int startGraphics(int width, int height)
{
    ...
    glEnable(GL_MULTISAMPLE);
    glEnable(GL_CULL_FACE);
    glEnable(GL_DEPTH_TEST);
    ...
}
void renderScene()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    ...
}