Hi, I want to find the shortest ray path between two points diffracted by multiple 3D obstacles (represented by vtkPolyData). Can VTK do this? Otherwise does anyone know an alternative computational geometry library? Takuya OSHIMA, Ph.D. Faculty of Engineering, Niigata University 8050 Ikarashi-Ninocho, Nishi-ku, Niigata, 950-2181, JAPAN