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List:       dri-devel
Subject:    Re: r200 and ATI_fragment_shader
From:       Roland Scheidegger <rscheidegger_lists () hispeed ! ch>
Date:       2005-01-09 17:38:00
Message-ID: 41E16BF8.8080802 () hispeed ! ch
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Philipp Klaus Krause wrote:
> Dave Airlie schrieb:
> 
>> Just to update, I've looked at the fragment shader stuff and the
>> documentation I have isn't enough to implement the spec, we only have
>> access to the second stage registers (PP_CNTL - states second or only 
>> pass
>> registers....)
> 
> 
> Is it enough to implement GL_ARB_texture_crossbar?
Definitively. No additional information at all should be needed to 
implement it. The reason it's not implemented is the that the r200 does 
not have any "spare" register in the fragment pipeline. It has only 6, 
which can be used both as inputs and outputs. But you need to make sure 
you don't overwrite a register value which you got from texture sampling 
if you might need it again later on, which would easily happen with a 
trivial implementation of crossbar. It would be easy to add with the 
default enabled 4 or 2 tmus, but not quite so trivial for all 6. I think 
Ian was working on this some time ago.

Roland


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