[comp.sys.sgi] Another SGI graphics problem/solution to last one

cycy@isl1.ri.cmu.edu (Scum) (12/08/89)

First, I should, since I posted the question here, answer why my system
wasn't working when we got our upgrade. It turns out that, unbeknownst to
me, we only got the eoe and nfs upgrades; we didn't get the development
package. Thanks to the SGI people who responded to me. I really appreciate the
fact that you folks read this board and try to help us with the problems here.
Now, my system is a happy system once again, and running fine.

Or at least it was until a new feature was added.

We want to use dgl (Distributed Graphics Library) and have things appear
on another monitor's screen. That works; however, on the local screen there
is a problem with lighting in one of the windows, and it's pretty weird. The
objects appear, and they appear in the correct material colour. However, the
lighting model or the lights seem to be screwed up. The objects are just
coloured flat now. No shadows, no shading, no perspective, nothing. This worked
in gl, but it seems there is something missing in dgl. By the way, normals are
set. I tried depth cueing and z-buffering  with dgl on the local, remote and
both screens, and those worked. The lighting works when I link gl, but not dgl.
Of course, the graphics don't get distributed in gl. I called the graphics
hotline (in fact, they're the ones who suggested these tests), and they're
working on the problem.  However, given as I'm desparate for time, I thought
I'd post on here to see if anybody had any clues on this problem. Perhaps
somebody has encountered it before, for instance.

Thanks for any help.

						-- Chris.
-- 
					-- Chris. (cycy@isl1.ri.cmu.edu)
"People make me pro-nuclear." -- Margarette Smith

tarolli@riva.esd.sgi.com (Gary Tarolli) (12/08/89)

From postnews Thu Dec  7 15:18:37 1989

In article <7254@pt.cs.cmu.edu>, cycy@isl1.ri.cmu.edu (Scum) writes:
> 
> We want to use dgl (Distributed Graphics Library) and have things appear
> on another monitor's screen. That works; however, on the local screen there
> is a problem with lighting in one of the windows, and it's pretty weird. The
> objects appear, and they appear in the correct material colour. However, the
> lighting model or the lights seem to be screwed up. The objects are just
> coloured flat now. No shadows, no shading, no perspective, nothing. This worked
> in gl, but it seems there is something missing in dgl. By the way, normals are
> set. I tried depth cueing and z-buffering  with dgl on the local, remote and
> both screens, and those worked. The lighting works when I link gl, but not dgl.

I think you stumbled across one of the commands that behave slightly differentlyin the GL than in the DGL.  The command is lmdef, and the GL ignores the third
parameter whereas the DGL requires it. People normally, by habit, put 0 as 
the 3rd parameter and the GL works fine.  If you read the man page , the 3rd
parameter is supposed to be the number of floats in the 4th argument.  The
DGL looks at this value to determine how many floats to send.  Thus if you
are like most people and set it to 0, the DGL will send 0 floats and thus
lmdef wont work and the result will be just like what you are experiencing -
total weirdness.

There is also a slight difference in behavior if you use NULL for the 4th
parameter and dont specify 0 for the 3rd.  I dont suspect this is your 
problem, however.

Check the 3rd parameter and make sure it is set correctly, that should fix
your problem.


--
						Gary Tarolli

cycy@isl1.ri.cmu.edu (Scum) (12/08/89)

In article <45948@sgi.sgi.com>, tarolli@riva.esd.sgi.com (Gary Tarolli) writes:
> In article <7254@pt.cs.cmu.edu>, cycy@isl1.ri.cmu.edu (Scum) writes:
> > We want to use dgl (Distributed Graphics Library) and have things appear
> > on another monitor's screen. That works; however, on the local screen there
> > is a problem with lighting in one of the windows, and it's pretty weird. The
> > objects appear, and they appear in the correct material colour. However, the
> > lighting model or the lights seem to be screwed up. The objects are just
> > coloured flat now. No shadows, no shading, no perspective, nothing. This worked
> > in gl, but it seems there is something missing in dgl. By the way, normals are
> 
> I think you stumbled across one of the commands that behave slightly differentlyin the GL than in the DGL.  The command is lmdef, and the GL ignores the third
> parameter whereas the DGL requires it. People normally, by habit, put 0 as 
> the 3rd parameter and the GL works fine.  If you read the man page , the 3rd
> parameter is supposed to be the number of floats in the 4th argument.  The
> DGL looks at this value to determine how many floats to send.  Thus if you
> are like most people and set it to 0, the DGL will send 0 floats and thus

> Check the 3rd parameter and make sure it is set correctly, that should fix
> your problem.
> 						Gary Tarolli

That was it! Actually, I had miscounted the parameters (I skipped a line in
when I was counting the elements in the array) and had used 10 instead of 14
for the third parameter. Thanks a million!!!!!!!!!

					-- Chris.
















-- 
					-- Chris. (cycy@isl1.ri.cmu.edu)
"People make me pro-nuclear." -- Margarette Smith