PM_ADD24 on RE

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#80

From: Michael Manyin
Date: Wed, 06 Jan 1993 18:49

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On Dec 28th, I posted the following:

> We are porting a program from a VGX platform to a Crimson/RealityEngine,
> and have been finding it difficult to make full use of the 4096-entry
> colormap when lrectwrite'ing  8-bit images.
> 
> Specifically, we suspect that the call
> 
> pixmode( PM_ADD24, 256 );
> 
> on the RealityEngine, is the problem.
> 
> 
> In fact, any integer offset greater than 0 produces anomalous behavior.
> 
> The pixmode manual page claims that "Pixel addition can...
> be used to offset the range of a color map image",
> and our code  works fine on VGX and Indigo Elan machines.

Several people replied; the bug is recognized and real.
A couple SGI people got involved (thanks, guys!) and so
I can summarize the status of the bug:

There is an "internal bug report" already on file; while the
behavior was supposed to be fixed in an upcoming maintenace release,
it is not in 4.0.5G .   It should be fixed in 5.0.

Of course, if you have memory to burn, you can store data in 16 bit
pixels, and do the offset yourself.


Mike Manyin

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cross posted to:
comp.sys.sgi
comp.sys.sgi.graphics

--------------------------------------------------------------------
Michael Manyin                         NASA/GSFC
manyin@helene.gsfc.nasa.gov            Lab for Atmospheres, Code 912
US: (301) 286-7825                     Greenbelt, Maryland  20771

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From: manyin@helene.gsfc.nasa.gov (Michael Manyin)
Subject: PM_ADD24 on RE
Message-ID: <1993Jan6.134941@helene.gsfc.nasa.gov>
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Date: Wed, 6 Jan 1993 18:49:41 GMT
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