As we have indicated earlier, the artificial fish's vision sensor has access to the geometry, material property, and illumination information about the world that is available to the graphics pipeline for rendering purposes. In addition, the vision sensor can interrogate the world model database to identify nearby objects and interrogate the physical simulation to obtain information such as the instantaneous positions and velocities of objects of interest. In this way, the vision sensor extracts from the 3D virtual world only some of the most useful information that piscine visual processes can provide real fishes about their world, such as the colors, sizes, distances, and identities of visible objects.
A basic item of information in terms of the artificial fish's
behavioral repertoire is the overall brightness of the environment,
which is obtained as the mean intensity of the retinal image
rendered from the vantage point of the fish's cyclopean vision sensor.
Fig. 
and shows examples of
retinal images acquired by a fish ``witnessing'' another fish falling
prey to a fishing line.
Figure: Fisheye view of the world showing fishing line.
Figure: Fisheye view of the world showing hooked fish.
| Xiaoyuan Tu | January 1996 |