Is “Force volumetric” setting on Static Meshes more expensive performance vise?
What I want to do is use it on HLODs.
I dont want 100k merged meshes to have lightmaps. They won’t bake lighting properly, if they bake it - its very rough and ugly, and their lightmap UVs are… well, imaging 500 meshes combined into one… So i want to have all my HLODs with forced to volumetric lighting. But HLODs are heavy in polygons and there are many of them… so, will this hinder my performance??
To answer my own question: forcing volumetric lightmap on static meshes (set to static mobility) doesn’t seem to impact performance. Only eats up some additional render target memory, but fps seems okay…
Ran a test. Got around 300 meshes of 110k each. Baked lighting, took a measure, then changed lightmap to volumetric. No difference at all, except the render target memory.
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You really probably shouldn’t be doing this in general, lightmaps aside.
More to your point, thanks for posting your test results. I would have guessed that you would save a little bit of texture memory since you wouldn’t be spending it on surface lightmaps, but I guess not.
One question:
Does this mean you didn’t rebake after switching to force volumetric? I’m curious if Unreal keeps the surface lightmaps in memory if you don’t rebake, seems like it shouldn’t but I know that in order to disable lightmass specifically you need to rebuild the lighting to clear out the existing lightmaps.
Decided to test this myself, I used memreport -full as described here and it appears that as expected, you do indeed save a lot of texture memory by using force volumetric.
Default (using Surface Lightmaps for static meshes)
Total TEXTUREGROUP_Lightmap size: InMem= 85.38 MB OnDisk= 85.38 MB
Force Volumetric
Total TEXTUREGROUP_Lightmap size: InMem= 0.38 MB OnDisk= 0.38 MB
Default
0.219MB - Texture memory 3D - STAT_TextureMemory3D - STATGROUP_RHI - STATCAT_Advanced
138.449MB - Texture memory 2D - STAT_TextureMemory2D - STATGROUP_RHI - STATCAT_Advanced
1.062MB - Render target memory Cube - STAT_RenderTargetMemoryCube - STATGROUP_RHI - STATCAT_Advanced
1.438MB - Render target memory 3D - STAT_RenderTargetMemory3D - STATGROUP_RHI - STATCAT_Advanced
424.250MB - Render target memory 2D - STAT_RenderTargetMemory2D - STATGROUP_RHI - STATCAT_Advanced
605.305MB total
Force Volumetric
0.219MB - Texture memory 3D - STAT_TextureMemory3D - STATGROUP_RHI - STATCAT_Advanced
53.004MB - Texture memory 2D - STAT_TextureMemory2D - STATGROUP_RHI - STATCAT_Advanced
1.062MB - Render target memory Cube - STAT_RenderTargetMemoryCube - STATGROUP_RHI - STATCAT_Advanced
1.438MB - Render target memory 3D - STAT_RenderTargetMemory3D - STATGROUP_RHI - STATCAT_Advanced
424.250MB - Render target memory 2D - STAT_RenderTargetMemory2D - STATGROUP_RHI - STATCAT_Advanced
520.431MB total