dependant texture problems ARB_fragment_program

OpenGL OpenGL: Advanced Coding
1

Hi, im pretty new to GL, and im having trouble using dependant texture reads in a ARB_fragment_shader. i would imagine that my code should produce something, but currently it dosent produce any artifacts on the screen.

I have simplified my program to try and texture one polygon that is passed into the card with tex coords to carry out a lookup on a 3d texture, the result of this 3d texture read i want to use in another lookup for colouring.

The data i’m intrested in is encoded in the 3d textures red channel, from this i want the red channels value to be used in a 1D texture lookup to get a RGBA quadruple for the final fragment colour.

Im unsure if my shader code is incorrect, or the way i manipulate the ogl state?

Im using a GeForceFX card
SHADER CODE

!!ARBfp1.0
TEMP R0;
TEX R0, fragment.texcoord[0], texture[0], 3D;
TEX result.color, R0.x, texture[1], 1D;
END

DRAW CODE

glClear(GL_COLOR_BUFFER_BIT);
glEnable(GL_VERTEX_PROGRAM_ARB);
glEnable(GL_FRAGMENT_PROGRAM_ARB);
pglBindProgramARB(GL_VERTEX_PROGRAM_ARB, vrVertexShader);
pglBindProgramARB(GL_FRAGMENT_PROGRAM_ARB, vrFragmentShader);
glEnable(GL_TEXTURE_3D);
glBindTexture(GL_TEXTURE_3D, texName[0]);
glEnable(GL_TEXTURE_1D);
glBindTexture(GL_TEXTURE_1D, texName[1]);
glCallList(vrSliceGeometryList);
glDisable(GL_VERTEX_PROGRAM_ARB);
glDisable(GL_FRAGMENT_PROGRAM_ARB);
glFlush ();

could it be the way i specify the texture, or have i done something wrong in the draw proc, or maybe the shader, or maybe my state is setup wrong ??

any help would be greatly appreciated!!

2

You have to select the active texture stage before binding a (multi)texture:

glActiveTextureARB(GL_TEXTURE0_ARB);glBindTexture(GL_TEXTURE_3D, texName[0]);
glActiveTextureARB(GL_TEXTURE1_ARB);glBindTexture(GL_TEXTURE_1D, texName[1]);

You do not need the “glEnable(GL_TEXTURE_nD)” calls when using ARB or NV fragment programs.

The rest of your code looks fine …

Klaus

3

Thanks Klaus, that worked a treat, I thought it would be something simple like that, but being new to GL, i didint know where i could get the documentation for such things !!

Thanks again

4

No problem. IMHO the newest OpenGL Redbook covering OpenGL 1.4 is all you need: http://www.opengl.org/documentation/red_book_1.0/

And, of course, the OpenGL Extension Registry (although sometimes hard to read): http://oss.sgi.com/projects/ogl-sample/registry/

Have fun with OpenGL,
Klaus