docs: function DisplacementFilter(sprite)
  {
      var maskMatrix = new core.math.Matrix();
      sprite.renderable = false;
  
      core.AbstractFilter.call(this,
          // vertex shader
          fs.readFileSync(__dirname + '/displacement.vert', 'utf8'),
          // fragment shader
          fs.readFileSync(__dirname + '/displacement.frag', 'utf8'),
          // uniforms
          {
              mapSampler:     { type: 'sampler2D', value: sprite.texture },
              otherMatrix:    { type: 'mat3', value: maskMatrix.toArray(true) },
              scale:          { type: 'v2', value: { x: 1, y: 1 } }
          }
      );
  
      this.maskSprite = sprite;
      this.maskMatrix = maskMatrix;
  
  
      this.scale = new core.math.Point(20,20);
  
  }