Kartoffel answers perfectly.
Haha - did the "hit" part escape you? Go to c_trace in the manual. There you'll find the link to the "hit" struc that holds even more cool data after a trace.
The concept of nx is the a Normal. A Normal unit vector is common in all 3D. It would truly be amazing if you have been working with 3D for so long and have no idea what a Normal are.
Here is your reading https://en.m.wikipedia.org/wiki/Normal_(geometry)
Thanks for the sprinkling of condescension in your tone. I saw that one coming. I knew you couldn't reasonably be that chipper. ;-)
However, as long as I have been doing this, this is a part-time gig for me, as I have my full time bread and butter job. Got to keep a roof over my head. :-)
You are right, though. I should have linked it to the hit variable, and looked that one up. Learned a lesson. Thank you for the advice on what a Normal is.
