//void OnPreRender()
//{
//}
//private void OnRenderImage(RenderTexture source, RenderTexture destination)
//{
//}
//MSAA和HDR会激活unity内部的渲染流程必须走OnRenderImage（存疑）,所以事先关闭
private void OnPostRender()
{
Graphics.SetRenderTarget(rt);
GL.Clear(true, true, Color.grey);
CubeDraw.Draw(pureColorMaterial, cubeMesh);
SkyboxDraw.Draw(cam, skyboxMaterial);
Graphics.Blit(rt, cam.targetTexture);
}
