Still helping Fluent get their converter to OpenDX worked out and encountered a strange phenomenon. Any insightful comments welcome:
They were supplying me with test sets made up of tetrahedra, that I was visualizing in DX. I used "front colors" and "back colors" and normal glyphs to check for the correctness of tet winding. In a test case, I had 1 cube cut into 6 tets: 4 were wound correctly (front colors were out and normals started on face surfaces and projected out) and 2 incorrectly (back colors showed and normals went through the interior of the tet volume). Trying to simplify things for debugging, I modified the .dx file to figure out which 2 were the bad boys so I could study their connection list order. Lo and behold, by eliminating (commenting out) all the "good" tets, the previously "bad" tets became good (some sort of epiphany, I guess, or maybe a relativistic moral upbringing). Turns out that DX decides which way your tets are wound (ouch!) depends on which one it sees first in the input list. That is, if I now add back in one of the "good" tets to the list but position it AFTER one of the "bad" tets, the "bad" one is good and the "good" one is bad. Aiie!! The documentation clearly implies that one of the (2) correct ways to wind a tet is to traverse the first face COUNTERclockwise, then go BACK to pick up the 4th vertex. My description of a "good" tet follows this convention, and in my worldview a "bad" tet traverses the first face CLOCKwise, then goes BACK to 4. But now my faith is shaken. Any apologists out there to counter my apostasy? Chris Pelkie Vice President/Scientific Visualization Producer Conceptual Reality Presentations, Inc. 30 West Meadow Drive Ithaca, NY 14850 [EMAIL PROTECTED]
