From: Angus Dorbie (dorbie++at++sgi.com)
Date: 03/15/2000 10:54:58
Mark Wear wrote:
>
> On a previous query, I got the response:
> > "Each pipe should do this in a draw callback and it will just work. The
> > pipes and contexts have separate state information, the draw processes
> > and callbacks will operate on the current context on each pipe. "
>
I wrote the above, it has nothing to do with color maps. It applies to
the color table extension. It is completely valid :-) As I have already
said, the only way to do this is to make the OpenGL call in each draw
process around the color tabled object. It will not be saved with the
texture object.
> The glColorTableSGI extension is not the same as the maps discussed in the
> OpenGL Programming Guide, so I'm not sure the above statements are valid. As
> I understand it, the color tables provided by the color table extension
> allow you to adjust image contrast and brightness after each stage of the
> pixel processing pipeline depending upon which target you specify. If you
> specify GL_TEXTURE_COLOR_TABLE_SGI as the target, you have also selected
> where in the pipeline the mapping will occur. Depending on where along the
> pipeline this actually gets done, it may only be possible to implement a
> single GL_TEXTURE_COLOR_TABLE_SGI mapping per system. ...Or, I could be
> wrong.
Depends what you mean by system, if you have completely different draw
processes, making one call in a different process won't affect the state
in the graphics context of another process.
In addition like I said above the color table is not part of the texture
object so you would be required to enable and disable the look up and
keep the drawing of the color table contiguous perhaps using draw bins
to do this.
Cheers,ANgus.
>
> A good test would be to load a model with Perfly on one pipe and start your
> application on the other. If the textures within Perfly exhibit the problem,
> then you have your answer. If not, you need to look further into your
> contexts.
>
> ...Or, You could load the models with intensity textures and then not
> disable the LUT at all, allowing the models to be colored by the LUT.
>
> Good luck.
>
> Mark Wear
> Multigen-Paradigm Inc.
> mwear++at++paradigmsim.com
> http://www.multigen-paradigm.com
> phone: 972-960-2301 fax: 972-960-2303
>
> -----Original Message-----
> From: christopher.g.dorosky++at++lmco.com
> [mailto:christopher.g.dorosky++at++lmco.com]
> Sent: Wednesday, March 15, 2000 10:10 AM
> To: info-performer++at++sgi.com
> Subject: Color lookup tables on multiple pipes.
>
> Sorry for the repeat post, but I am still having trouble.
>
> In my scene, there is a terrain node which has all of the terrain data.
> There are also various 3D models.
> The source data for the terrain is greyscale. The source for the models is
> color.
> I can apply a color LUT to the terrain data, and get good results. I do not
> want to apply the LUT to the models, because colorizing a color model has
> bad results.
>
> A solution, on a single pipe system, is to set up a color-LUT, and
> selectively enable and disable it.
>
> Since all terrain is under one node, applying a pre-draw and post-draw
> callback that glEnables and glDisables GL_TEXTURE_COLOR_TABLE_SGI works
> fine. The idea is that before terrain is drawn, the table is turned on, and
> when terrain is done, the LUT is turned off. This works great on a one pipe
> system.
>
> On a two pipe system, I have not figured out how to make the system
> understand the pipe context for the LUT's.
>
> On a previous query, I got the response: "
> > Each pipe should do this in a draw callback and it will just work. The
> > pipes and contexts have separate state information, the draw processes
> > and callbacks will operate on the current context on each pipe. "
> >
> However, what I see when running on two pipes, is intermittent color-to-grey
> flashing of the terrain.
> The pre and post draw callbacks appear to be running on both pipes.
> If I place
> if (!glIsEnabled(GL_TEXTURE_COLOR_TABLE_SGI)) { printf("table was already
> off!!\n"); fflush(stdout); }
> in the post draw callback, I get printouts at each flash (can happen several
> times a second, but usually once every several seconds).
>
> I have not successfully told the two pipes how to use or not use the LUT
> without shutting it off for the other pipe.
>
> Has anybody else run into this?
>
> Christopher Dorosky
> Senior Electronic Systems Engineer - Real Time Simulation
> Lockheed Martin Missiles and Fire Control - Dallas
> christopher.g.dorosky++at++lmco.com
> 972-603-2349
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