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Visibility of a Point

To determine if some point P is visible, we shoot a ray from the cyclopean origin O (on tex2html_wrap_inline2962 and near the fish's mouth) to P (see Fig. gif). First, if tex2html_wrap_inline3120 and the angle between the ray and the fish's x-axis is less than 150 degrees then P is within the view volume. Second, to examine if P is occluded, we test if the ray intersects other objects (fishes or static obstacles) in the fish's view volume.

  figure1208


next up previous contents
Next: Occlusion Test Up: Computing Visibility Previous: Computing Visibility
Xiaoyuan TuJanuary 1996