Vertex Buffer Objects Problem

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1.Vertex Buffer Object problem

    Hello,

    I've just implement the ARB_vertex_buffer_objet in one my my program,
all works perfectly, but ... All run Twice SLOWER than a normal loop.

    I create all things like that :

    GLuint vbo_v,vbo_nv...;

    glGenBuffersARB(1,&vbo_v);
    glBindBufferARB(GL_ARRAY_BUFFER_ARB,vbo_v);

glBufferDataARB(GL_ARRAY_BUFFER_ARB,3*nbrv*sizeof(float),v,GL_STATIC_DRAW_AR
B);

    glGenBuffersARB(1,&vbo_nv);
    glBindBufferARB(GL_ARRAY_BUFFER_ARB,vbo_nv);

glBufferDataARB(GL_ARRAY_BUFFER_ARB,3*nbrv*sizeof(float),nv,GL_STATIC_DRAW_A
RB);
    ...

    Where v and nv and pointers on 2 arrays (vertices and vertices
normals) - i do the same with vertex color, tex coords ...

    glGenBuffersARB(1,&vbo_f);
    glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB,vbo_f);

glBufferDataARB(GL_ELEMENT_ARRAY_BUFFER_ARB,3*nbrf*sizeof(int),f,GL_STATIC_D
RAW_ARB);

    For indexs

    When i bind all that

                glEnableClientState(GL_COLOR_ARRAY);
                glBindBufferARB(GL_ARRAY_BUFFER_ARB,vbo_vc);
                glColorPointer(4,GL_UNSIGNED_BYTE,0,NULL);

                glEnableClientState(GL_NORMAL_ARRAY);
                glBindBufferARB(GL_ARRAY_BUFFER_ARB,vbo_nv);
                glNormalPointer(GL_FLOAT,0,NULL);

                glEnableClientState(GL_VERTEX_ARRAY);
                glBindBufferARB(GL_ARRAY_BUFFER_ARB,vbo_v);
                glVertexPointer(3,GL_FLOAT,0,NULL);

                // DRAWING
                glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB,vbo_f);
                glDrawElements(GL_TRIANGLES,3*nbrf,GL_UNSIGNED_INT,NULL);

                glDisableClientState(GL_VERTEX_ARRAY);
                glDisableClientState(GL_COLOR_ARRAY);
                glDisableClientState(GL_NORMAL_ARRAY);

    I have with a normal loop about 60 fps and 30 fps when using VBO
    I run on an AMD ATHLON 2Ghz 512Mo GeForce4MX

    All Works perfectly but TWICE slower than normal loop with glNormals,
glVertex, glTexCoord ...
    Why ? Did i do something wrong ? Isn't vertex buffer objects are
supposed to increase the number of fps and not make your programs run slower
? Help !

    Thanks in advanced for your help

2.Vertex Arrays, Vertex Buffer Objects

Hi list.

I implemented rendering using display lists, vertex arrays, and vertex
buffer objects. And guess what was the faster ? ... display lists !

It should mean that I implemented badly those array stuff.
For the VBO part, I'm quite sure that today drivers are not correctly
implemented - systematically crash on some ATI hardware, even if
extention is detected, poor perfs on nVidia. After all, it runs as
fast as plain vertex arrays.
For the VA part ... I guess all static geometry could be rendered
using glLockArray() ... ? I think this is called compiled vertex array
? Is this an improvement compared to plain vertex arrays ?
Will I have to go to VAR to achieve correct perfs ?

Thx for enlightments

SeskaPeel.

3.Changing vertex color after vertex buffer and index buffer definition

Hi,

Say you have this custom vertex structure:

struct CUSTOMVERTEX
{
	float x, y, z;
	DWORD color;
};

Is it possible once you've defined values for a vertex 
buffer using that structure to subsequently change the 
color for a vertex that you defined? If so, how?

Thanks :)

4.Multiple objects in a single vertex buffer.

The book I'm reading shows as illustration example, multiple objects
in a single v-buffer.  These more primitive though: sphere, box and a
cylinder.  Is it wise to have a v-buffer handle more than one object?

5.how scale a pVB vertex buffer object ?

I have a vertex buff obj, it's a meshed(tessulated) square in D3DX8,
 Vertex *v;

    g_pd3dDevice->CreateVertexBuffer( g_nTriCount*3*sizeof(Vertex),
                                      D3DUSAGE_WRITEONLY,
D3DFVF_CUSTOMVERTEX,
                                      D3DPOOL_MANAGED, &g_pWallVB );

    g_pWallVB->Lock( 0, 0, (BYTE**)&v, 0 );

    float dX = 1.0f/(g_nNumVertsX-1);
    float dZ = 2.0f/(g_nNumVertsZ-1);//dz=1.0f/
    int i = 0;

    for( int z = 0; z < (g_nNumVertsZ-1); ++z )
    {
        for( int x = 0; x < (g_nNumVertsX-1); ++x )
        {
            v[i].p = D3DXVECTOR3(10*x*dX, 0.0f, 10*z*dZ );
            v[i].n = D3DXVECTOR3(0.0f, 1.0f, 0.0f);
            ++i;
            v[i].p = D3DXVECTOR3(10*x*dX, 0.0f, 10*(z+1)*dZ );
            v[i].n = D3DXVECTOR3(0.0f, 1.0f, 0.0f);
            ++i;
            v[i].p = D3DXVECTOR3(10*(x+1)*dX, 0.0f, 10*(z+1)*dZ );
            v[i].n = D3DXVECTOR3(0.0f, 1.0f, 0.0f);
            ++i;
            v[i].p = D3DXVECTOR3(10*x*dX, 0.0f, 10*z*dZ );
            v[i].n = D3DXVECTOR3(0.0f, 1.0f, 0.0f);
            ++i;
            v[i].p = D3DXVECTOR3(10*(x+1)*dX, 0.0f, 10*(z+1)*dZ );
            v[i].n = D3DXVECTOR3(0.0f, 1.0f, 0.0f);
            ++i;
            v[i].p = D3DXVECTOR3(10*(x+1)*dX, 0.0f, 10*z*dZ );
            v[i].n = D3DXVECTOR3(0.0f, 1.0f, 0.0f);
            ++i;
        }
    }

    g_pWallVB->Unlock();


How can I rescale its size.

6. Vertex buffer objects: how to improve speed further ?

7. GL_OUT_OF_MEMORY ( vertex buffer objects )

8. Missing Function Definitions for Vertex Buffer Objects (VBOs) on Linux