Subject: Re: Poly goes poof. Film at 11.
From: Allen D Hastings <[email-masked]>
To: [email-masked]
Date: Thu, 25 Aug 1994 16:18:10 -0700

>THE PUZZLE: Why does the polygon render in frame 1, but not in frame 0?
> 
>No, the camera isn't moving "behind" the poly -- it's only moving two
>centimeters, after all. Strangely enough, if your turn on double-
>sided, the poly goes dark... as if you are indeed looking at the back
>side of the poly. But you're still looking at the front.
 
I have to admit I was skeptical when I first read your message, but
then I tried it and you're absolutely right!  LightWave was erroneously
culling the polygon, thinking it was a back face when it wasn't.  This
was caused by a subtle error in calculating the center of the polygon,
an error which has existed in LightWave since 1.0 but which so rarely
causes any noticeable effects that it wasn't discovered until now.  Of
course I've fixed it now that I know about it, so the fix will be in
4.0.  A workaround for 3.5 might be to subdivide the triangle.

- AH