Re: [Gnu3dkit-dev] OGL 2.0 shading

[Philippe C . D . Robert]

Hi,

I know the interview and I also know Cg (a little, at least), but - or 
therefore - I think that OpenGL 2.0 SLang will be the way to go when 
doing OpenGL, not Cg.

For the 3DKit I believe the RenderMan Shader Language will be the best 
solution, it is more powerful and flexible. But of course it will be 
possible to implement a 3DKit OpenGL renderer backend using Cg or SLang.

This said, anyone who wants to contribute a Cg based renderer for the 
3DKit will be welcome, of course, but it will probably not be me...:-)

BTW the OpenGL 2.0 work makes steady progress (there is a weekly held 
SIG ARB meeting), the specs are scheduled for Siggraph 2003.

-Phil

On Tuesday, February 4, 2003, at 09:39  Uhr, Gerard Iglesias wrote:

> Philippe C.D. Robert wrote:
>
> > Hi,
> >
> > did someone play with the shader compiler of the OGL 2.0 proposal 
> > form 3DLabs? If yes, could this be used as foundation or starting 
> > point for our shader compiler?
>
> I am reading what I can around the shading language, especially I read 
> this QA :
>                                        
> http://www.cgshaders.org/articles/interview_davidkirk02.php
>
> And found this one :
>
> * What's the difference between an "offline" shader language (such as 
> RenderMan) and a "real-time" shader language such as Cg? Why can't the 
> former just be compiled directly to assembly code for GPUs?*
>
> Not only is Cg a "real-time" shader language, Cg has been designed to 
> be hardware friendly and hardware efficient. This means that Cg should 
> run well on most modern GPUs. Cg is like C - C for graphics, or C for 
> GPUs. Cg specifies data types, data connections, and arithmetic and 
> graphics operation primitives that exist in GPUs.
>
> RenderMan is a still higher language and is custom designed for 
> shading, not for optimal execution on GPUs. There are several 
> universities and tool providers who are in the process of developing a 
> compiler that translates from RenderMan shaders to Cg code. That 
> provides the best of both worlds. You get the high level shader focus 
> of RenderMan combined with the runtime compilation and efficient 
> execution of Cg on GPUs.
>
> Cg is also more than a shading language. Cg can be used to program any 
> function that can be run on GPUs, including geometry, physics, 
> collision detection, and also many non-graphics tasks.
>
>
>
> The other things are interesting to read also....
>
> And I find their work more visible and active than the one from 
> 3DLabs, didn't see anything new from a long time, while NVIdia promise 
> version for OSX soon.
>
> What do you think about this?
>
>   Sincerely
>
>        Gerard
>
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--
Philippe C.D. Robert
http://www.nice.ch/~phip