“…In [64], the solution was optimized for the treatment of several receivers, by mapping in pre-process the lit polygons to a coarse grid to limit the number of intersection tests needed in RT. In [65], the use of the polar sweep algorithm [62] is added to compute an intra visibility matrix in pre-process. It stores the visibility relationship between each pair of geometrical elements (faces or edges), as the extreme angles for which some parts of the two elements are visible.…”