IRCOM SIC, UMR 6615 CNRS
Boulevard 3 - Téléport 2 - BP 179
86960 Futuroscope Cedex, France
Global processing of diffraction phenomena by a half-plane was proposed by Aveneau and Mériaux, using the Geometrical Theory of Diffraction. In this theory, diffraction rays are emitted by diffraction points belonging to the half-plane edge (or dihedron edge). The solution given for finding these points being numerical, it is difficult to implement and leads to low precision solutions with a slow algorithm. In this paper we first propose a new geometric solution for finding the dihedron diffraction points, which leads to an efficient analytic algorithm. Next we present an implementation of a Ray-Tracing software for polygonal scenes with an automatic diffraction treatment. Since this implies diffraction by dihedra, we present the dihedron data structure and the corresponding algorithm which solves two problems : the existence of diffraction paths, and the impossibility for dihedra to share their edge. These elements lead to an implementation of a Ray-Tracing software with first diffraction account for any polygonal scenes.
Keywords : Rendering Techniques, Diffraction, GTD, Ray-Tracing.