_createRenderCmd() {
    if (cc._renderType === cc._RENDER_TYPE_CANVAS) {
      return this._super();
    }
    return new FXFireLinearWaveSprite.WebGLRenderCmd(this);
  }
*************************************************************************
FXFireLinearWaveSprite
 - use sprite.setTextureRect(cc.rect(x, y, w, h)) to define the size of the sprite
**************************************************************************