And we're down to 26 seconds at the end of this optimization day. I had some trouble speeding up the OBJ parsing code at first, but then I took ADP's advice seriously and wrote a custom function that ignores all the parts I don't need. It's also quite short, as a by-product of less Python code in a tight loop generally translating to faster execution times.

-- I'm not mad at you, just Westphalian.