Ambient Occlusion and GPU Impact

Profile GPU shows ambient occlusion and indirect lighting as being a big hit to my FPS. When I bake my AO in substance 3D painter I have been using max secondary rays (200) and my question is whether that makes a difference in performance.

Should I re-bake all my textures?

Once it’s baked out, the only real performance factor is the resolution of the AO texture. That’s the main point of a baking, after all.

Usually when we’re talking about the performance cost of AO and/or indirect lighting, this is referring to real time effects like Lumen or SSAO, which has little to nothing to do with the materials/textures.
You can try switching off Lumen GI and AO for SSGI and SSAO for comparison.

Would you mind explaining what exactly SSAO and SSGI is?

I’m using Lumen. What is Lumen GI?

GI is global illumination. So Lumen is software/hardware Raytraced GI. SSGI is screen space GI and doesn’t use raytracing so it is less accurate but usually less expensive. SSAO is screen space ambient occlusion, it’s like screen space GI except it can only for darkening areas where there isn’t light instead of brightening. GI can refer to both ambient occlusion and bounced light.

Screen space techniques are the last gen tech but still widely used. Unreal has profiling tools you can use to see exactly what its spending time on. Textures aren’t a big issue as long as you don’t use too much memory.