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Transluscent surface insanely bright after building lighting.

Development Discussion Rendering
#1

I have a simple plane that has a broken window texture across it, and uses a translucent material. The problem I have, is when I build the lighting, these surfaces are insanely bright compared to their surroundings.

I have light mass coordinates set-up on the place (it’s part of a larger surrounding mesh as well), and also have two-sided lighting and two-sided material checked in the material editor/details panel. Do translucent surfaces not have lightmass textures baked over the top of them? The issue was never present in UE3, which applied shadowing just like a multiply layer on top as far as I know.

The material network is pretty simple. I also tried creating a two-sided plane in 3DS Max with separate lightmass UV’s, but still to no avail. I did just find this on the UE4 Documentation though, but I am using stationary lights.

So… any clues?

#2

Yes, I am afraid that static shadows currently do not affect translucency. Trust me us in house developers bring up this issue often :slight_smile: I know it is “planned” but I cannot say how much longer it might be since I don’t know.

For now, I can tell you that it is possible to capture the lighting manually and apply it manually as a texture inside the material. I have had to do it a few times. Basically you set the material to be a white opaque material and then rebuild, take a lighting only screenshot and import that with sRGB unchecked. If its a mesh more complex than a simple window pane, you can actually unwrap a mesh usinga vertex shader by using an unwrap material function. There is one somewhere in engine. 4.3 will have a BP powered tool for unwraping meshes so that you can do custom baking operations more easily.

If the lighting on the mesh is fairly flat, I would just correct for it using a material instance. Sorry I know that is probably not the suggestion you were hoping for.

#3

Ah I had a feeling that might be the case… that’ll have to be the current workaround then!

#4

There is one case where this actually works, in the ES2 mobile rendering preview you can actually see correct lightmaps on simple translucency.

#5

The mystery deepens!