OpenGL Vertex Buffer Array/Object

[Denarius]

Hey,

I wanted to use the vertex buffer array or object from OpenGl, but I can't get it to work.

This is what I do:

I create a widget and setup the opengl stuff.

void Gui::GLWidget::initializeGL(){
    glShadeModel(GL_SMOOTH);							// Enable Smooth Shading
    glClearColor(0.0f, 0.0f, 0.0f, 0.5f);				// Black Background
    glClearDepth(1.0f);									// Depth Buffer Setup
    glEnable(GL_DEPTH_TEST);							// Enables Depth Testing
    glDepthFunc(GL_LEQUAL);								// The Type Of Depth Testing To Do
    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);	// Really Nice Perspective Calculations
 
    GLfloat LightAmbient[]= { 0.5f, 0.5f, 0.5f, 1.0f };
    GLfloat LightDiffuse[]= { 1.0f, 1.0f, 1.0f, 1.0f };
    GLfloat LightPosition[]= { 0.0f, 0.0f, 2.0f, 1.0f };
 
    glLightfv(GL_LIGHT1, GL_AMBIENT, LightAmbient);				// Setup The Ambient Light
    glLightfv(GL_LIGHT1, GL_DIFFUSE, LightDiffuse);
    glLightfv(GL_LIGHT1, GL_POSITION,LightPosition);
 
    glEnable(GL_LIGHT1);
    glEnable(GL_CULL_FACE);
    glCullFace(GL_BACK);
}

void Gui::GLWidget::initializeGL(){
    glShadeModel(GL_SMOOTH);							// Enable Smooth Shading
    glClearColor(0.0f, 0.0f, 0.0f, 0.5f);				// Black Background
    glClearDepth(1.0f);									// Depth Buffer Setup
    glEnable(GL_DEPTH_TEST);							// Enables Depth Testing
    glDepthFunc(GL_LEQUAL);								// The Type Of Depth Testing To Do
    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);	// Really Nice Perspective Calculations

    GLfloat LightAmbient[]= { 0.5f, 0.5f, 0.5f, 1.0f };
    GLfloat LightDiffuse[]= { 1.0f, 1.0f, 1.0f, 1.0f };
    GLfloat LightPosition[]= { 0.0f, 0.0f, 2.0f, 1.0f };

    glLightfv(GL_LIGHT1, GL_AMBIENT, LightAmbient);				// Setup The Ambient Light
    glLightfv(GL_LIGHT1, GL_DIFFUSE, LightDiffuse);
    glLightfv(GL_LIGHT1, GL_POSITION,LightPosition);

    glEnable(GL_LIGHT1);
    glEnable(GL_CULL_FACE);
    glCullFace(GL_BACK);
}

To copy to clipboard, switch view to plain text mode 

Then I paint the stuff in here:

void Gui::GLWidget::paintGL(){
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);	// Clear Screen And Depth Buffer
    glLoadIdentity();									// Reset The Current Modelview Matrix
    glTranslatef(0.0, 0.0, -30.0);						// Move Left 1.5 Units And Into The Screen 6.0
 
    world->render();
}
 
void Bfe::World::render(){
    qreal timeElapsed = ((qreal)time.elapsed() / 1000.0);
    time.restart();
 
    camera->render();
 
    heightMap->render(wireFrame);
 
    for(QVector<Render::RenderObject *>::Iterator i = objects.begin(); i < objects.end(); i++)
    {
        (*i)->render();
    }
}
 
//I start rendering the objects with my for loop, which is one cube at the moment. But it doesn't draw
 
Render::Cube::Cube(){
    //Create the object matrix
    // cube ///////////////////////////////////////////////////////////////////////
    //    v6----- v5
    //   /|      /|
    //  v1------v0|
    //  | |     | |
    //  | |v7---|-|v4
    //  |/      |/
    //  v2------v3
    //
    //
    // TODO: Vertex Array doesn't work yet!
 
    // vertex coords array
    GLfloat vertices[] =  {1,1,1,  -1,1,1,  -1,-1,1,  1,-1,1,        // v0-v1-v2-v3
                1,1,1,  1,-1,1,  1,-1,-1,  1,1,-1,        // v0-v3-v4-v5
                1,1,1,  1,1,-1,  -1,1,-1,  -1,1,1,        // v0-v5-v6-v1
                -1,1,1,  -1,1,-1,  -1,-1,-1,  -1,-1,1,    // v1-v6-v7-v2
                -1,-1,-1,  1,-1,-1,  1,-1,1,  -1,-1,1,    // v7-v4-v3-v2
                 1,-1,-1,  -1,-1,-1,  -1,1,-1,  1,1,-1};   // v4-v7-v6-v5
    this->vertices = &vertices[0];
    // normal array
    GLfloat normals[] = {0,0,1,  0,0,1,  0,0,1,  0,0,1,             // v0-v1-v2-v3
                         1,0,0,  1,0,0,  1,0,0, 1,0,0,              // v0-v3-v4-v5
                         0,1,0,  0,1,0,  0,1,0, 0,1,0,              // v0-v5-v6-v1
                         -1,0,0,  -1,0,0, -1,0,0,  -1,0,0,          // v1-v6-v7-v2
                         0,-1,0,  0,-1,0,  0,-1,0,  0,-1,0,         // v7-v4-v3-v2
                         0,0,-1,  0,0,-1,  0,0,-1,  0,0,-1};        // v4-v7-v6-v5
    this->normals = &normals[0];
 
    // color array
    GLfloat colors[] = {1,1,1,  1,1,0,  1,0,0,  1,0,1,              // v0-v1-v2-v3
                        1,1,1,  1,0,1,  0,0,1,  0,1,1,              // v0-v3-v4-v5
                        1,1,1,  0,1,1,  0,1,0,  1,1,0,              // v0-v5-v6-v1
                        1,1,0,  0,1,0,  0,0,0,  1,0,0,              // v1-v6-v7-v2
                        0,0,0,  0,0,1,  1,0,1,  1,0,0,              // v7-v4-v3-v2
                        0,0,1,  0,0,0,  0,1,0,  0,1,1};             // v4-v7-v6-v5
    this->colors = &colors[0];
 
}
 
void Render::Cube::render(){
    glEnableClientState(GL_NORMAL_ARRAY);
    glEnableClientState(GL_COLOR_ARRAY);
    glEnableClientState(GL_VERTEX_ARRAY);
 
    glNormalPointer(GL_FLOAT, 0, normals);
    glColorPointer(3, GL_FLOAT, 0, colors);
    glVertexPointer(3, GL_FLOAT, 0, vertices);
 
        glPushMatrix();
            // rotate + half the size, else the cube is somewhat under the ground
            glTranslatef(position.x(), position.y() + 1, position.z());
 
            glDrawArrays(GL_FLOAT, 0, 24);
 
        glPopMatrix();
 
    glDisableClientState(GL_NORMAL_ARRAY);
    glDisableClientState(GL_COLOR_ARRAY);
    glDisableClientState(GL_VERTEX_ARRAY);
 
}

void Gui::GLWidget::paintGL(){
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);	// Clear Screen And Depth Buffer
    glLoadIdentity();									// Reset The Current Modelview Matrix
    glTranslatef(0.0, 0.0, -30.0);						// Move Left 1.5 Units And Into The Screen 6.0

    world->render();
}

void Bfe::World::render(){
    qreal timeElapsed = ((qreal)time.elapsed() / 1000.0);
    time.restart();

    camera->render();

    heightMap->render(wireFrame);

    for(QVector<Render::RenderObject *>::Iterator i = objects.begin(); i < objects.end(); i++)
    {
        (*i)->render();
    }
}

//I start rendering the objects with my for loop, which is one cube at the moment. But it doesn't draw

Render::Cube::Cube(){
    //Create the object matrix
    // cube ///////////////////////////////////////////////////////////////////////
    //    v6----- v5
    //   /|      /|
    //  v1------v0|
    //  | |     | |
    //  | |v7---|-|v4
    //  |/      |/
    //  v2------v3
    //
    //
    // TODO: Vertex Array doesn't work yet!

    // vertex coords array
    GLfloat vertices[] =  {1,1,1,  -1,1,1,  -1,-1,1,  1,-1,1,        // v0-v1-v2-v3
                1,1,1,  1,-1,1,  1,-1,-1,  1,1,-1,        // v0-v3-v4-v5
                1,1,1,  1,1,-1,  -1,1,-1,  -1,1,1,        // v0-v5-v6-v1
                -1,1,1,  -1,1,-1,  -1,-1,-1,  -1,-1,1,    // v1-v6-v7-v2
                -1,-1,-1,  1,-1,-1,  1,-1,1,  -1,-1,1,    // v7-v4-v3-v2
                 1,-1,-1,  -1,-1,-1,  -1,1,-1,  1,1,-1};   // v4-v7-v6-v5
    this->vertices = &vertices[0];
    // normal array
    GLfloat normals[] = {0,0,1,  0,0,1,  0,0,1,  0,0,1,             // v0-v1-v2-v3
                         1,0,0,  1,0,0,  1,0,0, 1,0,0,              // v0-v3-v4-v5
                         0,1,0,  0,1,0,  0,1,0, 0,1,0,              // v0-v5-v6-v1
                         -1,0,0,  -1,0,0, -1,0,0,  -1,0,0,          // v1-v6-v7-v2
                         0,-1,0,  0,-1,0,  0,-1,0,  0,-1,0,         // v7-v4-v3-v2
                         0,0,-1,  0,0,-1,  0,0,-1,  0,0,-1};        // v4-v7-v6-v5
    this->normals = &normals[0];

    // color array
    GLfloat colors[] = {1,1,1,  1,1,0,  1,0,0,  1,0,1,              // v0-v1-v2-v3
                        1,1,1,  1,0,1,  0,0,1,  0,1,1,              // v0-v3-v4-v5
                        1,1,1,  0,1,1,  0,1,0,  1,1,0,              // v0-v5-v6-v1
                        1,1,0,  0,1,0,  0,0,0,  1,0,0,              // v1-v6-v7-v2
                        0,0,0,  0,0,1,  1,0,1,  1,0,0,              // v7-v4-v3-v2
                        0,0,1,  0,0,0,  0,1,0,  0,1,1};             // v4-v7-v6-v5
    this->colors = &colors[0];

}

void Render::Cube::render(){
    glEnableClientState(GL_NORMAL_ARRAY);
    glEnableClientState(GL_COLOR_ARRAY);
    glEnableClientState(GL_VERTEX_ARRAY);

    glNormalPointer(GL_FLOAT, 0, normals);
    glColorPointer(3, GL_FLOAT, 0, colors);
    glVertexPointer(3, GL_FLOAT, 0, vertices);

        glPushMatrix();
            // rotate + half the size, else the cube is somewhat under the ground
            glTranslatef(position.x(), position.y() + 1, position.z());

            glDrawArrays(GL_FLOAT, 0, 24);

        glPopMatrix();

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

}

To copy to clipboard, switch view to plain text mode 

Can anyone give me a heads-up on what I'm doing wrong?

Also, can anyone tell me if and how I can use a vertex buffer object?

[minimoog]

Did you setup projective matrix and viewport?

VBO is just buffer for vertices. Vertices are stored in server area (GPU).

glGenBuffers(1, &vboID);
glBindBuffer(GL_ARRAY_BUFFER, vboID);
glBufferData(GL_ARRAY_BUFFER, 24 * 3 * sizeof(float), vertices, GL_STATIC_DRAW);

glGenBuffers(1, &vboID);
glBindBuffer(GL_ARRAY_BUFFER, vboID);
glBufferData(GL_ARRAY_BUFFER, 24 * 3 * sizeof(float), vertices, GL_STATIC_DRAW);

To copy to clipboard, switch view to plain text mode 

When you have bind VBO object then glVertexPointer (and others glColorPointer...) take their data from VBO. The last parameter (pointer to vertices) indicates offset in the binded VBO object. Now, you can store vertices, normals, colors in separate VBO objects, or all together in one VBO object. It's up to you.