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vertex array problem

Started by cignox1 Apr 7, 2006 at 8:03 AM 2 replies 650+ views

Original Post

Apr 7, 2006 at 8:03 AM

In order to learn how to use VBOs, I'm currently trying to make vertex array work. And they don't :-( Not all the polygons are rendered (more or less half of them aren't), but I know that both vertices and faces are correct (if I try to render using immediate mode, everything works). Is there some common mistake that beginners usually make and that can lead to this errot? Don't know if you need code, but anyway:


    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glTranslatef(pos[0], pos[1], pos[2]);
    glRotatef(rot_angle, rot_axis[0], rot_axis[1], rot_axis[2]);

    glColor3f(1.0,1.0,1.0);
    //Declares the vertex arrays
    glEnableClientState(GL_VERTEX_ARRAY);
    glVertexPointer(3, GL_FLOAT, 0, vertices);
    if(normals)
    {
        glEnableClientState(GL_NORMAL_ARRAY);
        glNormalPointer(GL_FLOAT, 0, normals);
    }
    else glDisableClientState(GL_NORMAL_ARRAY);

    //Draw the geometry
    glDrawElements(GL_TRIANGLES, nfaces, GL_UNSIGNED_SHORT, faces);

Thank you!

echohead

Apr 7, 2006 at 9:10 AM

change the last line to:

glDrawElements(GL_TRIANGLES, 3 * nfaces, GL_UNSIGNED_SHORT, faces);

The second parameter refers to the number of elements in the connectivity array, not the number of faces.

cignox1

Apr 7, 2006 at 9:29 AM

I-DON'T-BELIVE-IT!!
This is the second dummy error today... Thank you a lot!
Anyway, in my defense, I would like to quote the reference pages that I use:

Quote:

count
Specifies the number of elements to be rendered.

Since the first parameter was GL_TRIANGLES, I interpreted this as number of faces 8-)

Thank you again and rate++!

CrazyCdn

Apr 7, 2006 at 12:49 PM

As you likely know, thats 1.1 specifications. You can get the latest ones, for free, from opengl.org. I think its even a pdf file.

Also, I had the same issue, so don't feel bad.

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