Hi, I've been trying to add my own wheels and I keep running into this problem no matter what I do. I get the 3d model, I bake the normals for it, do a specular and a diffuse map and when all is said and done, the wheel will change lighting at every 180 degree turn. Turns dark, then turns light, then dark again and so on. I kept reading up on normal maps and so I would kind of understand that if my light was at an angle when baking my normal the wheel could legitimately do that. I work in Blender and I moved my light at 0 angle "track to constraint" facing the rim. I also rotated the rim so that I would bake from above on the z axle. It still kept doing the same, when done. (and yes I restarted the game and cleared the cache each time). Then I tried baking with the light at 0, 0, 0 coordinates, and it didn't make any difference to the normals. Then I tried to select the right side of the normal map and copied and flipped on to the other side. But it was doing the same flashing thing, which I don't understand. How is that possible, if the normal is completely symmetrical? So then I did something else. I baked a normal for 1 spoke only and radially copied it 5 times at 72 degree angles offset in GIMP. Then I added that normal map and it kept doing the same flashing thing at every 180 degree turn, which utterly and completely baffles me. How do I bake a normal map that is radially symmetrical?
In your materials.cs do you have [0], [1] or more? What is going on looks like similar to what I had and solution was to remove lines so that there was only [0] for textures, however I don't understand materials.cs quite well and you probably know about such better, just a thought that occured if you haven't tested changing materials.cs on that part yet.
I used the original materials.cs in the sense, that I had the first layer( with index [0]) with the freshly baked normal map and null.dds and null.dds respectively for specular and diffuse( I think this in practice gives the reflective metal effect on surfaces) then for second layer I had normal, specular, and diffuse. I'll give your method a try anyway. It can't make things any worse.
Here is thread about my issue, maybe you get some ideas based on that: https://www.beamng.com/threads/material-shading-issue.51762/
