Since I’m using a world-space normal map, I was able to remove the seams by switching to a paralell light. That reduces the irradiance pass to a screen-space quad which takes advantage of extra information available outside the mesh (in uv space) which was initially intended to avoid mip-mapping issues.

The diffuse texture should probably be redone at this point. Actually, both the model and textures could use extra work to take real advantage of the shader. Slightly more tesselation on the mesh and more detail in both normal and diffuse textures.

The stretching method described in the book requires a certain amount of tesselation due to the use of partial derivatives; big polygons in uv space can cause discontinuities. My test model is not very dense so I’m still trying to figure out a way of doing it efficiently.