Lumen Reflections look incorrect on stacked Translucent Materials

[leoviale]

Hi, I’m running into an issue with Lumen Reflections on translucent objects (like glass), especially when multiple layers of the same material are stacked. It seems like when the shader overlaps onto itself, it falls back to something like a sphere reflection capture, and the result looks quite bad.

In previous versions, I was able to avoid this effect by using the r.Lumen.TranslucencyReflections.FrontLayer.Allow cvar. It used to prevent the material from rendering behind the overlapping mesh, but that no longer seems to work. Now, I’m getting this reflection on all overlapping surfaces, which is exactly what I’m trying to avoid:

From what I can tell, the fallback reflection is being controlled by the r.Lumen.TranslucencyReflections.ReprojectionRadiusScale cvar. I set it to 0.1 to better illustrate the issue:

Is there any way to correctly render materials behind translucent ones, or disable this fallback behavior when surfaces overlap?

Thanks!

[BananableOffense]

I can’t test this right now but I think if you enable “Order Independent Transparency” in the project settings it fixes this. You may also need to enable High Quality Translucent Reflections of you haven’t already.

Worst case scenario you can draw the overlapping section of glass to a custom depth stencil so and mask out the second pane of glass.

[Arkiras]

When using Lumen reflections, only the first translucent surface can have high quality reflections. To my knowledge there is no way to improve this.

[BananableOffense]

You could also try using dithering to alternate the visibility of the layers each frame. Then the TAA can accumulate reflection data for multi layered glass over time. This will make the glass even more translucent though, so you’ll probably need to boost the opacity and specularity to compensate.