gl_ModelViewMatrixInverse

OpenGL
1

Hi everyone,

I’m currently developing some water rendering where I need to transform eye space coordinates to world space coodinates.

My dev. platform is a GeForce FX, and I happily use the ‘gl_ModelViewMatrixInverse’ variable to do the maths.

I just tested on a ATI Radeon 9700 (Cat. 4.8) system, and the GLSL compiler spits at me that it doen’t know ‘gl_ModelViewMatrixInverse’ !!

Does anyone know exactly which parts of GLSL ATI supports ?

Thanks,

Nicolas.

2

Maybe the 4.8 drivers didn’t implement the version of the GLSL spec which added the inverse matrices. Try updating your drivers.

3

Yep, since my 1st post, I also tried the Cat. 4.9 without luck either…

Hmmm, I think I’ll be off to make another NV/ATI branch in my code…

4

gl_ModelViewMatrixInverse is defined in GLSL version 1.1. AFAIK there is no GLSL 1.1 implementation right now, not from ATI nor from nVidia. Maybe 3DLabs supports it.

5

If you don’t want to make different branches in your code for implementations that don’t support this yet, just invert the matrix yourself and pass as a uniform.

6

Originally posted by Corrail:
gl_ModelViewMatrixInverse is defined in GLSL version 1.1. AFAIK there is no GLSL 1.1 implementation right now, not from ATI nor from nVidia. Maybe 3DLabs supports it.
ahh that explains why a few of the inverse/tranpose thingees weren’t recognized, though gl_ModelViewMatrixInverse does work (66.00 nvidia drivers) i use it to get the camera position

vec4 camera_pos = gl_ModelViewMatrixInverse[3];

gotta admit ive been having a few troubles though by passing in mat4 as uniforms with the 66.00 drivers
eg
Vertex info

Internal error: assembly compile error for vertex shader at offset 0:
– error message –
line 1, column 1: error: invalid vertex program header

unifrom mat4 objectspace;

main()
{	vec4 obj_vert = vec4( gl_Vertex.xyz, 1.0 ) + vec4( gl_MultiTexCoord3.xyz, 0.0 ) * gl_Color.a;	

	vec4 mv_vert = gl_ModelViewMatrix * objectspace * obj_vert;

gl_Position		= gl_ModelViewProjectionMatrix * objectspace * obj_vert;
}

remove either of the objectspace’s though + it works!

7

Try to write uniform correctly. :wink:
For better performance: instead of two matrix * matrix multiplications do this:

vec4 vTemp = objectspace * obj_vert;
vec4 mv_vert = gl_ModelViewMatrix * vTemp;
gl_Position = gl_ModelViewProjectionMatrix * vTemp;
8

Originally posted by Corrail:
gl_ModelViewMatrixInverse is defined in GLSL version 1.1. AFAIK there is no GLSL 1.1 implementation right now, not from ATI nor from nVidia. Maybe 3DLabs supports it.
I can confirm that, 3DLabs cards (at least Realizm) has version 110 of GLSL (that means that has xxInverse and xxxInverseTranspose matrices (and all other 110 stuff))

9

Ahf thanks for the infos, I should read specs more carefully !

10

This topic was automatically closed 183 days after the last reply. New replies are no longer allowed.