help about VBO's

bonanza

Unregistered

Post: #1

Sep 6, 2007 — 05:46 AM

i like to use VBO's for rendering. i int this with:

Code:

glGenBuffers(1, &vboId1);

    glBindBuffer(GL_ARRAY_BUFFER, vboId1);

    glBufferData(GL_ARRAY_BUFFER, [complete count] * sizeof(GLfloat), data, GL_STATIC_DRAW);    

    glGenBuffers(1, &vboId2);

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboId2);

    glBufferData(GL_ELEMENT_ARRAY_BUFFER, numIndexes*3 * sizeof(GLushort), vertexIndicies, GL_STATIC_DRAW);

and render with this:

Code:

glEnableClientState( GL_VERTEX_ARRAY );

    glEnableClientState( GL_TEXTURE_COORD_ARRAY );

    glEnableClientState(GL_NORMAL_ARRAY);

    glBindBuffer(GL_ARRAY_BUFFER, vboId1);

    glVertexPointer(   3, GL_FLOAT, 8*sizeof(GLfloat), data );

    glTexCoordPointer( 2, GL_FLOAT, 8*sizeof(GLfloat), &data[3] );

    glNormalPointer(      GL_FLOAT, 8*sizeof(GLfloat), &data[5] );

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboId2);

    glDrawElements( GL_TRIANGLES, numIndexes*3, GL_UNSIGNED_SHORT, 0 );

    glDisableClientState(GL_VERTEX_ARRAY);

    glDisableClientState(GL_NORMAL_ARRAY);

    glDisableClientState( GL_TEXTURE_COORD_ARRAY );

but i get no output.

when i render without VBO's (with vertex arrays) it works.

any suggestions ??

NYGhost

Member

Posts: 157
Joined: 2002.12

Post: #2

Sep 6, 2007 — 06:57 AM

the last parameter of this call:

Code:

glDrawElements( GL_TRIANGLES, numIndexes*3, GL_UNSIGNED_SHORT, 0 );

should be the address of the triangle vertex indexes.

bonanza

Unregistered

Post: #3

Sep 6, 2007 — 07:13 AM

mh,
dont work too

NYGhost

Member

Posts: 157
Joined: 2002.12

Post: #4

Sep 6, 2007 — 07:52 AM

not sure that more than one buffer can be active at the same time.
try attaching the vertex buffer only (vboId1) to see what happens.

I use a single buffer for vertex, vertex indexes, normal, and tex coords.

OneSadCookie

Luminary

Posts: 5,125
Joined: 2002.04

Post: #5

Sep 6, 2007 — 03:50 PM

With VBOs, the last parameter to gl*Pointer is the offset into the buffer that the data begins, not a pointer to the data.

bonanza

Unregistered

Post: #6

Sep 6, 2007 — 10:57 PM

i have read several times its better to use one array for all informations, and use a stride value. than use a indexarray to render.
i cant find any error, without vbo's, that works well.
arghhhhh....

btw. you can activate more than one buffer

edit

Code:

    glVertexPointer(   3, GL_FLOAT, 8*sizeof(GLfloat), 0);

    glTexCoordPointer( 2, GL_FLOAT, 8*sizeof(GLfloat), 0 );

    glNormalPointer(      GL_FLOAT, 8*sizeof(GLfloat), 0 );

the last parameter should be 0. ????

ok works better but, the texturecoordinates looks strange

edit2

Code:

#define BUFFER_OFFSET(i) ((char *)NULL+(i))

glVertexPointer(   3, GL_FLOAT, 8*sizeof(GLfloat), 0);

glTexCoordPointer( 2, GL_FLOAT, 8*sizeof(GLfloat), BUFFER_OFFSET(3*sizeof(GLfloat) ));

glNormalPointer(      GL_FLOAT, 8*sizeof(GLfloat), BUFFER_OFFSET(5*sizeof(GLfloat)) );

works well.

thanks...

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