_renderBuffer() {
		const engine = this.scene.getEngine();
		engine.setDepthFunctionToLessOrEqual();

		//depth write
		engine.setColorWrite(false);
		this.effect.setFloat('alphaTest', 0.9);
		engine.drawElementsType(Material.TriangleFillMode, 0, this.sprites.length * 6);
		engine.setColorWrite(true);

		//diffuse
		this.effect.setFloat('alphaTest', -0.9);
		engine.setAlphaMode(Engine.ALPHA_COMBINE);
		engine.drawElementsType(Material.TriangleFillMode, 0, this.sprites.length * 6);
		engine.setAlphaMode(Engine.ALPHA_DISABLE);
		this.effect.setFloat('alphaTest', 0);
	}