X-ray topography, particularly using synchrotron radiation has been key in characterizing and analyzing defect behavior in silicon carbide crystals from bulk growth through epilayer growth and device fabrication [1]. Understandings from these studies have contributed significantly to optimization of silicon carbide crystal growth to lower defect densities and improved performance of power devices. Rapid imaging and characterization of defects in silicon carbide crystals using X-ray topography has been greatly enabled by use of defect image simulations using the ray-tracing simulation technique [2]. Ray tracing simulation is based on the orientation contrast mechanism that has been shown to dominate contrast of defects observed on actual X-ray topographs. In this review, development of ray tracing simulation technique and its application to characterization of defects in silicon carbide crystals is discussed. The principle of ray-tracing simulation is introduced (Fig. 1) and simulated dislocation images such as micropipes, threading screw and mixed dislocations (TSD/TMD), threading edge dislocations (TEDs) and basal plane dislocations (BPDs) are compared with experimental images (Fig. 2) [3]. Recent developments such as incorporating the effects of surface relaxation and photoelectric absorption to simulate different dislocations more realistically is discussed in both 4H-SiC as well as 6H-SiC crystals of various orientations. By incorporating the incident beam characteristics as well as the rocking curve of operative reflection, ray tracing simulations has also been adapted to simulate dislocations images recorded by weak beam topography [8] and plane wave topography [9]. A detailed investigation of effective penetration depth of all types of dislocations lying on the basal plane on grazing-incidence X-ray topographs is also presented [3]. Future developments of this indispensable tool for X-ray topography include extending its application to laboratory X-ray sources will be discussed. [1] B. Raghothamachar, M. Dudley, in Wide Bandgap Semiconductors for Power Electronics: Materials, Devices, Applications (P. Wellmann, N. Ohtani, R. Rupp, eds.) pp 169-197, 2022 WILEY-VCH GmbH. [2] X. R. Huang, M. Dudley, W. M. Vetter, W. Huang, W. Sia, C. H. Carter Jr., J. Appl. Crystall., 1999. 32(3): p. 516-524. [3] Q. Cheng, Z. Chen, S. Hu, Y. Liu, B. Raghothamachar, M. Dudley, Mater. Sci. Semicond. Proc., 174, 108207,(2024). https://doi.org/10.1016/j.mssp.2024.108207 [4] X. R. Huang, M. Dudley, W. M. Vetter, W. Huang, S. Wang, C. H. Carter, Jr., Appl. Phys. Lett, 1999. 74(3): p. 353-355. [5] Chen, Y., M. Dudley, Appl. Phys. Lett., 2007. 91(14): p. 141918. [6] I. Kamata, M. Nagano, H. Tsuchida, Yi. Chen, M. Dudley, J. Crystal Growth, 2009. 311(5): p. 1416-1422. [7] Huang, X.R., D. R. Black, A. T. Macrander, J. Maj, Y. Chen, M. Dudley, Appl. Phys. Lett., 2007. 91(23): p. 231903 [8] H. Peng, T. Ailihumaer, Y. Liu, B. Raghothamachar, X. Huang L. Assoufid and M. Dudley, J. Appl. Cryst. 54(4): p. 1225-1233. [9] H. Peng, Z. Chen, Y. Liu, B. Raghothamachar, X. R. Huang, L. Assoufid, M. Dudley, J. Appl. Cryst. 55, 2022. 55(3): p. 544-550.