) {
-    colors = new List<Color>();
-    colorStops = new List<double>.from(sequence.colorStops);
-
-    for (Color color in sequence.colors) {
-      int aDelta = ((randomDouble() * 2.0 - 1.0) * alphaVar).toInt();
-      int rDelta = ((randomDouble() * 2.0 - 1.0) * redVar).toInt();
-      int gDelta = ((randomDouble() * 2.0 - 1.0) * greenVar).toInt();
-      int bDelta = ((randomDouble() * 2.0 - 1.0) * blueVar).toInt();
-
-      int aNew = (color.alpha + aDelta).clamp(0, 255);
-      int rNew = (color.red + rDelta).clamp(0, 255);
-      int gNew = (color.green + gDelta).clamp(0, 255);
-      int bNew = (color.blue + bDelta).clamp(0, 255);
-
-      colors.add(new Color.fromARGB(aNew, rNew, gNew, bNew));
-    }
-  }
-
   Color colorAtPosition(double pos) {
     assert(pos >= 0.0 && pos <= 1.0);
 

packages/flutter/example/game/lib/particle_system.dart

@@ -16,12 +16,18 @@ class _Particle {
   double timeToLive;
 
   Vector2 dir;
-  double radialAccel;
-  double tangentialAccel;
+
+  _ParticleAccelerations accelerations;
+
+  Float64List simpleColorSequence;
 
   ColorSequence colorSequence;
 }
 
+class _ParticleAccelerations {
+  double radialAccel;
+  double tangentialAccel;
+}
 
 class ParticleSystem extends Node {
 
@@ -76,10 +82,12 @@ class ParticleSystem extends Node {
   List<_Particle> _particles;
 
   double _emitCounter;
-  // Not yet used:
-  // double _elapsedTime;
   int _numEmittedParticles = 0;
 
+  static Paint _paint = new Paint()
+    ..setFilterQuality(FilterQuality.low)
+    ..isAntiAlias = false;
+
   ParticleSystem(this.texture,
                  {this.life: 1.5,
                   this.lifeVar: 1.0,
@@ -154,26 +162,35 @@ class ParticleSystem extends Node {
 
       // Update the particle
 
+      if (particle.accelerations != null) {
       // Radial acceleration
       Vector2 radial;
-      if (particle.pos[0] != 0 || particle.pos[1] != 0) {
-        radial = new Vector2.copy(particle.pos).normalize();
-      } else {
-        radial = new Vector2.zero();
+        if (particle.pos[0] != 0 || particle.pos[1] != 0) {
+          radial = new Vector2.copy(particle.pos).normalize();
+        } else {
+          radial = new Vector2.zero();
+        }
+        Vector2 tangential = new Vector2.copy(radial);
+        radial.scale(particle.accelerations.radialAccel);
+
+        // Tangential acceleration
+        double newY = tangential.x;
+        tangential.x = -tangential.y;
+        tangential.y = newY;
+        tangential.scale(particle.accelerations.tangentialAccel);
+
+        // (gravity + radial + tangential) * dt
+        Vector2 accel = (gravity + radial + tangential).scale(dt);
+        particle.dir += accel;
+      } else if (gravity[0] != 0.0 || gravity[1] != 0) {
+        // gravity
+        Vector2 accel = gravity.scale(dt);
+        particle.dir += accel;
       }
-      Vector2 tangential = new Vector2.copy(radial);
-      radial.scale(particle.radialAccel);
 
-      // Tangential acceleration
-      double newY = tangential.x;
-      tangential.x = -tangential.y;
-      tangential.y = newY;
-      tangential.scale(particle.tangentialAccel);
-
-      // (gravity + radial + tangential) * dt
-      Vector2 accel = (gravity + radial + tangential).scale(dt);
-      particle.dir += accel;
-      particle.pos += new Vector2.copy(particle.dir).scale(dt);
+      // Update particle position
+      particle.pos[0] += particle.dir[0] * dt;
+      particle.pos[1] += particle.dir[1] * dt;
 
       // Size
       particle.size = math.max(particle.size + particle.deltaSize * dt, 0.0);
@@ -182,7 +199,13 @@ class ParticleSystem extends Node {
       particle.rotation += particle.deltaRotation * dt;
 
       // Color
-      particle.colorPos = math.min(particle.colorPos + particle.deltaColorPos * dt, 1.0);
+      if (particle.simpleColorSequence != null) {
+        for (int i = 0; i < 4; i++) {
+          particle.simpleColorSequence[i] += particle.simpleColorSequence[i + 4] * dt;
+        }
+      } else {
+        particle.colorPos = math.min(particle.colorPos + particle.deltaColorPos * dt, 1.0);
+      }
     }
 
     if (autoRemoveOnFinish && _particles.length == 0 && _numEmittedParticles > 0) {
@@ -218,18 +241,50 @@ class ParticleSystem extends Node {
     double speedFinal = speed + speedVar * randomSignedDouble();
     particle.dir = dirVector.scale(speedFinal);
 
-    // Radial acceleration
-    particle.radialAccel = radialAcceleration + radialAccelerationVar * randomSignedDouble();
+    // Accelerations
+    if (radialAcceleration != 0.0 || radialAccelerationVar != 0.0 ||
+        tangentialAcceleration != 0.0 || tangentialAccelerationVar != 0.0) {
+      particle.accelerations = new _ParticleAccelerations();
 
-    // Tangential acceleration
-    particle.tangentialAccel = tangentialAcceleration + tangentialAccelerationVar * randomSignedDouble();
+      // Radial acceleration
+      particle.accelerations.radialAccel = radialAcceleration + radialAccelerationVar * randomSignedDouble();
+
+      // Tangential acceleration
+      particle.accelerations.tangentialAccel = tangentialAcceleration + tangentialAccelerationVar * randomSignedDouble();
+    }
 
     // Color
     particle.colorPos = 0.0;
     particle.deltaColorPos = 1.0 / particle.timeToLive;
 
     if (alphaVar != 0 || redVar != 0 || greenVar != 0 || blueVar != 0) {
-      particle.colorSequence = new ColorSequence.copyWithVariance(colorSequence, alphaVar, redVar, greenVar, blueVar);
+      particle.colorSequence = _ColorSequenceUtil.copyWithVariance(colorSequence, alphaVar, redVar, greenVar, blueVar);
+    }
+
+    // Optimizes the case where there are only two colors in the sequence
+    if (colorSequence.colors.length == 2) {
+      Color startColor;
+      Color endColor;
+
+      if (particle.colorSequence != null) {
+        startColor = particle.colorSequence.colors[0];
+        endColor = particle.colorSequence.colors[1];
+      } else {
+        startColor = colorSequence.colors[0];
+        endColor = colorSequence.colors[1];
+      }
+
+      // First 4 elements are start ARGB, last 4 are delta ARGB
+      particle.simpleColorSequence = new Float64List(8);
+      particle.simpleColorSequence[0] = startColor.alpha.toDouble();
+      particle.simpleColorSequence[1] = startColor.red.toDouble();
+      particle.simpleColorSequence[2] = startColor.green.toDouble();
+      particle.simpleColorSequence[3] = startColor.blue.toDouble();
+
+      particle.simpleColorSequence[4] = (endColor.alpha.toDouble() - startColor.alpha.toDouble()) / particle.timeToLive;
+      particle.simpleColorSequence[5] = (endColor.red.toDouble() - startColor.red.toDouble()) / particle.timeToLive;
+      particle.simpleColorSequence[6] = (endColor.green.toDouble() - startColor.green.toDouble()) / particle.timeToLive;
+      particle.simpleColorSequence[7] = (endColor.blue.toDouble() - startColor.blue.toDouble()) / particle.timeToLive;
     }
 
     _particles.add(particle);
@@ -242,6 +297,8 @@ class ParticleSystem extends Node {
     List<Rect> rects = [];
     List<Color> colors = [];
 
+    _paint.setTransferMode(transferMode);
+
     for (_Particle particle in _particles) {
       // Transform
       double scos;
@@ -250,9 +307,12 @@ class ParticleSystem extends Node {
         double extraRotation = GameMath.atan2(particle.dir[1], particle.dir[0]);
         scos = math.cos(convertDegrees2Radians(particle.rotation) + extraRotation) * particle.size;
         ssin = math.sin(convertDegrees2Radians(particle.rotation) + extraRotation) * particle.size;
-      } else {
+      } else if (particle.rotation != 0.0) {
         scos = math.cos(convertDegrees2Radians(particle.rotation)) * particle.size;
         ssin = math.sin(convertDegrees2Radians(particle.rotation)) * particle.size;
+      } else {
+        scos = particle.size;
+        ssin = 0.0;
       }
       RSTransform transform = new RSTransform(scos, ssin, particle.pos[0], particle.pos[1]);
       transforms.add(transform);
@@ -262,19 +322,55 @@ class ParticleSystem extends Node {
       rects.add(rect);
 
       // Color
-      Color particleColor;
-      if (particle.colorSequence != null) {
-        particleColor = particle.colorSequence.colorAtPosition(particle.colorPos);
+      if (particle.simpleColorSequence != null) {
+        Color particleColor = new Color.fromARGB(
+          particle.simpleColorSequence[0].toInt().clamp(0, 255),
+          particle.simpleColorSequence[1].toInt().clamp(0, 255),
+          particle.simpleColorSequence[2].toInt().clamp(0, 255),
+          particle.simpleColorSequence[3].toInt().clamp(0, 255));
+        colors.add(particleColor);
       } else {
-        particleColor = colorSequence.colorAtPosition(particle.colorPos);
+        Color particleColor;
+        if (particle.colorSequence != null) {
+          particleColor = particle.colorSequence.colorAtPosition(particle.colorPos);
+        } else {
+          particleColor = colorSequence.colorAtPosition(particle.colorPos);
+        }
+        colors.add(particleColor);
       }
-      colors.add(particleColor);
     }
 
-    Paint paint = new Paint()..setTransferMode(transferMode)
-        ..setFilterQuality(FilterQuality.low) // All Skia examples do this.
-        ..isAntiAlias = false; // Antialiasing breaks SkCanvas.drawAtlas?
     canvas.drawAtlas(texture.image, transforms, rects, colors,
-      TransferMode.modulate, null, paint);
+      TransferMode.modulate, null, _paint);
+  }
+}
+
+class _ColorSequenceUtil {
+  static ColorSequence copyWithVariance(
+    ColorSequence sequence,
+    int alphaVar,
+    int redVar,
+    int greenVar,
+    int blueVar
+  ) {
+    ColorSequence copy = new ColorSequence.copy(sequence);
+
+    int i = 0;
+    for (Color color in sequence.colors) {
+      int aDelta = ((randomDouble() * 2.0 - 1.0) * alphaVar).toInt();
+      int rDelta = ((randomDouble() * 2.0 - 1.0) * redVar).toInt();
+      int gDelta = ((randomDouble() * 2.0 - 1.0) * greenVar).toInt();
+      int bDelta = ((randomDouble() * 2.0 - 1.0) * blueVar).toInt();
+
+      int aNew = (color.alpha + aDelta).clamp(0, 255);
+      int rNew = (color.red + rDelta).clamp(0, 255);
+      int gNew = (color.green + gDelta).clamp(0, 255);
+      int bNew = (color.blue + bDelta).clamp(0, 255);
+
+      copy.colors[i] = new Color.fromARGB(aNew, rNew, gNew, bNew);
+      i++;
+    }
+
+    return copy;
   }
 }

packages/flutter/example/game/lib/sprite_box.dart

@@ -31,6 +31,10 @@ class SpriteBox extends RenderBox {
   void set rootNode (NodeWithSize value) {
     if (value == _rootNode) return;
 
+    // Ensure that the root node has a size
+    assert(value.size.width > 0);
+    assert(value.size.height > 0);
+
     // Remove sprite box references
     if (_rootNode != null) _removeSpriteBoxReference(_rootNode);
 
@@ -334,9 +338,9 @@ class SpriteBox extends RenderBox {
 
     _frameRate = 1.0/delta;
 
-    // Print frame rate
-    if (_numFrames % 60 == 0)
-      print("delta: $delta fps: $_frameRate");
+    // // Print frame rate
+    // if (_numFrames % 60 == 0)
+    //   print("delta: $delta fps: $_frameRate");
 
     _runActions(_rootNode, delta);
     _callUpdate(_rootNode, delta);

packages/flutter/example/game/lib/util.dart

@@ -57,26 +57,26 @@ class GameMath {
     if (x >= 0) {
       if (y >= 0) {
         if (x >= y)
-          return _atan2.ppy[(_Atan2Constants.size * y / x + 0.5).floor()];
+          return _atan2.ppy[(_Atan2Constants.size * y / x + 0.5).toInt()];
         else
-          return _atan2.ppx[(_Atan2Constants.size * x / y + 0.5).floor()];
+          return _atan2.ppx[(_Atan2Constants.size * x / y + 0.5).toInt()];
       } else {
         if (x >= -y)
-          return _atan2.pny[(_Atan2Constants.ezis * y / x + 0.5).floor()];
+          return _atan2.pny[(_Atan2Constants.ezis * y / x + 0.5).toInt()];
         else
-          return _atan2.pnx[(_Atan2Constants.ezis * x / y + 0.5).floor()];
+          return _atan2.pnx[(_Atan2Constants.ezis * x / y + 0.5).toInt()];
       }
     } else {
       if (y >= 0) {
         if (-x >= y)
-          return _atan2.npy[(_Atan2Constants.ezis * y / x + 0.5).floor()];
+          return _atan2.npy[(_Atan2Constants.ezis * y / x + 0.5).toInt()];
         else
-          return _atan2.npx[(_Atan2Constants.ezis * x / y + 0.5).floor()];
+          return _atan2.npx[(_Atan2Constants.ezis * x / y + 0.5).toInt()];
       } else {
         if (x <= y)
-          return _atan2.nny[(_Atan2Constants.size * y / x + 0.5).floor()];
+          return _atan2.nny[(_Atan2Constants.size * y / x + 0.5).toInt()];
         else
-          return _atan2.nnx[(_Atan2Constants.size * x / y + 0.5).floor()];
+          return _atan2.nnx[(_Atan2Constants.size * x / y + 0.5).toInt()];
       }
     }
   }