Drawing a cube with GlDrawElements ()?

Question

Is there a way to draw such a cube and, as a result, load only 8 vertices and 24 pointers to a graphics card? If so, how can this be done?

thank

Now I am doing it like this:

boxdims.x = w;
    boxdims.y = h;
    boxdims.z = d;
    center = c;

    GLfloat vboverticies[72];
    GLfloat vbonormals[18];
    Vertex3f verticies[24];

    //Top face
    verticies[0] = Vertex3f(-boxdims.x / 2.0f,boxdims.y / 2.0f, -boxdims.z / 2.0f);
    verticies[1] = Vertex3f(-boxdims.x / 2.0f,boxdims.y / 2.0f, boxdims.z / 2.0f);
    verticies[2] = Vertex3f(boxdims.x / 2.0f,boxdims.y / 2.0f, boxdims.z / 2.0f);
    verticies[3] = Vertex3f(boxdims.x / 2.0f,boxdims.y / 2.0f, -boxdims.z / 2.0f);


    //Bottom face
    verticies[4] = Vertex3f(-boxdims.x / 2.0f,-boxdims.y / 2.0f, -boxdims.z / 2.0f);
    verticies[5] = Vertex3f(boxdims.x / 2.0f,-boxdims.y / 2.0f, -boxdims.z / 2.0f);
    verticies[6] = Vertex3f(boxdims.x / 2.0f,-boxdims.y / 2.0f, boxdims.z / 2.0f);
    verticies[7] = Vertex3f(-boxdims.x / 2.0f,-boxdims.y / 2.0f, boxdims.z / 2.0f);


    //Left face
    verticies[8] = Vertex3f(-boxdims.x / 2.0f,-boxdims.y / 2.0f, -boxdims.z / 2.0f);
    verticies[9] = Vertex3f(-boxdims.x / 2.0f,-boxdims.y / 2.0f, boxdims.z / 2.0f);
    verticies[10] =Vertex3f(-boxdims.x / 2.0f,boxdims.y / 2.0f, boxdims.z / 2.0f);
    verticies[11] =Vertex3f(-boxdims.x / 2.0f,boxdims.y / 2.0f, -boxdims.z / 2.0f);


    //Right face
    verticies[12] =Vertex3f(boxdims.x / 2.0f,-boxdims.y / 2.0f, -boxdims.z / 2.0f);
    verticies[13] =Vertex3f(boxdims.x / 2.0f,boxdims.y / 2.0f, -boxdims.z / 2.0f);
    verticies[14] =Vertex3f(boxdims.x / 2.0f,boxdims.y / 2.0f, boxdims.z / 2.0f);
    verticies[15] =Vertex3f(boxdims.x / 2.0f,-boxdims.y / 2.0f, boxdims.z / 2.0f);

    //Front face
    verticies[16] =Vertex3f(-boxdims.x / 2.0f,-boxdims.y / 2.0f, boxdims.z / 2.0f);
    verticies[17] =Vertex3f(boxdims.x / 2.0f,-boxdims.y / 2.0f, boxdims.z / 2.0f);
    verticies[18] =Vertex3f(boxdims.x / 2.0f,boxdims.y / 2.0f, boxdims.z / 2.0f);
    verticies[19] =Vertex3f(-boxdims.x / 2.0f,boxdims.y / 2.0f, boxdims.z / 2.0f);

    //Back face
    verticies[20] =Vertex3f(-boxdims.x / 2.0f,-boxdims.y / 2.0f, -boxdims.z / 2.0f);
    verticies[21] =Vertex3f(-boxdims.x / 2.0f,boxdims.y / 2.0f, -boxdims.z / 2.0f);
    verticies[22] =Vertex3f(boxdims.x / 2.0f,boxdims.y / 2.0f, -boxdims.z / 2.0f);
    verticies[23] =Vertex3f(boxdims.x / 2.0f,-boxdims.y / 2.0f, -boxdims.z / 2.0f);




    for(int i = 0; i < 24; i++)
    {
        verticies[i].x += center.x;
        verticies[i].y += center.y;
        verticies[i].z += center.z;
    }


    int count = 0;
    for(int i = 0; i < 24; ++i)
    {
        vboverticies[count] = verticies[i].x;
        count++;
        vboverticies[count] = verticies[i].y;
        count++;
        vboverticies[count] = verticies[i].z;
        count++;
    }

    //glNormal3f(0.0, 1.0f, 0.0f);
    //glNormal3f(0.0, -1.0f, 0.0f);
    //glNormal3f(-1.0, 0.0f, 0.0f);
    //glNormal3f(1.0, 0.0f, 0.0f);
    //glNormal3f(0.0, 0.0f, 1.0f);
    //glNormal3f(0.0, 0.0f, -1.0f);
    vbonormals[0] = (0.0);
    vbonormals[1] = (1.0);
    vbonormals[2] = (0.0);

    vbonormals[3] = (0.0);
    vbonormals[4] = (-1.0);
    vbonormals[5] = (0.0);

    vbonormals[6] = (-1.0);
    vbonormals[7] = (0.0);
    vbonormals[8] = (0.0);

    vbonormals[9] = (1.0);
    vbonormals[10]= (0.0);
    vbonormals[11]= (0.0);

    vbonormals[12]= (0.0);
    vbonormals[13]= (0.0);
    vbonormals[14]= (1.0);

    vbonormals[15]= (0.0);
    vbonormals[16]= (0.0);
    vbonormals[17]= (-1.0);



    //Create the VBO
    glDeleteBuffers(1, &vboID);
    glGenBuffersARB(1, &vboID);
    glBindBufferARB(GL_ARRAY_BUFFER, vboID);
    glBufferDataARB(GL_ARRAY_BUFFER, (72 * sizeof(GLfloat)) + 
        (18 * sizeof(GLfloat)) , NULL, GL_STATIC_COPY);

    glBufferSubDataARB(GL_ARRAY_BUFFER_ARB, 0, 72 * sizeof(GLfloat), vboverticies);
    glBufferSubDataARB(GL_ARRAY_BUFFER_ARB, 72 * sizeof(GLfloat),
        18 * sizeof(GLfloat), vbonormals);


}

Answer 1

The answer is no.

If you need normals, you will need to have 24 vertices, since none of them have normals. Note that the example provided by shk does not handle normals.

Answer 2

Perhaps this will be useful - http://www.songho.ca/opengl/gl_vertexarray.html

Answer 3

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