UE 5.2.1 City Sample Vehicles Wrong Windows Transparent Reflections Shading


As showcased in the above screenshot I am currently having an issue with the way how the vehicle windows material is being shaded for the “City Sample” in “Unreal Engine 5.2.1 Source Built”.

The windows of all vehicles have no reflection whatsoever and are just a dark tinted transparent shading looking very unrealistic and wrong compared to the shading of the rest of the scene…

Does anyone know what causes this and how to fix it ?

While I didn’t read too much into it, Epic tweaked how their transparent reflections system works for the city sample by a fair bit. They wanted SSR in addition to their rough lumen reflections (which were the only option at the time), and it’s resulted in a transparency handling that’s somewhat nontraditional compared to the engine default.

What does this mean?

Epic edited Unreal engine’s normal reflections handling for the matrix demo, so it’s acting differently in ways that I don’t understand.

The demo was made with an early version of UE5, 5.1 added High Quality Translucency Reflections which has a proper implementation for the reflections they hacked into the engine for the demo, but since that didn’t exist in 5.0, you manually have to turn it on and check a few boxes for it to work.

Epic typically doesn’t revisit these older sample projects, beyond making sure they at least work. Some features get added to the engine, some features get deprecated. Using the engine version it released on usually has the best chance of everything working properly, but newer versions have more and better features that can be enabled and typically have better performance.

Better performance is especially true for the matrix demo. Between 5.0 and 5.2, they made a lot of optimizations and improvements to surface cache coverage, HWRT tracing memory and compute efficiency, and more.

Do you know how they hacked in their reflections for the matrix demo?

On a closer inspection of the vehicles’ glass material in use, I noticed that if I change the values from “1.0” to “0.0” on this specific Material “M_Veh_GlassThin” (a material from which all further Vehicle Glass materials seem to inherit parameters) it solves the wrong/missing shading and renders the glass materials for all vehicles (within the City Sample project) as expected…


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