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Very High GPU Usage When Using Foliage

Hello, for a long time the project I'm working on has been having very high GPU usage issues and it seems to be pushing even my GPU to the limit. I get constant 99% usage even on my GTX 1080 Ti. Some others on the project tested with GPUs which ranged from 960s to 1070 TIs and even with the latest drivers we still got the same issue.

After weeks of work, we've isolated the issue to be the foliage. The foliage appears to be culling correctly and using the appropriate LOD's. In addition, they're not high-poly meshes anyway. We've tried drastically decreasing the culling but we've seen no change We isolated the level by itself in its own project with none of game's source code whatsoever and only using the the default UE4 GameMode. Even then the issue happens so we're certain its nothing related to our code. However, if we turn off Foliage in the engine settings or use the console command to turn off Foliage while in-game, our usage drops dramatically from 99% by as much as 30% across the testing computers. If we set Foliage density to be lower, but still above 0, there is no change whatsoever. Only when the density is 0 do we see any change.

We're using Landscape Grass Types for the Foliage, not the actual Foliage tool. If we also just decrease the grass density in the Landscape Grass Type there's no change until we set it to 0. It seems immediately when we have a single instance of foliage we get the issue again. I've also tried different grass meshes just to be sure it wasn't the mesh, but no change no matter what.

Is this is a bug or is there anything that can explain why this is happening? We're using the 4.19 version of the engine as that's what the project was started in. Is this something that was fixed in a recent version? Any help would be appreciated and I can provide any info or things needed. We're really struggling with this as having no grass whatsoever looks ugly but at the moment that's the only thing that resolves the issue. Thank you!

Product Version: UE 4.19
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asked Mar 15 '19 at 03:02 AM in Rendering

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avatar image Xylord Mar 15 '19 at 09:04 AM

Does the issue arise as soon as there is a single instance of foliage? If not, how many are needed to cause a problem? Anything fancy happening in your grass shader? What is the shader complexity and quad overdraw when you use that grass?

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