Re: PM_ADD24 on RE

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#90

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

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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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Path: arc1-ca.pugleaf.net!sparky!uunet!mcsun!sun4nl!tuegate.tue.nl!rw7.urc.tue.nl!wmbfmk
From: wmbfmk@rw7.urc.tue.nl (Marc van Kempen)
Newsgroups: comp.sys.sgi.graphics
Subject: Re: PM_ADD24 on RE
Message-ID: <wmbfmk.726453631@rw7.urc.tue.nl>
Date: 8 Jan 93 00:40:31 GMT
References: <1993Jan6.134941@helene.gsfc.nasa.gov>
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