Visibility of rectangular objects in L<inf>1</inf> metric

Given a set of n rectangles (2-dimensional) parallel to xy-plane, and a point P(x,y,z) in 3-dimensional space, we find the visibility of all rectangles i.e., the set of all visible points of rectangles from P in L1 metric, in script O sign(n4) time and script O sign(n3) space. We also discuss the cases where the point P moves along a straight line and the rectangles are inserted and deleted dynamically.