Angus Dorbie (dorbie++at++bitch.reading.sgi.com)
Tue, 21 Jan 1997 17:53:57 +0000
On Jan 21, 3:06pm, Graham Jones wrote:
> Subject: Infinite Reality, Colour matrix and pfTexEnv Component
> Hopefully the answer to these questions should be short and simple, I
> hope someone can help me:
>
> 1) More an OpenGL question than a specific Performer question:
> The glTexImage2D manual page states that RE, RE2 and VTX graphics
> systems do not support colour matrix transformations as textures are
> loaded or read back from texture memory. Does this apply to
> InfiniteReality graphics as well? I think so, but then I may just be
> doing something wrong.
Infinite Reality supports the glPixelTransfer transformations
on texture downloads.
>
> 2) Performer question - the pfTexEnv::setComponent call allows one
> component of an RGBA texture to be selected and used as a single
> component intensity texture. The manual says that a 16 bit RGBA texture
> could be used to provide 4 independent 4-bit intensity textures - I
> presume this is just an example, am I correct? I want to use a 32bit
> RGBA texture as separate 8 bit intensity textures as an alternative to
> the colour matrix transformation.
This relates to the IrisGL TV_COMPONENT_SELECT possible with
the texture environment and it's OpenGL equivalent.
This is possible with OpenGL on IMPACT and Infinite Reality
systems but one consideration is; has the OpenGL functionality
been implemented in Performer? It is probably has but if
not you may have to try:
glTexParameter(gltexhandle, GL_QUAD_TEXTURE_SELECT_SGIS, component);
This will enable you to select an 8 bit single component from a 32 bit
RGBA, but if you have to resort to OpenGL then the callbacks will be a
pain when using different components from a single texture in the same
scene.
Cheers,
Angus.
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