{
switch (key)
{
+ case 'n': glDisable ( GL_CULL_FACE ) ;
+ break ;
+ case 'f': glEnable ( GL_CULL_FACE ) ;
+ glCullFace ( GL_FRONT ) ;
+ break ;
+ case 'b': glEnable ( GL_CULL_FACE ) ;
+ glCullFace ( GL_BACK ) ;
+ break ;
case 27 :
case 'q':
exit(0);