RE: IR./PF support for index or palette texture
Mark Mueller (mmueller++at++es.com)
Tue, 25 Feb 1997 09:40:31 -0700
>----------
>From: Angus Dorbie[SMTP:dorbie++at++bitch.reading.sgi.com]
>Sent: Tuesday, February 25, 1997 1:17 AM
>To: Mark Mueller; 'info-performer++at++sgi.com'
>Subject: Re: IR./PF support for index or palette texture
>
>On Feb 24, 12:35pm, Mark Mueller wrote:
>> Subject: IR./PF support for index or palette texture
>> I have a sim application where I want to use palette texture on an
>> Infinite Reality. I have heard that IR. supports a 256 bit paletted
>
>You mean 8 bit giving 256 entries.
Yes, that is what I meant, sorry.
>
>> texture and have also seen the palette texture extension for OGL. Does
>
>I think this is only implemented in Cosmo OpenGL, (the recently available
>software only pentium PC OpenGL 1.1 implementation for Windows ), at this
>time.
After posting and a lot of searching I found some keywords that were
helpful, ie. tlut, and texture color table. This in turn lead me to the
book OpenGL on Silicon Graphics Systems. I found quite a bit of info and
leads there.
>
>> anyone have any suggestions for how I can activate this mode and animate
>> my texture based palette etc. on an IR.? Thank You.
>>
>
>You have several options.
>
>You could use an intensity map and use a colour look up table but you
>may encounter interpolation problems if you use mipmapping of bilinear
>filtering due to the lookup happening after the texture interpolation.
I would also loose the ability to do fog and other per fragment
operations on the result, right?
>
>You could story the animation in texture memory and use a different
>texture each frame, you have a lot of texture memory on iR.
>
>You could download one texture image from an animated sequence each frame
>each frame and store the animation in system RAM, you have a lot of
>bandwidth to texture memory on iR.
Both of these may put more of a load on the host and texture bandwidth
than I may have room for. The textures (multiple maps) will be much
larger than the number of materials in the lookup table (one table),
thus it is considerably easier to just animate the lookup table - which
I think the IR will support.
>
>Cheers,
>Angus.
Unless you think it is a bad idea, I am going to pursue some of the
things mentioned in the OGL SGI book in "The Texture Color Table
Extension". The funny thing I have discovered so far is that the
documentation insists that the maximum size of the texture color table
is 8 bit, but the IR will let me load a 10 bit table. I haven't tried
drawn anything yet.
Angus, thank you for your help
Santé,
Mark.
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