code: function clipRect(x, y, width, height) {
           var canvas = this.backBufferCanvas;
           var gl = this.gl; // if requested box is different from the current canvas size
  
           if (x !== 0 || y !== 0 || width !== canvas.width || height !== canvas.height) {
             var currentScissor = this.currentScissor;
  
             if (gl.isEnabled(gl.SCISSOR_TEST)) {
               // if same as the current scissor box do nothing
               if (currentScissor[0] === x && currentScissor[1] === y && currentScissor[2] === width && currentScissor[3] === height) {
                 return;
               }
             } // flush the compositor
  
  
             this.flush(); // turn on scissor test
  
             gl.enable(this.gl.SCISSOR_TEST); // set the scissor rectangle (note : coordinates are left/bottom)
  
             gl.scissor( // scissor does not account for currentTransform, so manually adjust
             x + this.currentTransform.tx, canvas.height - height - y - this.currentTransform.ty, width, height); // save the new currentScissor box
  
             currentScissor[0] = x;
             currentScissor[1] = y;
             currentScissor[2] = width;
             currentScissor[3] = height;
           } else {
             // turn off scissor test
             gl.disable(gl.SCISSOR_TEST);
           }
         }
docs: clip the given region from the original canvas. Once a region is clipped,
  all future drawing will be limited to the clipped region.
  You can however save the current region using the save(),
  and restore it (with the restore() method) any time in the future.
  (<u>this is an experimental feature !</u>)
  @name clipRect
  @memberOf me.WebGLRenderer.prototype
  @function
  @param {Number} x
  @param {Number} y
  @param {Number} width
  @param {Number} height