ATI_fragment_shader and parsing

OpenGL Development
#1

Hi all,
Before you tell me to go and get a new card, just hear me out for a second, humour me if you have to…

My Raedon 9200 supports ARBvp but not ARBfp, the fragment shader functionality is exposed as ATI_fragment_shader, however, it uses hardcoded OpenGL code instead of asm like txt files to parse (like ARBfp/vp and GLSL). There is an ATI_text_fragment_shader extention to do that, but that is only available under MacOSX which renders 90% of users (if not more) useless…

Does anybody know of a tool/library or another extention that can use text files to generate those fragment shaders for older ATI cards starting from 8500 to 9500? A tool is available for nvidia cards (called nvparse) to generate NV_register_combiners code from asm txt files, is there something like that for ATI cards? I have googled, but found nothing; Just a bunch of forums with people saying they are going to be building their own parser/compiler and that it is a good idea to support those cards, but nothing concrete…

Thanks in advance,
DP

#2

Go get a new card! :stuck_out_tongue: ;D

I’ve searched too and couldn’t find anything. I finally got used to the extension and wrote everything by hand. Cool extension, can be very powerful with enough tweaking. Too bad R200 is missing depth texture support…

#3

Dang, crack and woffle! Looks like im going to have to stick it out with ARBfp/vp and GLSL and buy a new card. Or create another shader path for R200…

Anybody know how Doom3 did it? I think it supports the R200 for pixel lighting and bumpmapping…

#4

[quote=“darkprophet,post:3,topic:24108”]
I didn’t find any “shader” files for NV_RC or ATI_FS, so I guess both were hardcoded in C code. If you go for it, my suggestion is this: write a simple parser to read the shader from a file and automatically generate the OpenGL calls (I’ve done this in Marathon). Very easy to implement but saves a lot of time.

#5

Yes thats the plan, but my fear is that im going to have to code 4 files. 1 GLSL, 1 fragment, 1 vertex, and 1 for both ATI_fragment_shader and NV_register_combine. Either that, or write a complicated parser to parse the fragment/vertex asm files and generate the OpenGL code like you said.

I still haven’t looked at the NV_register_combine extention, is it similar to ATI’s in terms of functionality? Any thing one of them doesn’t support that the other does?

#6

[quote=“darkprophet,post:5,topic:24108”]
Yeah, writing such a general renderer is a big problem. I did it like that in Marathon initially, but then decided it wasn’t worth the trouble and now I only have GLSL plus an NV_RC path for the crappy FX line of cards. Your decision should be based on what you want to support of course (we’re going to support FX+, R300+).

By the way, I didn’t mean an ARB_fragment_program to ATI_FS converter (very difficult), just a simple text representation of ATI_FS that can be easily modified without recompiling.

[quote=“darkprophet,post:5,topic:24108”]
ATI_fragment_shader is the equivalent of NV_register_combiners + NV_texture_shader and both are the equivalent of DX <= 1.4 pixel shaders. Some differences:

  • ATI_FS has a better internal color precision [-8, 8], whereas NV_RC has [-1, 1] with 9-bit signed fixed point values.
  • NV_register_combiners is supported even on Geforce 1 & 2 (no NV_texture_shader though, only on NV20+), whereas ATI_FS needs R200+.
  • NV has kept the NV_RC & NV_TS hardware on newer cards (super fast), whereas ATI is emulating the ATI_FS functionality with the fragment shader hardware on R300+ (I’ve not verified this, but even if it’s true it’s more than fast enough anyway).

Other than these, they are mostly equal in terms of functionality.

#7

Yes, i heard that as well about them and not verified them myself too…So i can’t really comment on how marginal the speed difference is, but if anything, it is definetly measurable…

Marathon is definetly looking good, i dont particularly know the details, is it going to be opensourced? or is it used for a commercial game? Either way, im happy what Java can achieve with games…

#8

Marathon is an engine for strategy games (mainly). It’s in a good state, but far from ready and not our only project, not even our first priority actually. We do plan to release a commercial game on top of it, but that’s obviously going to take a while. As for opensourcing it, time will tell. I certainly plan to release the renderer + tools someday though.

#9

:o

http://realmforge.tigris.org/source/browse/realmforge/trunk/src/Axiom/RenderSystems/OpenGL/ATI/PixelShader.cs?rev=5&view=auto&content-type=text/vnd.viewcvs-markup

Its in C#, and it also changes DX8.1 pixel shaders to ATI_fragment_shader stuff, so not ARBfp…But its a start :slight_smile:

Anybody feels up to the challenge of writing a lexer for ARBfp?

DP