Shader Programs finally - Java-Gaming.org

Goliat

Junior Member

Shader Programs finally

« Posted 2006-07-05 20:41:12 »

today i tried to create a simple vertex shader ... and although i finally got around compiling some glsl code with nvidias cg compiler i'm not quite happy with the results

first: nvidias compiler creates wrong 'machine code' (or however those compiled shaders are called)
i found a very simple example on wikipedia.com:

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void main(void)
{
    gl_Position = ftransform();
}

which should be the simplest vertex program around ... using the cg compiler ( with -oglsl -profile arbvp1 parameters ) i get this:

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!!ARBvp1.0
# cgc version 1.4.0000, build date Sep 26 2005 22:13:28
# command line args: -v -oglsl -profile arbvp1
# source file: wave.cg
#vendor NVIDIA Corporation
#version 1.0.02
#profile arbvp1
#program main
#semantic gl_ModelViewProjectionMatrixTranspose
#var float4 gl_Vertex : $vin.POSITION : POSITION : -1 : 1
#var float4 gl_Position : $vout.POSITION : HPOS : -1 : 1
#var float4x4 gl_ModelViewProjectionMatrixTranspose :  : c[1], 4 : -1 : 1
PARAM c[5] = { program.local[0..4] };
DP4 result.position.w, vertex.position, c[4];
DP4 result.position.z, vertex.position, c[3];
DP4 result.position.y, vertex.position, c[2];
DP4 result.position.x, vertex.position, c[1];
END
# 4 instructions, 0 R-regs

which doesn't contain any error ... but isn't the correct result
the correct version (and the one that is displaying stuff onscreen) would be:

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!!ARBvp1.0
PARAM c[4] = { state.matrix.mvp };
DP4 result.position.w, vertex.position, c[3];
DP4 result.position.z, vertex.position, c[2];
DP4 result.position.y, vertex.position, c[1];
DP4 result.position.x, vertex.position, c[0];
END

any idea if i just have to change some parameters of cgc ?

second: why do i even have to compile the glsl stuff myself?
i searched the web and found some pages that tell the user to let opengl compile the glsl source directly using the method void glCompileShaderARB(GLhandleARB program);

last: i have used this shader stuff for the first time today ... so if i have made a capital fault in my approach ... please point me at it Undecided

Golly

Niwak

Junior Member

Re: Shader Programs once again

« Reply #1 - Posted 2006-07-06 10:25:34 »

First question ; NVidia compiler creates a valid program. You just have to bind your transposed model view projection matrix to the program local parameter n° 1 and everything will work fine. It is stated in the comment ;

1	#var float4x4 gl_ModelViewProjectionMatrixTranspose : : c[1], 4 : -1 : 1

Second question ; You need to compile the GLSL code yourself because Xith3D doesn't support high level shader but only assembly ones.

Last question ; my own point of view is that using assembly shaders is an entirely deprecated way of using shaders. So if you really want to use shaders either add support for high level shaders to Xith3D or don't use Xith3D.

Vincent

Amos Wenger

Senior Member

Everything's possible, but not everything's fun...

Re: Shader Programs once again

« Reply #2 - Posted 2006-07-06 12:32:47 »

Quote from: Niwak on 2006-07-06 10:25:34

Last question ; my own point of view is that using assembly shaders is an entirely deprecated way of using shaders. So if you really want to use shaders either add support for high level shaders to Xith3D or don't use Xith3D.

How hard is it ?

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Goliat

Junior Member

Re: Shader Programs once again

« Reply #3 - Posted 2006-07-06 20:07:25 »

may i point you at this fine piece of html code: http://www.lighthouse3d.com/opengl/glsl/index.php?ogloverview

the opengl part doesn't look hart ... although i have no deeper knowledge of opengl :/

Goliat

Junior Member

Re: Shader Programs once again

« Reply #4 - Posted 2006-07-07 13:58:30 »

i guess i have implemented glsl support for xith3d ... i'm astonished about myself ... 0o

i'd commit it to the toolkit but it relies on some changes in the core ... and i'm not sure if it works completly ... so i'll play around with it some time today, implement the lwjgl parts (i've done jsr231 first) and post a patch this evening or tomorrow ...

maybe i'll catch arne today ... than i'll send him my stuff

greetz goliat

EDIT: i just noticed there is no way to specify parameters ... but i guess it won't take long to implement that ... now i'll be of to my parents ... cya guys

EDIT2: just one last question ... does xith uses opengl 2.0 functions? or the ARB stuff?
i used the ARB way ... should i?

Marvin Fröhlich

Senior Member

May the 4th, be with you...

Re: Shader Programs once again

« Reply #5 - Posted 2006-07-07 14:14:17 »

Quote from: Goliat on 2006-07-07 13:58:30

..., implement the lwjgl parts (i've done jsr231 first) and post a patch this evening or tomorrow ...

Is it a difference? Did you notice the least changes in Canvas3DWrapper, RenderLoop and Xith3DEnvironment. There should be no need to do anything different for LWJGL.

Goliat

Junior Member