In our animated marine world, we model clustered seaweeds (multiple
leaves originated from the same root) that are often observed in
nature. To perform efficient visibility check of seaweeds, we use a
rectangular bounding box for each seaweed cluster (see
Fig. 
). The visibility of a seaweed cluster is
determined by the visibility of the 8 corners of the corresponding
bounding box. If any of the corner points is visible, the seaweed
cluster is visible.
| Xiaoyuan Tu | January 1996 |