Re: [Dri-devel] NV_texture_rectangle?

[Brian P. <br...@tu...>]

Ian Romanick wrote:
> On Mon, Sep 30, 2002 at 09:22:00AM -0600, Brian Paul wrote:
> 
>>Ian Romanick wrote:
>>
>>>Hello all.
>>>
>>>I noticed that NV_texture_rectangle appeared in the R100 driver string after
>>>then recent R200 merge.  I did some looking around, and found that it is
>>>explicitly enabled in the R200 driver and has code to support rectangular
>>>textures.  It seems that it is enabled by default in Mesa.  Is this correct?
>>
>>It's enabled for the R200 driver and software rendering only.
> 
> 
> That may be the desired result, but extras/Mesa/src/extensions.c, line 113
> tells me differently:
> 
>     { ON,  "GL_NV_texture_rectangle",  F(NV_texture_rectangle) },
> 
> It shows up in the extension string from glxinfo on the R100 driver.

Oops, that's an accident.  I'll fix it.


>>>I didn't dig deep enough in Mesa to see if it would somehow automatically
>>>convert a rectangle to a power-of-two, so this might be okay.
>>
>>It does not do that.  The texture targets GL_TEXTURE_2D and
>>GL_TEXTURE_RECTANGLE_NV are distinct.
> 
> 
> Okay.  That's what I figured.  Thanks for saving my dig time. :)
> 
> [snip]
> 
> 
>>Simulating NPOT textures with conventional targets could be pretty tricky.
>>Note that NPOT texture coordinates range from [0,Width]x[0,Height], not
>>[0,1]x[0,1] as normal textures do.  Some clamp/repeat modes aren't supported
>>either.
> 
> 
> Right.  Mipmap (and ansio?) filter modes are also forbidden.  I gave this a
> bit more thought after my last message.  I don't think this is something
> that Mesa could automatically do.  It would have to be done on a per-driver
> basis.  You'd have to change the texture upload routines (easy) and the emit
> routines (hard).  If NV_texture_rectangle still used [0,1]x[0,1], it would
> be pretty easy.

I suppose we could multiply the S and T coords by the texture size, but that
might upset the LOD calculation which is needed to choose between the mini-
fication and magnification filter (even though we don't have mipmaps).

-Brian