This may be a bug, or just me not knowing what the h*ll I'm doing. I can't seems to find a fix though.
I was trying to wrap a car in mud, using a combined model of all the underlying parts with a mud splatter texture on it, and kept getting "black" spots in weird places. After some fiddling, I saw that they were mirrored verions of the wrapped texture. After some more fiddling, I found out that the spots were actually the reflections of the mud layer, only mirrored.
I re-created the issue on a simpler setup. See the attached image for reference.
It's a plane with a simple carpaint material on it, and an instanced plane on top. The instanced plane has a material with displaced lines. The texture I use for displacing the lines is also used as an opacity map. The texture is applied using a triplanar map.
Notice the reflections of the lines on the carpaint. They're mirrored! Using a blendedboxmap produces the same result. A typical plane UVW map does not. Excluding the plane from reflections also cleares the problem, but that's not a usable option.
Any ideas?
