GL_ARB_shadow_ambient

[vvolkman]

Anybody know why NVIDIA doesn't seem to implement GL_ARB_shadow_ambient on any of the cards I've seen. Not even the Quadro4 700 seems to have it.

I believe that one of the ATI Radeon 9x00 has GL_ARB_shadow_ambient

[Bert]

Originally posted by vvolkman
Anybody know why NVIDIA doesn't seem to implement GL_ARB_shadow_ambient on any of the cards I've seen. Not even the Quadro4 700 seems to have it.

I believe that one of the ATI Radeon 9x00 has GL_ARB_shadow_ambient

Yes, R300 has it: delphi3d (http://www.delphi3d.net/hardware/extsupport.php?extension=GL_ARB_shadow_ambient)

I guess NVIDIA is just following the ARB's own recommandation.
(3) What are the downsides of this extension?
This extension places some arithmetic in the texture sampling logic which would otherwise be better implemented in the texture combine logic.
Also, there probably aren't many (if any) other uses for this logic other than shadow ambient term.
Those who already implement advanced texture combine modes probably won't want to implement this extension.


So it is not needed because you can easily achieve the same effect with ARB_texture_env_combine.

However, I guess it would only be ASMOP for NVIDIA's driver guys to support it. If enough people bug them about it then it might get in :)

[phred]

Really, you can duplicate ARB_shadow_ambient with ARB_texture_env_combine??? I must have stared at that equation for hours, trying to find a way to make it work. Pleeeeease tell me your secret.

In my defense, I'd like to point out that the doc in the extension registry mentions only NV_register_combiners as an example extension to use. As it is, opening that proverbial Pandora's can of worms (or whatever) just wasn't worth it to me.