Playable demo game and bug fixes in sprites

sky/examples/game/lib/game_demo_world.dart

Index: sky/examples/game/lib/game_demo_world.dart
diff --git a/sky/examples/game/lib/game_demo_world.dart b/sky/examples/game/lib/game_demo_world.dart
new file mode 100644
index 0000000000000000000000000000000000000000..4344df19f0f62ef90d7035c84f46f99ab4befd7d
--- /dev/null
+++ b/sky/examples/game/lib/game_demo_world.dart
@@ -0,0 +1,285 @@
+part of game;
+
+// Random generator
+Math.Random _rand = new Math.Random();
+
+const double _gameSizeWidth = 1024.0;
+const double _gameSizeHeight = 1024.0;
+
+const double _shipRadius = 30.0;
+const double _lrgAsteroidRadius = 40.0;
+const double _medAsteroidRadius = 20.0;
+const double _smlAsteroidRadius = 10.0;
+const double _maxAsteroidSpeed = 1.0;
+
+const int _lifeTimeLaser = 50;
+
+class GameDemoWorld extends NodeWithSize {
+
+  // Images
+  Image _imgBg;
+  Image _imgAsteroid;
+  Image _imgShip;
+  Image _imgLaser;
+
+  // Inputs
+  double _joystickX = 0.0;
+  double _joystickY = 0.0;
+  bool _fire;
+
+  Ship _ship;
+  List<Asteroid> _asteroids = [];
+  List<Laser> _lasers = [];
+  
+  GameDemoWorld(ImageMap images) : super.withSize(new Size(_gameSizeWidth, _gameSizeHeight)) {
+
+    // Fetch images
+    _imgBg = images["https://raw.githubusercontent.com/slembcke/GalacticGuardian.spritebuilder/GDC/Packages/SpriteBuilder%20Resources.sbpack/resources-auto/BurnTexture.png"];
+    _imgAsteroid = images["https://raw.githubusercontent.com/slembcke/GalacticGuardian.spritebuilder/GDC/Packages/SpriteBuilder%20Resources.sbpack/Sprites/resources-auto/asteroid_big_002.png"];
+    _imgShip = images["https://raw.githubusercontent.com/slembcke/GalacticGuardian.spritebuilder/GDC/Packages/SpriteBuilder%20Resources.sbpack/Sprites/resources-auto/GG_blueship_Lv3.png"];
+    _imgLaser = images["https://raw.githubusercontent.com/slembcke/GalacticGuardian.spritebuilder/GDC/Packages/SpriteBuilder%20Resources.sbpack/Sprites/resources-auto/laserBlue.png"];
+
+    // Add some asteroids to the game world
+    for (int i = 0; i < 5; i++) {
+      addAsteroid(AsteroidSize.large);
+    }
+    for (int i = 0; i < 5; i++) {
+      addAsteroid(AsteroidSize.medium);
+    }
+
+    // Add ship
+    addShip();
+  }
+
+  // Methods for adding game objects
+
+  void addBackground() {
+    Sprite sprtBg = new Sprite.withImage(_imgBg);
+    sprtBg.size = new Size(_gameSizeWidth, _gameSizeHeight);
+    sprtBg.pivot = Point.origin;
+    this.addChild(sprtBg);
+  }
+  
+  void addAsteroid(AsteroidSize size, [Point pos]) {
+    Asteroid asteroid = new Asteroid.withImage(_imgAsteroid, size);
+    asteroid.zPosition = 1.0;
+    if (pos != null) asteroid.position = pos;
+    this.addChild(asteroid);
+    _asteroids.add(asteroid);
+  }
+
+  void addShip() {
+    Ship ship = new Ship.withImage(_imgShip);
+    ship.zPosition = 10.0;
+    this.addChild(ship);
+    _ship = ship;
+  }
+
+  void addLaser() {
+    Laser laser = new Laser.withImage(_imgLaser, _ship);
+    laser.zPosition = 8.0;
+    _lasers.add(laser);
+    this.addChild(laser);
+  }
+  
+  void update(double dt) {
+    // Move asteroids
+    for (Asteroid asteroid in _asteroids) {
+      asteroid.position = pointAdd(asteroid.position, asteroid._movementVector);
+    }
+
+    // Move lasers and remove expired lasers
+    for (int i = _lasers.length - 1; i >= 0; i--) {
+      Laser laser = _lasers[i];
+      laser.move();
+      if (laser._frameCount > _lifeTimeLaser) {
+        laser.removeFromParent();
+        _lasers.removeAt(i);
+      }
+    }
+
+    // Apply thrust to ship
+    if (_joystickX != 0.0 || _joystickY != 0.0) {
+      _ship.thrust(_joystickX, _joystickY);
+    }
+
+    // Move ship
+    _ship.move();
+
+    // Check collisions between asteroids and lasers
+    for (int i = _lasers.length -1; i >= 0; i--) {
+      // Iterate over all the lasers
+      Laser laser = _lasers[i];
+
+      for (int j = _asteroids.length - 1; j >= 0; j--) {
+        // Iterate over all the asteroids
+        Asteroid asteroid = _asteroids[j];
+
+        // Check for collision
+        if (pointQuickDist(laser.position, asteroid.position) < laser.radius + asteroid.radius) {
+          // Remove laser
+          laser.removeFromParent();
+          _lasers.removeAt(i);
+
+          // Add asteroids
+          if (asteroid._asteroidSize == AsteroidSize.large) {
+            for (int a = 0; a < 3; a++) addAsteroid(AsteroidSize.medium, asteroid.position);
+          }
+          else if (asteroid._asteroidSize == AsteroidSize.medium) {
+            for (int a = 0; a < 5; a++) addAsteroid(AsteroidSize.small, asteroid.position);
+          }
+
+          // Remove asteroid
+          asteroid.removeFromParent();
+          _asteroids.removeAt(j);
+          break;
+        }
+      }
+    }
+
+    // Move objects to center camera and warp objects around the edges
+    centerCamera();
+    warpObjects();
+  }
+
+  void centerCamera() {
+    const cameraDampening = 0.1;
+    Point delta = new Point(_gameSizeWidth/2 - _ship.position.x, _gameSizeHeight/2 - _ship.position.y);
+    delta = pointMult(delta, cameraDampening);
+
+    for (Node child in children) {
+      child.position = pointAdd(child.position, delta);
+    }
+  }
+
+  void warpObjects() {
+    for (Node child in children) {
+      if (child.position.x < 0) child.position = pointAdd(child.position, new Point(_gameSizeWidth, 0.0));
+      if (child.position.x >= _gameSizeWidth) child.position = pointAdd(child.position, new Point(-_gameSizeWidth, 0.0));
+      if (child.position.y < 0) child.position = pointAdd(child.position, new Point(0.0, _gameSizeHeight));
+      if (child.position.y >= _gameSizeHeight) child.position = pointAdd(child.position, new Point(0.0, -_gameSizeHeight));
+    }
+  }
+
+  // Handling controls
+
+  void controlSteering(double x, double y) {
+    _joystickX = x;
+    _joystickY = y;
+  }
+
+  void controlFire() {
+    addLaser();
+  }
+}
+
+// Game objects
+
+enum AsteroidSize {
+  small,
+  medium,
+  large,
+}
+
+class Asteroid extends Sprite {
+  Point _movementVector;
+  AsteroidSize _asteroidSize;
+  double _radius;
+
+  double get radius {
+    if (_radius != null) return _radius;
+    if (_asteroidSize == AsteroidSize.small) _radius = _smlAsteroidRadius;
+    else if (_asteroidSize == AsteroidSize.medium) _radius = _medAsteroidRadius;
+    else if (_asteroidSize == AsteroidSize.large) _radius = _lrgAsteroidRadius;
+    return _radius;
+  }
+
+  Asteroid.withImage(Image img, AsteroidSize this._asteroidSize) : super.withImage(img) {
+    size = new Size(radius * 2.0, radius * 2.0);
+    position = new Point(_gameSizeWidth * _rand.nextDouble(), _gameSizeHeight * _rand.nextDouble());
+    rotation = 360.0 * _rand.nextDouble();
+
+    _movementVector = new Point(_rand.nextDouble() * _maxAsteroidSpeed * 2 - _maxAsteroidSpeed,
+                                _rand.nextDouble() * _maxAsteroidSpeed * 2 - _maxAsteroidSpeed);
+  }
+}
+
+class Ship extends Sprite {
+  Vector2 _movementVector;
+  double _rotationTarget;
+
+  Ship.withImage(Image img) : super.withImage(img) {
+    _movementVector = new Vector2.zero();
+    rotation = _rotationTarget = 270.0;
+
+    // Create sprite
+    size = new Size(_shipRadius * 2.0, _shipRadius * 2.0);
+    position = new Point(_gameSizeWidth/2.0, _gameSizeHeight/2.0);
+  }
+
+  void thrust(double x, double y) {
+    _rotationTarget = convertRadians2Degrees(Math.atan2(y, x));
+    Vector2 directionVector = new Vector2(x, y).normalize();
+    _movementVector.addScaled(directionVector, 1.0);
+  }
+
+  void move() {
+    position = new Point(position.x + _movementVector[0], position.y + _movementVector[1]);
+    _movementVector.scale(0.9);
+
+    rotation = dampenRotation(rotation, _rotationTarget, 0.1);
+  }
+}
+
+class Laser extends Sprite {
+  int _frameCount = 0;
+  Point _movementVector;
+  double radius = 10.0;
+
+  Laser.withImage(Image img, Ship ship) : super.withImage(img) {
+    size = new Size(20.0, 20.0);
+    position = ship.position;
+    rotation = ship.rotation + 90.0;
+    transferMode = TransferMode.plusMode;
+    double rotRadians = convertDegrees2Radians(rotation);
+    _movementVector = pointMult(new Point(Math.sin(rotRadians), -Math.cos(rotRadians)), 10.0);
+    _movementVector = new Point(_movementVector.x + ship._movementVector[0], _movementVector.y + ship._movementVector[1]);
+  }
+
+  bool move() {
+    position = pointAdd(position, _movementVector);
+    _frameCount++;
+  }
+}
+
+// Convenience methods
+
+Point pointAdd(Point a, Point b) {
+  return new Point(a.x+ b.x, a.y + b.y);
+}

[abarth-chromium, 2015/06/13 00:03:20]

We have an operator+ for Point and Size.  I wonder how many of the |b| arguments
might be better represented as Sizes.  The difference between a Point and a Size
is that a Point represents a location in a coordinate system and Size represents
a displacement in the coordinate system.

+
+Point pointMult(Point a, double multiplier) {
+  return new Point(a.x * multiplier, a.y * multiplier);
+}

[abarth-chromium, 2015/06/13 00:03:20]

We should just add this to Point.dart

+
+double dampenRotation(double src, double dst, double dampening) {
+  double delta = dst - src;
+  while (delta > 180.0) delta -= 360;
+  while (delta < -180) delta += 360;
+  delta *= dampening;
+
+  return src + delta;
+}
+
+double pointQuickDist(Point a, Point b) {
+  double dx = a.x - b.x;
+  double dy = a.y - b.y;
+  if (dx < 0.0) dx = -dx;
+  if (dy < 0.0) dy = -dy;
+  if (dx > dy) {
+    return dx + dy/2.0;
+  }
+  else {
+    return dy + dx/2.0;
+  }
+}