beginWithClear(r, g, b, a, stencilValue) {
    this.begin();
    this.clear(r, g, b, a, stencilValue);
  }
Begins redirecting drawing and clears the render pass. This is an optimized version of beginWithResetClear, and should only be used for fullscreen passes!
@param [r = 0] red clear value from 0 to 255
@param [g = 0] green clear value from 0 to 255
@param [b = 0] blue clear value from 0 to 255
@param [a = 0] alpha clear value from 0 to 255
@param [stencilValue = 0x0]