I was trying to figure out why there were shading artifacts on a 3D object I created for some vision experiments.

I’ve got a metric-ton of Mathematica I’ve written over the years for doing computational geometry and it stood me in good stead. The blue ‘V’s you see are mismatched surface normals – they should be coincident (e.g. exactly the same) but, as you can see, there is a systematic error. Fixed it.