setStencilMask( stencilMask ) {

		if ( this.currentStencilMask !== stencilMask ) {

			this.gl.stencilMask( stencilMask );
			this.currentStencilMask = stencilMask;

		}

	}
Specifies whether stencil values can be written when rendering
into a framebuffer or not.

This method caches the state so `gl.stencilMask()` is only
called when necessary.

@param {boolean} stencilMask - The stencil mask.