In 3D games, why would the viewing field be a frustum? Why not a pyramid?
You would still have to do culling to figure out what's in the field, and to me it seems a pyramid field is no harder to do culling math than a frustum field.
Is it just because of worries that a small object may wander directly in front of the camera, blocking the entire view? To me that seems more a problem of game design and good auto-camera control, rather than a choice of viewing field geometry. (Also, that worry can still exist with a frustum field, if the near plane is relatively close to camera.)
Btw, I'm under the impression that the vast majority of games use a frustum, correct me if I'm wrong.