As far as I can tell, when using volumetric fog, the new local fog volumes basically do the same thing as a simple volumetric material on a mesh. Is there a big difference in terms of performance, and if so in what way, between the two methods? Providing of course that the volumetric material is simple math and no texture samples. Would love to get some insight into the differences between them.
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Hi Tor,
In terms of performance, LFVs and Volumetric Mesh Materials will likely depend a bit on your setup. Let me first give you the pros and cons of either technique:
Volumetric material on meshes:
+ Custom materials so you can have any shape, fall off, etc.
- Can only be voxelised into a volumetric fog distance range. After that, they disappear.
Local fog volume
+ Visible at any distance and can be voxelised in volumetric fog when they are close to the camera
+ Works on all platforms
- Simple shapes only (height fog in a sphere)
If you are considering local fog volumes, it is also worth noting that performance is heavily dependent on how many volumes you use, the overlap between volumes, and the screen-space coverage. You should avoid overlapping LFVs whenever possible and keep screen space coverage to a minimum.
There is a debug view mode that you can use, which is also called out in the public documentation on LFVs: https://dev.epicgames.com/documentation/en\-us/unreal\-engine/local\-fog\-volumes\-in\-unreal\-engine
Feel free to read that and let me know if you have any more questions.
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