While the face normals (the one from a center of each triangle ) looks perfectly up those normal are derivative as a median of vertex normals in triangles corners. The bottom left corner for example , clearly not 90 degree up . it's what creates shading gradients. Face weighting, or direct normals editing could fix it .…
@Alex_J I wonder how well this works in practice. Losing GI in a scene originally designed and lit for it would have a very significant impact visually, I feel like you'd need 2 different lighting scenarios for lumen on and lumen off. I almost feel that I wouldn't even bother with trying to support both. Unreals current…