Apply static bump map to normals in Blender 2.82

Question

I'm new to Blender and graphics. I'm trying to apply a bump map to a mesh and export it in OBJ format, but I have two problems:

1. The .obj file nor the .mtl file contains any information about the bump map, in fact by reimporting the obj in blender the mesh doesn't have any bump mapping applied. By looking into the obj, normals are just very slightly modified and there's no map_Bump entry in the mtl either.

2. If I undestood well the bump map needs to be computed and applied each time the mesh is imported in a software, using the bump image. Is there a way to apply "statically" the bump map to the normals, so that the normals are modified just once using the bump image and saved with the mesh? So that I do not need to keep the image and recompute the bump map each time.

Thanks.

Answer 1

1. OBJ exporter is very basic. It's a format optimized for readability and compatibility. I don't think the Blender exporter checks for bump maps, it's fairly basic. In my test it did look for the diffuse map, but it mapped it like this: (inside the .mtl file) map_Kd G:\Libraries\Textures\CIMG2124.JPG So if we copied it to your machine, the link would break. If at all possible, use .fbx, it's more versatile and better maintained.
   
2. Bump maps can't be "applied", every ray hitting your surface will take the normal map into account, meaning calculating its effects in realtime. The trick is to add detail without geometry. To bake the bump map, to your mesh (the opposite of what bump maps are for) you'd have to add tons of vertices. It does not modify the normals, it adds to the direction of the ray that's being reflected, depending on the pixel's color.