Lumen Reflection Artifact for a Bathroom Mirror

[dragonhuang97]

Hello,

The reflection of the sink in the bathroom mirror is looking horrible. I tried both planar reflection and lumen reflection but the ugly black triangles were present in both cases.

When I visualized the lumen scene, it seems that the black triangles were the parts where the GI couldn’t reach.
Is there a way to fix this?
Thanks in advance.

[alberto]

Hello @dragonhuang97
I recommend you to use raytracing in reflections!

LUMEN:

RAY:

LUMEN:

RAY:

But it seems is not a lumen problem, I think what is happening is because the model has not merged vertex and faces have wholes

[Arii (Ari)]

have you tried increasing the reflection capture resolution inside project settings?

[dragonhuang97]

Thanks for your reply. I tried setting the reflection to ray-traced. While the black artefacts in the sink are gone, it seems to introduce other artifacts elsewhere.

I also included the model file for reference. I don’t think there is unmerged vertices in it
Test.fbx (83.7 KB)

[dragonhuang97]

Thanks for pointing this out. I did try to increase the reflection capture resolution but it didn’t seem to affect the black artifact.

[alberto]

Ok let’s take a look

[alberto]

@dragonhuang97

unmerged vertices

Ok I see several problems…

1.- Unmerged vertex:

2.- Geometry is not good, faces seem to be done by bool and not connected:

In fact if you see unreal tries to fix it:

3.-Wath is happening to your mirror is geometry is overlaping on y axis, just separate a bit!

4.- About the sink and the tap, no idea, the model you sent to me is not the complete scene, it seems a normal/vertex problem…

5.- If we are talking about mirrors, for final render… PathTracing is the King!

6.- Just in case… Remember setup lights for ray tracing, and samples per pixel

Tell me how is going!

[dragonhuang97]

Your path tracing result is phenomenal! However, I’m trying to create a real-time interactive archviz app (it’s actually my old apartment that I just moved out) so path tracing may fall short here.
After some search I think I found the cause of my original problem here.
It seems that lumen reflections rely on the surface cache it generates, and there’s a limited number of cards placed on each mesh.

In my case, the pink parts are black in the mirror because they don’t have surface cache coverage.

According to the UE doc, I tried increasing the max number of card for that particular mesh but it didn’t seem to fix the problem, so I guess the next thing to try is to separate the sink into smaller and less complicated meshes.
It’s gonna be a busy new week for me but I will keep you updated when I have any progress on this! Thanks a lot for the help!

[alberto]

@dragonhuang97

real-time interactive archviz ap

If we are talking about app like mobile, don’t use ray tracing…

[dragonhuang97]

Nah it’s a desktop application

[Arii (Ari)]

try increasing the mesh distant field resolution of the sink in the mesh editor see if this gets rid of the artifacts. note that this only effects the lumen reflections.

the artifacts in faucet in the raytraced Lumen reflection or the hit lighting method are because the reflection of a reflection only works in screen space so you get these black spots.

the only method to avoid these limitations is to use hardware raytracing or standalone ray traced (deprecated) in the PPV and that also has its own problems because while the reflections are sharp and accurate it does not reflect the GI of the scene so looks weird especially for interiors .