In order to perform tangent space directional diffuse bump mapping, I have to compute, for each texel, the direction from this texel to the light, in tangent space, and then dot it with the corresponding texel from the bump map.
The direction, in object space, from each texel to the light is the same. However, in tangent space it has to be interpolated (using a cube map, or simple gouraud interpolation) with the 3 vertex of the texel’s face.
I’m having trouble with this, because I have a rather coarse geometry, and it leads to artifacts when using the Gouraud interpolation. A solution is to use a cube map to normalize … but I have no more texture units available. (Decal, detail, diffuse cube map, bump map)
Would it be possible to avoid such artifacts by computing my normal map in object space, rather than in tangent space ?