Re: PVS generation

Olivier Montanuy (
Wed, 12 Jun 1996 12:11:02 +0200

Date: Wed, 12 Jun 1996 12:11:02 +0200
From: Olivier Montanuy <>
Subject: Re: PVS generation

>The basic idea is determining "portals": polygons
>that allow for looking into adjacent leafs.

Well, if they really have to determine portals, I can't help
but wonder why the heck they need a BSP tree.

Anyone who played Duke Nukem knows that a portal-based scheme
is more flexible than a BSP based scheme.

> The generated frustrums/beams will be split and cut by each
>subsequent portal, until they are completely stopped by a wall.

That would probably be a suitable description for the 3D engines
of both Descent and Duke Nukem.

> Every other leaf reached by the light is part of the PVS.
> Any other ideas?

Calculate PVS on the fly, like every serious game does ;-)

Actually, if your leaf has areas not accessible to players, those
areas might register into the PVS other leaves that no player will
ever see. Then the engine will calculate all the 3D transform for
these leaves, just to discard it later. So I suspect the PVS
calculation need not be very precise.

Anyway there ain't no good alternative to an Indigo Impact.