renderCamera.m

// cameraPos and angle are instance vars, obviously

- (void)renderCamera {
  GLfloat cameraHeightMax = 40.0;
  GLfloat cameraHeightMin = 8.0;
  
  if (cameraPos.z > cameraHeightMax) cameraPos.z = cameraHeightMax;
  if (cameraPos.z < cameraHeightMin) cameraPos.z = cameraHeightMin;
  
  // Setup camera
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  
  // Create perspective frustrum
  glFrustumf(-1.5, 1.5, -1.0, 1.0, 4.0, 200.0);
  
  // Translate it behind a bit
  glTranslatef(0.0, -1.5, 0.0);
  
  // Move camera above play plane
  glTranslatef(0.0, 0.0, -cameraPos.z);
  
  // Rotate the view to slightly down, staying pointed at origin
  glRotatef(-20.0, 1.0, 0.0, 0.0);
  
  // Spin camera to match angle of viewport
  glRotatef(-angle, 0.0, 0.0, 1.0);
  
  // Position camera
  glTranslatef(-cameraPos.x, -cameraPos.y, 0.0);
}