Another limitation of natural vision is occlusion. Occlusion is also
modeled in the visual perception of the artificial fish (see
Fig. 
). An object is ``seen'' if and only if some
part of it enters the visual range (or view volume) and it is not
fully occluded behind some other opaque object. Implementation details
will be described in the next section.
| Xiaoyuan Tu | January 1996 |
