BitwiseOR

OpenGL Extensions allow us to use graphics hardware without delving into many specifics. The first one we will look at is fairly easy to use and understand, and it is a requirement for other extensions that do much more interesting manipulations. GL_ARB_depth_texture allows us to create a texture from the depth component of the scene. This will allow us to do shadow maps later on.

Set Up

In this example I will be using OglExt, but there are many different extension managers out there and all are easy to use. I like OglExt because it doesn’t require an initialization step like the OpenGL Extension Wrangler requires. I will also be using GLWindow as it is an easy to use OpenGL framework. This example works just as well in GLUT or any other window manager you can find. Here is the main file that we will be working with. Each step is outlined.

#include "GLWindow.h"
#include <gl/gl.h>
#include <gl/glu.h>
#include <gl/glaux.h>
#include <gl/OglExt.h>

#define SIZE 512

class DepthTexture : public GLWindow
{
public:
    GLuint texture;

    bool init()
    {
        // Check that extension is supported

        // Create texture
        // Make texture active
        // Fiddle with texture parameters

        // Initialize texture memory using DEPTH_TEXTURE for internal format and format

        return true;
    }

    void draw()
    {
        // clear the depth and color buffers
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glLoadIdentity();

        // Set viewpoint

        // Draw scene that we will take the depth of

        // Copy the current depth buffer to the texture

        // clear the depth and color buffers
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glLoadIdentity();

        // Set viewpoint
        // Draw a quad with the texture attached
    }
};

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    DepthTexture* window = new DepthTexture();

    // Set Window size
    window->starting_width = SIZE;
    window->starting_height = SIZE;
    window->mainLoop(hInstance, hPrevInstance, lpCmdLine, nCmdShow);
}

Pages: 1 2