Ray Tracing On Glass Blocks Light

When I enable Ray Tracing Reflections, my head light glass seems to block the chrome material from creating reflections.

Ray Tracing Translucency seems to have no impact.

The glass is obviously a translucent material and I’ve read that " Translucent Materials currently act like an opaque material meaning that it does not allow light to pass through." The solution was said to be “open the static mesh that has the material applied and under the material slot, disable Cast Shadow for that specific material slot.”

I tried that solution but it didn’t work for me.

Anybody have any suggestions on how to get this working? Thanks!

Hi, there’s a thread in the Rendering forum from within the past year that deals with the issue of translucency and objects behind it in ray tracing. I’ll look for it in the subscribed list of threads I saved, then post a link to it. It’s a common issue, especially encountered in scenes with rendering cars.

Ok, so two links that could be useful. The first is for the issue of objects rendering black behind translucent glass.


It seems to be an issue of the inner face of the glass reflecting the interior meshes and their materials back at them with the shadow being solid black (a few different causes of solid black shadows from RT translucency). It could be something else, though, so I suggest trying a change based on the postings in the thread linked above.

The second link is for a series of fixes that may or may not help with other ray tracing issues. It might also help in understanding what’s involved in the ray tracing reflections and translucency dynamics, and provides code snippets and how to modify them to correct for errors.


Thanks so much for helping out Presto! Sincerely appreciate the links.

I’m using Unreal’s own Automotive Materials pack so I’m kinda surprised the Glass from the pack is having this issue and makes me think it’s something in my PPV. I will read through these links very carefully and thanks for taking the time to help me out!