引用
Pixels are most probably the slowest part in your pipeline. The bigger the resolution, the more pixels we have to be shaded!

So how to check if we’re pixel-bound? While running our game, we can press ~ and enter: r.ScreenPercentage (for example) 25 or r.SetRes 480x270, for example. Then if your framerate improved a lot, then it means you’re pixel-bound. Not for example vertex- bound or memory-bound. The pixels are the problem.