Quote -
For a triangle ABC what this code does is;
N = ABxAC + BCxBA + CAxCB  removing all the terms that cancels itself.

Yes, thanks! I kind of knew that formula, which you might have guessed from the fact that I just implemented it. What I didn't know is how you got from there to the code you posted. I think I've figured it out now (and I'm happy to post the derivation later tonight if anyone's interested), but a reference would still be nice if you happen to have one.

On the way, I came to understand another formula for the face normal that I've seen floating around (and used in code because I got it from a trustworthy source; but now I've forgotten what that source was ) and could never quite make sense of. So that means I can probably shave of another Numeric operation from the code. I don't think I will use kawecki's version, since it looks a bit too convoluted for my meager Numeric skills.

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