A method (20 or 500) and system (200) for method for computing wireless signal diffraction in a three-dimensional space can include the steps of selecting at least a source point, finding (19) sinkpoints that fail to have a line-of-sight path to the source point and storing the sinkpoints found, placing (21) diffraction points on all edges of a three-dimensional geometry, and building (24) a visibility matrix based on weighted paths for all source points and all sink points. The method can further include applying (25) a path finding algorithm on the visibility matrix for each sink point to all source points and storing store optimal paths for each source point to all sink points if they exist. The method can further include determining (23) if a last source point is selected before building the visibility matrix.