Hello,
We have an issue with Nanite and the Raytracing. For the project we are working we need to use the following command: `r.Lumen.ScreenProbeGather.ShortRangeAO.HardwareRayTracing`
Unfortunately with this command, when it comes to handle nanite fallbacks, we starts to see some artefacts as in this screenshot:
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We tried several things but always find out that we need to increase the fallback to a level close to 100% which makes non-sense to us.
We would like to know if you had any feedback regarding this workflow ?
Is there any good practice or advices to properly handle it ?
Thanks a lot.
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Hi,
thank you for the great repro scene. These sorts of issues are generally due to self-intersection and the divergence of the shading normal from the geometric normal, which is not available in the shader (this is a limitation of using HWRT).
Using higher poly geometry can reduce or eliminate the issue, but if that’s not a viable solution, increasing r.Lumen.ScreenProbeGather.ShortRangeAO.HardwareRayTracing.NormalBias from 0.1 to 0.3 or 0.4 should get rid of most artefacts (this CVar was introduced to mitigate this problem).
The relevant code that adds the bias to the normal can be found in the ApplyPositionBias() function in Shaders/Private/RayTracing/RayTracingCommon.ush
Let me know if this works or if you have more questions.
Regards,
Sam
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Hello,
Thank you for your answer and sorry for the delay regarding my answer. The team was able to test and figure out a solution for now thanks to your answer.
Thanks a lot
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Hi,
no problem. I will close the ticket, but please reopen if you have more questions.
Thanks,
Sam
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