Generation of mesh normals and the raytracer is on GitHub!

How did you implement this? I tried, but my generated normals look really odd.

What I did:
1. During OBJ parsing, build a list VN of all vertices V with an associated empty normal vector.
2. For each face F from the OBJ file, generate standard triangle shapes via fan triangulation, this also computes the triangle normals N as described in the book.
3. For each vertex A, B, C of the current triangle, add N to the normal vector of the respective vertex in VN. Keep count of the number of triangles that share this point.
4. Divide all normal vectors in VN by the number of the triangles shared by this point.
5. Generate smooth triangle shapes for all faces by using the vertex normals from VN.

I also found this explanation, which is very similar to my approach:
www.iquilezles.org/www/articles/normals/normals.htm

The author skips the division in step 4, since scalar division only reduces the vector length and the vectors are normalized anyway.

However, something doesn't work out...

EDIT: I also took a look at your code, but (ignoring my lack of knowledge concerning Go), I don't see any major differences.