View Full Version : Help with ARB_vertex_program

04-11-2003, 04:06 PM
I have been trying to fined examples of the ARB_vertex_program EXT but have had very little success. I have read through the spec.txt and found the example of implement a simple ambient, specular, and diffuse infinite lighting

ATTRIB iPos = vertex.position;
ATTRIB iNormal = vertex.normal;
PARAM mvinv[4] = { state.matrix.modelview.invtrans };
PARAM mvp[4] = { state.matrix.mvp };
PARAM lightDir = state.light[0].position;
PARAM halfDir = state.light[0].half;
PARAM specExp = state.material.shininess;
PARAM ambientCol = state.lightprod[0].ambient;
PARAM diffuseCol = state.lightprod[0].diffuse;
PARAM specularCol = state.lightprod[0].specular;
TEMP xfNormal, temp, dots;
OUTPUT oPos = result.position;
OUTPUT oColor = result.color;

# Transform the vertex to clip coordinates.
DP4 oPos.x, mvp[0], iPos;
DP4 oPos.y, mvp[1], iPos;
DP4 oPos.z, mvp[2], iPos;
DP4 oPos.w, mvp[3], iPos;

# Transform the normal to eye coordinates.
DP3 xfNormal.x, mvinv[0], iNormal;
DP3 xfNormal.y, mvinv[1], iNormal;
DP3 xfNormal.z, mvinv[2], iNormal;

# Compute diffuse and specular dot products and use LIT to compute
# lighting coefficients.
DP3 dots.x, xfNormal, lightDir;
DP3 dots.y, xfNormal, halfDir;
MOV dots.w, specExp.x;
LIT dots, dots;

# Accumulate color contributions.
MAD temp, dots.y, diffuseCol, ambientCol;
MAD oColor.xyz, dots.z, specularCol, temp;
MOV oColor.w, diffuseCol.w;

I have tried it out but it displays nothing?
I have managed to get the basic example from Nutty site to work so I think all init code is working but I am not sure how to deal with the various attributes/materials?

This is how I draw the triangle:

glBindProgramARB(GL_VERTEX_PROGRAM_ARB, my_program);

glTranslatef(0.0f, 0.0f, -140.0f);

glVertex3f(0.0f, 100.0f, 0.0f);

glVertex3f(-100.0f, 0.0f, 0.0f);

glVertex3f(100.0f, 0.0f, 0.0f);

I think I need to pass in some extra attributes but donít know witch or how?

Any help/link would be appreciated.


04-15-2003, 01:54 AM
If the vertex program displays nothing, it means that the program is "refused".
Have you checked what errors are returned ?

04-16-2003, 01:26 AM
You program renders the triangle when not using the vertex program?
What about the projection matrix, the viewport, the light initialisation, etc.?
For debugging clear the background to some screaming color to see if you're rendering black-on-black.

04-17-2003, 08:43 AM
Thank for replying,

I have got it to work now. It was the comment in the program, after I put \n\ on the end of them the program worked. I have loaded lots of different ASE models and all but one look correct. The one that looks incorrect is green instead of purple?


04-17-2003, 10:59 AM
Originally posted by FredFlint:
I have loaded lots of different ASE models and all but one look correct. The one that looks incorrect is green instead of purple?
I guess this has to do with your ASE loading class/function. I don't think the vertex program is causing this.