triangles and quads which are not BFC-enabled (e.g. in non-certified files, or in a section of a file enclosed in
0 BFC NOCLIP
...
0 BFC CLIP
must be treated non-oriented, i.e., it cannot be derived an "inside" and "outside" facing surface of them.
They must be rendered from whatever side you look at them.
In OpenGL as far as I remember, there's a global rendering option by which you can turn on and off the logic
if to render such a surface or not. I don't think that you can turn and off it for individual quads or triangles, though.
Thus, the only solution that comes to my mind is: if you encounter such data, you will probably be forced to turn off
the CW/CCW optimization logic of your OpenGL renderer for the _whole_ scene...
0 BFC NOCLIP
...
0 BFC CLIP
must be treated non-oriented, i.e., it cannot be derived an "inside" and "outside" facing surface of them.
They must be rendered from whatever side you look at them.
In OpenGL as far as I remember, there's a global rendering option by which you can turn on and off the logic
if to render such a surface or not. I don't think that you can turn and off it for individual quads or triangles, though.
Thus, the only solution that comes to my mind is: if you encounter such data, you will probably be forced to turn off
the CW/CCW optimization logic of your OpenGL renderer for the _whole_ scene...