I'm developing a portal-based scene manager. Basically all it does is to check the portals against the camera frustum, and render their associated portal zones accordingly. Is there any way my editor can generate portal zones automatically with the user having to set the portals themselves only? For example, the Max Payne 1/2 engine ("Max-FX") only required to set the portal quads, unlike the C4 engine where you also have to explicitly set the portal zones.