In this paper, classical uniform theory of diffraction (UTD) and its extension to multiple transition edge diffraction, slope UTD, is discussed. A 2-D ray tracing algorithm based on slope UTD is introduced. Trade offs between accuracy and computation time of slope UTD algorithm is discussed for multiple transition zone diffraction. To reduce computation time of slope UTD with reasonable error, further improvements based on convex full constructed via Fresnel zones is proposed. Preliminary simulation results are presented for the improved slope UTD algorithm.