code: function(x, y) {
          var renderer = this.renderer;
  
          var ratio = this.downSampleRatio;
          x = Math.ceil(ratio * x);
          y = Math.ceil(ratio * (this.height - y));
  
          this._frameBuffer.bind(renderer);
          var pixel = new Uint8Array(4);
          var _gl = renderer.gl;
          // TODO out of bounds ?
          // preserveDrawingBuffer ?
          _gl.readPixels(x, y, 1, 1, _gl.RGBA, _gl.UNSIGNED_BYTE, pixel);
          this._frameBuffer.unbind(renderer);
          // Skip interpolated pixel because of anti alias
          if (pixel[3] === 255) {
              var id = unpackID(pixel[0], pixel[1], pixel[2]);
              if (id) {
                  var el = this._lookupTable[id - this.lookupOffset];
                  return el;
              }
          }
      }
docs: Pick the object
  @param  {number} x Mouse position x
  @param  {number} y Mouse position y
  @return {clay.Node}