Thread: Implemented vertex arrays, prob. rendering

I got interested in Shamino's perpetual plight to implement a central data format. Subsequently, I implemented a mechanism for my 'own' basic layout that can be rendered using vertex arrays.

Now, as far as I can see I've gotten things to work, but when I render everything using glVertex/TexCoord pointer and then glDrawArrays, I can an exception in my ATI driver (accessing something it shouldn't be). When I render the data 'manually' using 'stop and start' immediate mode GL, it renders fine, meaning that the data is 'correct.' Somewhere, I'm goofing up bigtime.

Below is the two different ways I render 'NT_MODELs'

PHP Code:

#if    1
            int    start_index = mesh_ref.mStartVertIndex;
//also tried start_index = mdl_ref.mpIndexArray[mesh_ref.mStartVertIndex]
            NT_GL(glVertexPointer(3,GL_FLOAT,sizeof(NT_VERTEX),&mdl_ref.mpVertices[start_index].vertex))
            NT_GL(glTexCoordPointer(2,GL_FLOAT,sizeof(NT_VERTEX),&mdl_ref.mpVertices[start_index].tex_coord))
            NT_GL(glDrawElements(GL_TRIANGLES,mesh_ref.mNumMeshVerts,GL_UNSIGNED_INT,&mdl_ref.mpIndexArray[mesh_ref.mStartVertIndex]))
#else
            gpNTGLAPI->ntglBegin(GL_TRIANGLES);
            for(int  j = 0; j < mesh_ref.mNumMeshVerts; j += 3)
            {    
                for(int k = 0; k < 3; k++)    //plot each coordinate w/texture coord
                {
                    int    index = mdl_ref.mpIndexArray[j + k + mesh_ref.mStartVertIndex];
                    
                    NT_VERTEX    &    vert_ref = mdl_ref.mpVertices[index];
                    gpNTGLAPI->ntglTexCoord2f(vert_ref.tex_coord[0],vert_ref.tex_coord[1]);
                    gpNTGLAPI->ntglVertex3fv(vert_ref.vertex);
                }
                
            }
            gpNTGLAPI->ntglEnd();
#endif 


First way crashes, second renders perfectly.

This is similar, if not ultimately identical in structure, to how I render quake3 faces (a quake3 face is ultimately a mesh, the bsp has an index array)

PHP Code:

    i = mvQuake3SingleTexturedFaces.at(k);
    
        gpTextureManager->BindTexture(GL_TEXTURE_2D,gpBSP->mpGLTextures[gpBSP->mpFaces[i].textureID]);
        
        NT_GL(glVertexPointer(3,GL_FLOAT,sizeof(tBSPVertex),&gpBSP->mpVertices[gpBSP->mpFaces[i].startVertIndex].vPosition))
        NT_GL(glTexCoordPointer(2, GL_FLOAT,sizeof(tBSPVertex), &gpBSP->mpVertices[gpBSP->mpFaces[i].startVertIndex].vTextureCoord))

        //doesn't work when you pass GL_FLOAT instead of int
        NT_GL(glDrawElements(GL_TRIANGLES, gpBSP->mpFaces[i].numMeshVerts, GL_UNSIGNED_INT, &gpBSP->mpIndexArray[gpBSP->mpFaces[i].meshVertIndex])) 


This is quite strange indeed. I'm sure I'm doing something simple wrong.

I can't see anything wrong with the code you've shown.

All I can suggest is making sure you called glEnable(GL_VERTEX_ARRAY) before rendering (if not, this could perhaps create an access violation as you described?), and perhaps seeing if OpenGL returns any errors in addition to the driver exception.

I've never bothered with vertex arrays, so I can't be of much help here.

I got it working, I was computing my mpIndexArray data incorrectly.

The index array is supposed to represent the offset *from the start vertex*, not actual indexes.

Them be fightin' words!!!!

I must admit that I wasted a good amount of time solving a problem that was

a) stupid

b) stupid

c) already implemented in DirectX

Oh well

Hey mr!

Well, hey!

*angry face*

I meant it was stupid as in the solution was obvious, and further agravated by the fact that, as bubba mentioned, this is already implemented in the dx API. I was not trying to say that this was an easy problem to solve, in general.