Drawing a cube in open GL ES1 for the iphone

Hello friendly computer people,

I've been studying openGL with the book iPhone 3D programming from O'Reilly. Below I've posted an example from the text which shows how to draw a cone. I'm still trying to wrap my head around it which is a bit difficult since I'm not super familiar with C++.

Anyway, what I would like to do is draw a cube. Could anyone suggest the best way to replace the following code with one that would draw a simple cube?

const float coneRadius = 0.5f;
const float coneHeight = 1.866f;
const int coneSlices = 40;

{
    // Allocate space for the cone vertices.
    m_cone.resize(开发者_开发问答(coneSlices + 1) * 2);

    // Initialize the vertices of the triangle strip.
    vector<Vertex>::iterator vertex = m_cone.begin();
    const float dtheta = TwoPi / coneSlices;
    for (float theta = 0; vertex != m_cone.end(); theta += dtheta) {

        // Grayscale gradient
        float brightness = abs(sin(theta));
        vec4 color(brightness, brightness, brightness, 1);

        // Apex vertex
        vertex->Position = vec3(0, 1, 0);
        vertex->Color = color;
        vertex++;

        // Rim vertex
        vertex->Position.x = coneRadius * cos(theta);
        vertex->Position.y = 1 - coneHeight; 
        vertex->Position.z = coneRadius * sin(theta);
        vertex->Color = color;
        vertex++;
    }
}

Thanks for all the help.

If all you want is an OpenGL ES 1.1 cube, I created such a sample application (that has texture and lets you rotate it using your finger) that you can grab the code for here. I generated this sample for the OpenGL ES session of my course on iTunes U (I've since fixed the broken texture rendering you see in that class video).

The author is demonstrating how to build a generic 3-D engine in C++ in the book, so his code is a little more involved than mine. In this part of the code, he's looping through an angle from 0 to 2 * pi in a number of steps corresponding to coneSlices. You could replace his loop with a series of manual vertex additions corresponding to the vertices I have in my sample application in order to draw a cube instead of his cone. You'd also need to remove the code he has elsewhere for drawing the circular base of the cone.

In OpenGLES 1 you would probably draw a cub using glVertexPointer to submit geometry and glDrawArrays to draw the cube. See these tutorials:

http://iphonedevelopment.blogspot.com/2009/05/opengl-es-from-ground-up-table-of.html

OpenGLES is a C based library.