Hey y’all: so I feel like I’m maybe missing a check-box somewhere…? I’m wondering how people use custom vertex normals with two-sided materials, since by default it flips the backside normal. Ergo, if you’re projecting the normals from a flat plane or sphere or whatever onto your grass (a pretty common practice), the backsides will light upside-down. Is there a way to get it to not flip the normals on the backside of the material?
One (kind of ■■■■■■) work-around I was playing with, was to just use world-space normals instead of tangent space. Works ok: you can just convert your tangent space normals into world at the very end, but it seems to mess up normal combination, plus I can envision plenty of scenarios where artists might want a more nuanced base direction than just going straight up in world space.
images attached: custom-projected vertex normals in Maya, and how they’re interpreted on a two-sided material in the Unreal world space normal buffer.