Vertex Buffer Object - usage HELP!

[Mr.Pink]

i want to draw an .obj model in openGL using VBO, but i am confused with "index buffer", "index array" and other legacy functionality.
i cannot found anything clear about that on the web

i wrote an .obj reader, so in my system memory i have this situation

3 STL c++ vector representing data ridden from file

vector<Vec3>        m_vertexCoords; 
vector<Vec2>        m_textureCoords; 
vector<Vec3>        m_normalCoords;

unsigned int        m_numVertices;
unsigned int        m_numTextures;
unsigned int        m_numNormals;

(Vec* is a class with * float members)


and

 struct Face
{
    vector<unsigned int> vertices;
    vector<unsigned int> texcoords;
    vector<unsigned int> normals;
};

vector<Face>        m_faces;

unsigned int        m_numFaces;

this vector of faces(triangles) each one containing indices to previous vectors of float

can someone tell me how to initialize buffer and draw them each frame? thanks

 

[cass]

Hi Mr Pink,

It's not clear to me that you need VBOs just yet.

You first need to restructure your data such that you have a single index list instead of a separate index for each vertex attribute. Then you should be able to render using conventional (slow) vertex arrays. There are lots of examples of how to do this.

Once you get your code working with conventional arrays, you'll want to create VBOs to hold the arrays. Again, there are numerous examples (including the VBO extension spec) for how to do this.

Thanks -
Cass

 

[Mr.Pink]

Hi Mr Pink,

It's not clear to me that you need VBOs just yet.

You first need to restructure your data such that you have a single index list instead of a separate index for each vertex attribute. Then you should be able to render using conventional (slow) vertex arrays. There are lots of examples of how to do this.

Once you get your code working with conventional arrays, you'll want to create VBOs to hold the arrays. Again, there are numerous examples (including the VBO extension spec) for how to do this.

Thanks -
Cass

can you tell me some sources for tutorials/documentation/code using VBO drawing mesh from a file? thanks again

 

[cass]

There's a good whitepaper on efficient VBO usage here:
http://www.spec.org/gpc/opc.static/vbo_whitepaper.html

As for rendering from file, I would suggest looking online for
examples that do the kind of rendering you want.

 

[Mr.Pink]

For other people with the same problem,
I have found very useful the step by step tutorial for loading .obj mesh with VBO at this link:
http://www.robthebloke.org/opengl_programming.html