Source: Renderables/TextureRenderable_PixelCollision.js

  1. /* File: TextureRenderable_PixelCollision.js 
  2.  *
  3.  * Implements the pixelTouches() and related supporting functions of TextureRenderable
  4.  */
  6. /*jslint node: true, vars: true */
  7. /*global gEngine, TextureRenderable, vec2 */
  8. /* find out more about jslint: http://www.jslint.com/help.html */
  10. "use strict";  // Operate in Strict mode such that variables must be declared before used!
  12. /**
  13.  * Implements the pixelTouches() and related supporting functions of TextureRenderable
  14.  * @class TextureRenderable
  15.  * @param {TextureRenderable} other to check for collision with
  16.  * @param {vec2} wcTouchPos world coordinate position of first collision
  17.  * @returns {Boolean} true if collision is detected
  18.  */
  19. TextureRenderable.prototype.pixelTouches = function(other, wcTouchPos) {
  20.     var pixelTouch = false;
  21.     var xIndex = 0, yIndex;
  22.     var otherIndex = [0, 0];
  24.     var xDir = [1, 0];
  25.     var yDir = [0, 1];
  26.     var otherXDir = [1, 0];
  27.     var otherYDir = [0, 1];
  28.     vec2.rotate(xDir, xDir, this.mXform.getRotationInRad());
  29.     vec2.rotate(yDir, yDir, this.mXform.getRotationInRad());
  30.     vec2.rotate(otherXDir, otherXDir, other.mXform.getRotationInRad());
  31.     vec2.rotate(otherYDir, otherYDir, other.mXform.getRotationInRad());
  33.     while ((!pixelTouch) && (xIndex < this.mTexWidth)) {
  34.         yIndex = 0;
  35.         while ((!pixelTouch) && (yIndex < this.mTexHeight)) {
  36.             if (this._pixelAlphaValue(xIndex, yIndex) > 0) {
  37.                 this._indexToWCPosition(wcTouchPos, xIndex, yIndex, xDir, yDir);
  38.                 other._wcPositionToIndex(otherIndex, wcTouchPos, otherXDir, otherYDir);
  39.                 if ((otherIndex[0] >= 0) && (otherIndex[0] < other.mTexWidth) &&
  40.                     (otherIndex[1] >= 0) && (otherIndex[1] < other.mTexHeight)) {
  41.                     pixelTouch = other._pixelAlphaValue(otherIndex[0], otherIndex[1]) > 0;
  42.                 }
  43.             }
  44.             yIndex++;
  45.         }
  46.         xIndex++;
  47.     }
  48.     return pixelTouch;
  49. };
  51. /**
  52.  * Get the color array from the GPU and set it to the renderables Color Array
  53.  * @memberOf TextureRenderable
  54.  * @returns {void}
  55.  */
  56. TextureRenderable.prototype.setColorArray = function () {
  57.     if (this.mColorArray === null) {
  58.         this.mColorArray = gEngine.Textures.getColorArray(this.mTexture);
  59.     }
  60. };
  62. TextureRenderable.prototype._pixelAlphaValue = function (x, y) {
  63.     y += this.mTexBottomIndex;
  64.     x += this.mTexLeftIndex;
  65.     x = x * 4;
  66.     y = y * 4;
  67.     return this.mColorArray[(y * this.mTextureInfo.mWidth) + x  + 3];
  68. };
  70. TextureRenderable.prototype._wcPositionToIndex = function (returnIndex, wcPos, xDir, yDir) {
  71.     // use wcPos to compute the corresponding returnIndex[0 and 1]
  72.     var delta = [];
  73.     vec2.sub(delta, wcPos, this.mXform.getPosition());
  74.     var xDisp = vec2.dot(delta, xDir);
  75.     var yDisp = vec2.dot(delta, yDir);
  76.     returnIndex[0] = this.mTexWidth  * (xDisp / this.mXform.getWidth());
  77.     returnIndex[1] = this.mTexHeight * (yDisp / this.mXform.getHeight());
  79.     // recall that xForm.getPosition() returns center, yet
  80.     // Texture origin is at lower-left corner!
  81.     returnIndex[0] += this.mTexWidth / 2;
  82.     returnIndex[1] += this.mTexHeight / 2;
  84.     returnIndex[0] = Math.floor(returnIndex[0]);
  85.     returnIndex[1] = Math.floor(returnIndex[1]);
  86. };
  88. TextureRenderable.prototype._indexToWCPosition = function (returnWCPos, i, j, xDir, yDir) {
  89.     var x = i * this.mXform.getWidth() / this.mTexWidth;
  90.     var y = j * this.mXform.getHeight() / this.mTexHeight;
  91.     var xDisp = x - (this.mXform.getWidth() * 0.5);
  92.     var yDisp = y - (this.mXform.getHeight() * 0.5);
  93.     var xDirDisp = [];
  94.     var yDirDisp = [];
  96.     vec2.scale(xDirDisp, xDir, xDisp);
  97.     vec2.scale(yDirDisp, yDir, yDisp);
  98.     vec2.add(returnWCPos, this.mXform.getPosition(), xDirDisp);
  99.     vec2.add(returnWCPos, returnWCPos, yDirDisp);
  100. };
  102. //--- end of Public Methods
  103. //</editor-fold>