>This result could be less tight; for example, if you had a long corridor with many side rooms, and that long corridor was a single cell, then in Quake it would always try to render all the side rooms, whereas Thief would only try to render the entry cell to each of the side rooms (since those cells would always be adjacent to the corridor and visible), but Thief could cull the rooms themselves if they weren't currently visible.

Big if. You had screwed up if you left such a setup as one long vis chunk. Level designers would place vis boundaries strategically along a corridor to control this behavior. It was a bit of an art form but not exactly hidden knowledge, even the levels that shipped with quake SW had this kind of tuning built in.

Weird that at no point in this article is the engine overall referred to as what I and presumably most level/mod designers referred to it as - 'The Dark Engine'. Still, she's a classic. Tuned beautifully for the sneak/rpg gameplay of Thief and System Shock. Not at all suitable for the high speed multiplayer FPS gameplay of Quake. A comparison between the two is always interesting to see.