PM_ADD24 on RE

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2 total messages Started by Michael Manyin Wed, 06 Jan 1993 18:49

#80

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

43 lines
1934 bytes

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

-------
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

Re: PM_ADD24 on RE

#90

Author: Marc van Kempen
Date: Fri, 08 Jan 1993 00:40

38 lines
1553 bytes

manyin@helene.gsfc.nasa.gov (Michael Manyin) writes:


>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.


[ some stuff deleted ]


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

I don't know if anybody mentioned this work-around to you, I use it
succesfully on Indigo-Elan and Personal Iris.

First clear the window with color 256 (twice when using double
buffering) and than set writemask(0xff).
This will work on almost any machine, and is a lot faster for those that
emulate it in software.

marc.

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