Path: utzoo!attcan!uunet!bu.edu!orc!decwrl!sdd.hp.com!hplabs!hpfcso!hpfcdj!kuba
From: kuba@hpfcdj.HP.COM (Kathy Kuba)
Newsgroups: comp.sys.sgi
Subject: GL Lighting POSITION
Message-ID: <17450005@hpfcdj.HP.COM>
Date: 4 Sep 90 19:00:13 GMT
Organization: Hewlett Packard -- Fort Collins, CO
Lines: 16

I recently received my SGI 210GTX workstation (running 3.3) and began
porting code from my 120GTX (3.2).  All went well, except that my light
sources did not illuminate my objects.  Upon further investigation, I
discovered that moving my POSITION from 0 0 1 0 to 0 0 -1 0 fixed the
problem.  Has any one else seen this??  I really don't want to do keep
different versions of code for each machine.  The SGI Hotline graphics
expert I talked with said they "fixed" the light sources so backface
lighting would work properly.  All other SGI graphics workstations I've 
used have the positive z axis pointing out of the screen, so a light
at 0 0 1 0 is  shining from behind to the origin.  If they believe this
is really a "fix", then why didn't they make it transparent to the user?  
The answer I received, "change your code", is not acceptable.  Comments 
suggestions, and alternate solutions welcome!


Kathy