Framebuffer Object Extension Examples

Quick example :

  //RGBA8 2D texture,24 bit depth texture, 256x256
  glGenTextures(1, &color_tex);
  glBindTexture(GL_TEXTURE_2D, color_tex);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
  //NULL means reserve texture memory, but texels are undefined
  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, 256, 256, 0, GL_BGRA, GL_UNSIGNED_BYTE, NULL);
  //-------------------------
  glGenFramebuffersEXT(1, &fb);
  glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fb);
  //Attach 2D texture to this FBO
  glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, color_tex, 0);
  //-------------------------
  glGenRenderbuffersEXT(1, &depth_rb);
  glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT24, 256, 256);
  //-------------------------
  //Attach depth buffer to FBO
  glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, depth_rb);
  //-------------------------
  //Does the GPU support current FBO configuration?
  GLenum status;
  status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
  switch(status)
  {
     case GL_FRAMEBUFFER_COMPLETE_EXT:
     cout<<"good";
  default:
     HANDLE_THE_ERROR;
  }
  //-------------------------
  glClearColor(0.0, 0.0, 0.0, 0.0);
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  //-------------------------
  glViewport(0, 0, 256, 256);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(0.0, 256.0, 0.0, 256.0, -1.0, 1.0); 
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  //-------------------------
  glDisable(GL_TEXTURE_2D);
  glDisable(GL_BLEND);
  glEnable(GL_DEPTH_TEST);
  //-------------------------
  glColor3f(1.0, 1.0, 0.0);
  glBegin(GL_TRIANGLES);
  glVertex2f(0.0, 0.0);
  glVertex2f(256.0, 0.0);
  glVertex2f(256.0 , 256.0);
  glEnd();
  //-------------------------
  GLubyte pixels[4*4*4];
  glReadPixels(0, 0, 4, 4, GL_BGRA, GL_UNSIGNED_BYTE, pixels);
  //pixels 0, 1, 2 should be white
  //pixel 4 should be black