Directional Light reflections on occluded geometry

Hi there, first time doing some tests in UE, this is 5.4.4.

In resume i have 3 main issues

1- Directional light reflects on occluded surfaces
2- Directional Light creates a foggy appearance in the car optics and car interior
3- This is different, Rectlights flicker on raytracing shadows if directional light is on.

I’m having this issue where directional light outside this “garage” (just a couple of planes) creates a fog-like volume inside the optics and car interior

And besides of that you can see the directional light reflection in the test ball over the car as it ignores the ceiling plane

Turning it off gives a better result of the translucency of the optics

and directional light on again creating the opaque/fog effect on the windshield…

And this is the shadow flickering issue when rectlight raytracing shadows is on as well as the directional light.

Now some info about the settings

The glass material is from the Automotive materials pack

It’s master material


I think that’s it, if someone has an idea how to solve it but need more information just ask for it, i don’t know if there is something else i can provide.

Specs:
Windows 10 x64 pro build 19045
Amd ryzen9 5950x
Rtx 3060 - 12GB
128GB ram

1 Like

Set the base color of your material to 0 and that should go away, it’s diffuse lighting from Lumen’s translucent lighting volume.

No idea why the specular highlight for the directional light would be visible, I can’t reproduce that in 5.5. May just be a bug with 5.4.

1 thing solved, thanks. Although i dont understand yet why this happens if the directional light is not hitting the surface.

Translucent materials can’t use Lumen’s screen probes because they’re placed directly on the depth buffer, but Translucent materials don’t write depth. So they fall back to being lit by Lumen’s translucent volume lighting, which is very sparse and prone to light leaking. (If I recall correctly the Lumen team originally warned that you’d see leaking on translucent surfaces within 2 meters of any wall)… At least this is my understanding of it.

When you’re using hit lighting for reflections it will usually only be an issue for diffuse lighting, which is why setting the base color to zero hides it, since the indirect specular is contributing most/all the lighting.

A while back in the Lumen feedback thread it was mentioned that the Lumen team was planning (or considering?) leveraging the fact that the translucent probes really only need to be in the camera frustum and not everywhere in worldspace, allocating most of the resolution toward what’s in frame would increase quality which should help address the leaking, but I’m not sure if this is something they’ve started work on yet.

The 3th issue, Shadow flickering problem solved by setting command r.Shadow.Denoiser 0
Somehow the raytraced shadows create the issue.