Hi there,
Im playing around with some raytracing in 4.25 and cant seem to get translucent materials to correctly appear in reflections.
I read, that RT Reflections don`t reflect actual GI, only direct light. Is that correct?
But is there any way to make that glass vase appear in the mirror? Or is that just not possible at the moment?
You have ticked “include translucent objects” in the reflection section I guess?
I’m having similar problems. They either don’t show up or they are black even with 12 bounces. There is a chapter in the documentation how to set up refraction in glass but whatever I set as refraction value in either specular or refraction never seems to change anything.
I turned that feature off and it looks quite good to me with raster translucency instead of ray traced glass. Reflection on the glass still seems to be ray traced.
Yes, that`s on. Also tried higher bounces and samples, but that doesnt solve the problem.
Using raster translucency with ray traced reflections doesnt change how the glas looks in the mirror reflection…
Could it be sort priority for translucency? even in the case of raster translucency since it is combined with RT reflections…
16 bounces is a ton…does it slow down for that number of bounces?
8 refractions is rather large as well…tried reducing each of those settings to 2-4?
Actually check it in run time. Sometimes it only works proper when you play the game and not in the editor.
I have a curtain in the scene as well which is part translucent. It doesn’t work well either so it’s not just the glass.
Tried sort priority, that doesnt change it.
Yeah, 16 and 8 is more than enough, but I was kind of frustrated and just cranked it up 
I think it`s raytraced tranclucency in general? Run time doestn help, but thanks for the suggestion.
I switched to path tracer as a workaround for the reflections. Works in this case, where I dont really care about performance, since its for a cinematic, but that can`t be the only way to get translucent objects to show in reflections, can it?
Thanks for the suggestions, I`d gladly try out some more!
There might be a few youtube videos covering more in-depth techniques to get accurate reflections of translucency.
I`ve been looking for days now and found a lot of videos explaining raytraced reflection/refraction. But none that covers RT translucency in reflections.
I found another post here on the forum, that seems to have the same problem:
https://forums.unrealengine.com/development-discussion/rendering/1777072-transparency-in-raytraced-reflections
I see. I think it may be there’s no normal for the reflective glass material. There needs to be a normal for translucency volumes, so try connecting a normal texture (even a flat texture with little to no variation) to the Normal pin in the glass material. How about a screenshot of the current material graph? It might help in getting more applicable help.
Youre right, there was no normal for the material, but it doesnt help, I just tried adding a simple one.
The material is pretty simple, here`s a screenshot of the glass material with a normal map applied:
I notice it’s set to Surface Forward Shading. This entails no support for a number of deferred shading features since it uses the Forward Renderer. Try setting the material to Surface Translucency Volume, which is basically the same but doesn’t use the Forward Renderer, yet instead the Deferred. If it doesn’t work, try Volumetric Per-Vertex Directional (which is based on vertices and takes Normal into account).
I’m testing the glass material I put together based on the doc instructions, and only slightly modified by placing a vector4 into the Normal input (0.8, 0.8, 0.8, 1). It may work to use a Fresnel node plugged into the Refraction pin too. Here’s a picture of the material graph I’m using, which shows a reflection in a metallic surface (M_Metal_Chrome from Starter > Materials), though has some aliasing (which I’ve read is due to other factors). The problem could also be with the mirror material.
Fresnel values are default.
](filedata/fetch?id=1785756&d=1594225668)Thanks presto, but sadly that didnt help. I set up the material exactly like you suggested (well, almost. I tried the vector4, looked kinda weird. Im using a flat normal) and also tried Volumetric Per-Vertex Directional. Still not showing up in the reflections.
Do you have raytracing turned on in your example scene? Because I think thats the problem. The glass material from the doc is not for raytracing, the refraction pin doesnt do anything with RT. I did try the RT Glas from the Automotive Material Collection though. With no luck, the problem persists.
Thank you for your help! 
Did you try plugging the fresnel lerp in Specular instead of Refraction? I read in the doc just now that Specular drives IOR in ray-traced reflections / translucency.
Are screen space reflections set to “0” in the post process volume (PPV) there? Is there more than one PPV in the scene? If the settings are different among multiple PPVs, and priority isn’t set correctly, then it could be preventing the translucent glass materials from rendering in reflections.
A few project settings to change for reflections are:
GBuffer format - set to High Precision Normals
In the LOD0 settings for each object involved in the reflections, enable “High Precision Tangent Basis” and click Apply.
Here’s a link to a reflection article. And remember, UE4 uses a hybrid ray-traced / raster system, so it is going to be a combination of raster methods and the ray-tracing settings in the PPV and meshes / lights. For example, in the doc, a reflection capture is placed as a fallback to remove the black artifacts in inter-reflection (which is what a translucent glass reflecting in a mirror is). The article also instructs to do the same thing to get rid of the black (looks like it’s not rendering) artifacts, in addition to proper lighting.
