This poll is a follow-up for topic http://www.java-gaming.org/cgi-bin/JGNetForums/YaBB.cgi?board=xith3d;action=display;num=1070378327 “Pixel Shaders with Xith3d?”.
There are pros and cons in every approach, so lets vote.
It would be great if you add your comments with explanations why you prefer one approach or don’t like another.
Yuri
GLSL, any day of the week
Hi
No personal need for either right this second. I just think that going with a standard, rather than one manufactureres implementation is a good idea 
Endolf
I prefer to stay with standards.
tomcat
Standards, death to exclusive manufacturers’ shaders
Standards, standards, standards!
How well these ‘standards’ are supported on middle range hardware (pre GeforceFX) ? I know that a lot can be made with Cg there, while AFAIK opengl vertex/fragment program extension is just not supported at all. Please correct me if I’m wrong, but if it is true, I see a major counterargument to ‘standard’ shouting.
If we support the OpenGL shading language, is OpenGL 1.5 or OpenGL 2.0 required? I read the other thread, but don’t know how to interpret it correctly. (OpenGL 1.5 does not support the shading language, but it’s available as a set of extensions.)
[quote]I know that a lot can be made with Cg there, while AFAIK opengl vertex/fragment program extension is just not supported at all.
[/quote]
This is true, and I know only one vendor who supports GLSL (also sometimes named as GLslang) on their high-end cards - 3DLabs, and AFAIK GLSL is their development: http://www.3dlabs.com/support/developer/ogl2/index.htm. Currently this is approved as official ARB extension.
NVidia Cg can not be treated as vendor-specific language, at least because of it can generate code for ARB_vertex_program extension, supporrted by different vendors (say, 3DLabs and ATI). You can check FAQ at http://www.cgshaders.org/articles/interview_davidkirk02.php for more details. Cg is just one more layer on top of existing and supported OpenGL specs and extensions.
On the other hand, I read somewhere that NVidia has plans to support GLSL/GLslang.
Very important point is that for a moment I am not sure if there are bindings for GLSL extensions in JOGL (or other OpenGL bindings for Java), while functional Cg bindings are existing and tested. They include nice mechanisms for specifying parameters for high-level Cg programs, so it is much easier to integrate than other shading languages.
Yuri
Depends entirely on platform support. While there will be GLslang support for OSX, there is not even a peep from nVidia for almost 18 months about ANY support for Cg on OSX.
I’ve asked more than a few times and they don’t seem sincerely interested.
[quote]If we support the OpenGL shading language, is OpenGL 1.5 or OpenGL 2.0 required?
[/quote]
I don’t think you should loose compatibility with OpenGL 1.2, so if application does not use programmable shaders it should run no pbs on the older HW. Actually, app should (can) detect if these functions supported on the system before using them.
Yuri
[quote]I don’t think you should loose compatibility with OpenGL 1.2, so if application does not use programmable shaders it should run no pbs on the older HW.
[/quote]
That’s obvious. I wanted to know which OpenGL version is required to use the OpenGL shading language if we support it.
[quote]I wanted to know which OpenGL version is required to use the shading language if we support it.
[/quote]
Actually, this does not depend on OpenGL version but rather on availability of specific extensions:
You can start using Cg with OpenGL 1.3 if you have available extensions like NV_vertex_program, NV_vertex_program1_1 or ARB_vertex_program.
App should not rely on OpenGL version but only on presence of extension and/or function entry points, because of some vendors may decide to drop some older extensions, besides of they are part of OpenGL spec.
Yuri
Regarding the OpenGL version required for GLslang, looks like it requires OpenGL 1.4 or higher:
[quote]OpenGL Shading Language
This 865 KB pdf document describes a programming language that is a companion to OpenGL 1.4 and higher, called The OpenGL Shading Language.
[/quote]
This is from http://www.opengl.org/documentation/oglsl.html.
But again, OpenGL Shading Language is an OpenGL extension (actually, 3 separate extensions), so OpenGL version is not so important and major point if these extensions supported or not.
Yuri
The new Ati Catalyst v3.10 driver adds support for the OpenGL Shading Language.
http://www2.ati.com/drivers/Catalyst_310_Release_Notes.html
Good news I think because now Ati support this directly.
[Edit] Nvidia said in October, they contributed to the OpenGL Shading Language (what does this mean actually?).
[quote]Good news I think because now both, Nividia and Ati, support this.
[/quote]
Is there some info on that NVidia already supports GLslang?
Yuri
Unfortunately I just read in a press release from October about their contribution to the OpenGL shading language: http://www.nvidia.com/object/IO_9075.html
“[…] NVIDIA was also one of the primary contributors to the new OpenGL® Shading Language extension. […]”
Maybe I confused their contribution with “already supported by current drivers”… ? 
This is exacly what I meant - AFAIK, NVidia does not support GLslang yet. They have plans to add this, but for a moment they do not support it, so even if we’ll add GLslang to Xith3D right now this will be useless for majority of devs, especially on non-Windows platforms, while Cg will work at least on Windows & Linux.
Yuri
Cg is also mostly useless for users of non nVidia hardware. While I can go through the hassle of building a shader and compiling it with nvidias tools into something that can run on ATI hardware, if I do that - not really a whole lot of sense supporting Cg at all - as I’m just making an OpenGL call to render with the compiled shader.
OK, but Cg does also much more - parameter management, support for different low-level languages (at least, NV_vertex_program and ARB_vertex_program are supported).
OK, I had no chance to play with Cg on ATI cards, but I will get several ATI cards for tests soon and will definitely try this.
Yuri