Substrate Rendering Issue with unwanted Specular Hits

[AkhilMajagaonkar]

I am trying to use substrate in my project using Lumen GI and Reflections and found some issues as there are some unwanted specular hits on surface indicated in the images posted below. These specular hits are more intense especially if the normal texture used in the material has intense modulation.

Project Settings:

I tried different debugging methods but was unsuccessful to get rid of the specular hits on the surface. Here are some cases mentioned below:

Case01: Tried setting Specular Scale to “0” on Directional Light but problem still persists.

Case02: Tested with scene using Default Megascans Albedo and Normal Texture and Substrate Slab BSDF-Simple in the material. But problem is still there

Case03: Problem still exists even when using Material with SubstrateUE4DefaultShading node in the material.

Case04: Tried to use Intense Normal modulated texture in the material and it seems to intensify the specular hits on the surface and make the surface appear more metallic. This is very strange behavior.

However, when I try to path trace the scene with same surface and Simple substrate BDSF material and there seems to be no unwanted specular hits and the material works and appears as expected.

Any idea what is happening here? This happens with any surface that has a strong normal and is not limited to megascans materials and textures.

To easily replicate the issue:

1. Create a default Unreal Engine scene with a directional light
2. Add a simple plan geometry
3. Add a simple single layered substrate material ideally with a strong normal such as this sand:
   https://quixel.com/megascans/home?search=thai&search=rippled&search=beach&search=sand&assetId=tefnah1q
4. After applying the material you will notice the weird specular hits as specific angles. Tweaking the roughness values, F0, and F90 values has no impact on mitigating these strange specular hits.
5. If you switch to pathtrace mode you will see a correct representation of the material

I am out of ideas and to me it seems like a significant bug in the substrate material system. Please advise.

Thank you.

[Leomerya12]

Graphics aren’t my forte, however, you can take a look at this thread… maybe it’ll give help/insight?

Certainly helped me with my issues with Lumen.

Lumen having a lot of noise in reflections in dark areas

I am experiencing Lumen Reflection Noise with Unreal Engine 5.3. @jblackwell Your explanation of the problem got me thinking and try a few different things. I found these settings that seem to be giving me much better results with Lumen Reflections with materials that have roughness, and significantly less noise. With these settings it looks much more realistic than the “screenspace” reflections, and not as good as pathtracing (obviously), but it’s something in the middle utilizing lumen refl…

[AkhilMajagaonkar]

It is not an issue with Lumen. The problem is with substrate material. The problem of unwanted specular hits persists with regular raytraced rendering pipeline and also with rasterized rendering with reflection probes. The only time I don’t get these specular hits with substrate material is when using path-tracing.