[Mesa-dev] [RFC] [PATCH 0/3] Make Gallium aware of GL_TEXTURE_RECTANGLE

[Christoph Bumiller]

On 08/11/2010 08:34 PM, Luca Barbieri wrote:
>> I agree that if a texture was created as GL_TEXTURE_RECTANGLE, meaning that
>> all shaders use the TGSI_TEXTURE_RECT sampler type, it makes sense to use
>> unnormalized coordinates
...
> 
>> Some time ago I think Brian suggested to add PIPE_TEXTURE_RECT as another
>> texture type and make it match the meaning of GL_TEXTURE_RECTANGLE. We would
>> do this change but we had no time back then. This seems to be the solution
>> that would work best for everybody.
> 
> I think this would require extensive changes due to all the places
> that check for PIPE_TEXTURE_2D, and unduly burdens modern hardware
> (nv50+, r600+) which doesn't really care, since it supports everything
> orthogonally (BTW, note that OpenCL even requires to be able to
> mix&match samplers and sampler views in the shaders).

With nv50 and nvc0 (Fermi), coordinate normalization is still part of
the resource and not the sampler state. Even though the hardware does
support mix and match of samplers and images, this normalization bit
trashes the orthogonality/elegance.

> It seems best to minimize the impact of this legacy behavior as much
> as possible.
> 
> Is there any other factor that would balance all these disadvantages
> of introducing PIPE_TEXTURE_RECT?
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