Path: utzoo!news-server.csri.toronto.edu!rutgers!ucsd!ucbvax!LISBOA.KS.UIUC.EDU!nieswand
From: nieswand@LISBOA.KS.UIUC.EDU (Benno Nieswand)
Newsgroups: comp.sys.sgi
Subject: Re: Personal Iris lighting problems
Message-ID: <9103142310.AA04032@.lisboa.ks.uiuc.edu.>
Date: 14 Mar 91 23:10:26 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 27

Robert Ringrose writes:

> It works fine until I put in a call to a routine with the
> following code, part of an attempt to get the current
> projection and modelview matrices:
>
>
> mmode(MPROJECTION);
> mmode(MVIEWING);


I had similar problems and I worked on it for a long time. It's a  
while ago and I don't remember all the details but I discussed the  
problem with several people and tried almost every possibility to  
figure out the systematics behind the problem.
 I wanted to bind a light to the world coord frame and change  
projection and viewing. So I did mmode( MPERSPECTIVE) and change  
perspective() AND polarview() without changing the light binding  
then I did mmode(MVIEWING) again. This worked fine, as long as I  
didn't switch the light off and tried to rebind it. The new source  
direction(infinite far away, as supposed) was dependend on the last  
projection matrix before the rebind, in contrary to a determined  
relativ position to the world coord frame. I'm sure there is a bug.  
Another time I had the same problem Robert, so the source rotated.

If there is any solution, please let me know.
           Benno Nieswand