Hi, this has caused me grief in the past and I have been using a python
version of AngleBetweenVecs.
Just now I found the problem. when AngleBetweenVecs compares 2 vectors
that are the same, it can return nan, nan being a float type.
nothing is equal to nan except float('nan').
Shold be changed to return 0 instead of nan?\
-Cam