What are the performance impacts of the "Enable CSM Caching" setting?

Based on the name, I presume that this setting caches directional light shadow cascades in the RAM and loads them when needed. The description says that it will probably improve performance, but that’s a bit vague to me. Doesn’t Unreal already cache shadows in the RAM? I’m not using Lumen, so would this setting still have any benefits with Stationary and/or static lighting?

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From my limited testing and basic understanding, it seems to cache one of the higher cascade resolutions and renders it at a further distance using the cached data. I have attached 2 images from my test. Enabling the setting actually reduced my FPS very slightly, but the shadow quality went up. My drawcalls and triangle count also reduced, which is actually the same effect you would get if you reduced the number of dynamic shadow cascades on your directional light.

Note I am on 5.5.4 using forward rendering and this is only 1 datapoint, so your results may differ.