Translucency/Refraction issues with Glass RT shader in 4.25

Development Asset Creation
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Hi everyone. I’m experimenting with UE4.25 at the moment. Trying to follow this webinar:


Using the Automotive Materials pack along with the Automotive Beach Scene. I’m getting a fairly nice result, but do have an issue with the glass for the headlights. I’m using Raytracing in the scene, so I assume for a physically correct result I should be using the shaders in the Glass_RT folder.

They work as expected (I think) with non-metallic materials behind them, such as car paint or a generic lambert, but the moment I assign a metallic material like chrome or brass, suddenly the refraction fails and refracted object appears black.

With regular Glass material (not the RT) it seems not not have that issue. I tried having single sided mesh and double sided mesh, changed the specular and opacity sliders, made the material double sided or single sided. Effectively I can’t get it to look correct. On the UE documentation I can’t find a section specifically for headlights. On the windows of the car it seems to work okay, but then again there aren’t metals inside. What is it that I’m missing here? In the webinar above the glass on headlights looks really nice.

I’m attaching a screenshot of my issues.

316791-rt-glass.jpg
316791-rt-glass.jpg904×665 131 KB

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From what I’m able to find online (which isn’t a lot) I don’t think raytracing is currently working properly with translucency even though when Epic shows it in their videos working fine. No one has answered my question on here about it so doubt we’ll get a work around or explanation.

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Hey I actually found a solution to my specific issue with the Automotive RT materials. In fact Daryl goes over it in the video I’ve linked above towards the middle/end part. There’s a switch/override on Automotive material pack, that basically affects what they refract. It’s done in order to optimize the speed of the scene. You can turn it off and it solves this issue.

I had a look at your thread, not sure what causes your issue. I’ll try and recreate on my end and see if it does the same

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I’ve watched that video a few times, and the switching I think you mean is to do with reflections not translucency. I could be wrong but from watching that I don’t think that’s the answer. I hope I’m wrong though lol.