Download

Path traced glass missing reflections

Can any render experts explain why I am not seeing any Ray Traced reflections in the car windshield (using Path Tracing)?
For comparison also a screen grab of precomputed or baked.
I have enabled Ray Tracing for Reflections in my PPV and set number of bounces to 4.
But even when I switch Reflection Type to Screen Space I am not seeing any reflections in the car windshield. In particular the overhead softbox (emissive light).
Puzzling.



PostProcess

What are your path tracer settings in the PPV? It has its own settings, e.g. # of bounces. I may be wrong but I don’t think the other raytracing settings effect the pathtracer. Also good to see your glass material.

Thanks for the feedback. I also tried creating a bare bones simple glass material based on William Faucher’s path tracing tutorial but no difference.
PPV_Pathtracing

I removed the background and moved the color checker to make the difference more obvious


I’ve been working with the pathtracer a bit, but I haven’t run into this problem. I would try not making the opacity 0, and also adding a non-zero value for metallic. In my experience it seems like for the pathtracer metallic controls the level of reflectivity. All my glass materials are to some degree metallic… other than that, I don’t see anything that stands out as a likely culprit. But notice that you have a similar issue with the logo and trim around the grill. Might be the same issue in that material?

1 Like

Are you using UE 4.26 or UE 4.27? Because the Pathtracer got some major updates in 4.27, and support several features, that are still missing in 4.26. And how the pathtracer handled glass was one of the big changes.
So if you are in 4.26, convert your scene to 4.27 (simply start 4.27 and try to start any 4.26 or lower scene, it will ask you to create a copy for 4.27), and see, if that changes something.

Also, as already mentioned, the pathtracer has it´s very own settings, the raytracing settings do nothing for the pathtracer :slight_smile:

Edit: a quick testscene with your shown glass material in 4.27:

Thanks guys. Will try suggestions. Yes using 4.27!

Something seems to be off, because if i try to render a car with your simple glass material, then the windshield becomes black and reflective (not very strong, but it reflects emissive stuff quite well), while the covers for the lights are transparent. I guess, it have something to do with how the windshield is modelled, haven´t checked, if it´s just a simple polygon plane, or an actual body with some thickness, to let the pathtracer properly work.

And your Audo logo at the front should stay reflective too, it should not become such a bland grey mass.

Ok, i looked into my model, and the windshield and other windows were indeed just simple polygon planes, not meshes with some thickness. So i extruded the windshield to give it some mass, and yeah, the path tracer liked that a lot better than the version, that was basically just a plane with zero thickness. With that change, the windshield became transparent and reflective, just as you would expect it to be.
So i guess, you should check your windows meshes too :slight_smile:

Sidenote: Give your simple glass material a parameter for metallic too, set this to 1, and set the color to white (or any other bright color). With that, you can create colored glass, if you play with the opacity ->make it less transparent. With metallic 1 and white as color, it will act like one of those reflective sunglasses, if it is not perfectly clear ^.^
Remember, metallic materials need a color input greater than zero to be able to reflect something, white for a chromelike material.

Thanks for the feedback.
I tried again with the Simple Glass material and for some reason it works now. Although still puzzled why the Audi logo is not rendering as chrome.



Is there anything fancy in that chrome material for that Audi Logo?? Stays it that way, if you replace the current material with a simple chrome material? ( color white, metallic 1, roughness 0. nothing else)
From the looks of it, it seems, that its roughness might be set to 1 or white (completely rough), instead of zero (shiny).

And it seems, you got working curved screens in the background ^.^

Thanks. Yes the chrome material for the configurator demo was too complex or something. Created a simple chrome material and it works.

The default Master Material is a bit much. Might have better luck using one of the automotive materials from the marketplace.

Yeah, this looks like a little bit overkill for a chome material ^.^ With the automotive materials from the marketplace, there is a pack from Epic, however, a fair word of warning: Some of the included materials are really broken with raytracing (not so sure about path tracing, had never tested it before) in newer versions of Unreal Engine - especially the included glass materials created some really weird and broken stuff (you should find some threads about that in the forum).

This is the pack i am talking about: Automotive Materials in Epic Content - UE Marketplace