Summary: Explosions are among the most common special effects employed in the entertainment industry. Producing real explosions, however, is costly and potentially dangerous and special effects technicians have been turning to software to generate explosion sequences. Software tools typically allow artists to re-create the appearance of an explosion but ignore physical processes. More accurate techniques, used in scientific research, produce physically correct results but demand substantial computational resources and do not provide support for artistic expression. This paper discusses an explosion animation system, X-Sim, that incorporates physical principles relevant to the generation of an explosion in a compressible medium. Diverse explosion effects can be created automatically while still allowing the animator to adjust the processes involved. Computational issues concerning X-Sim are addressed and a multiresolution scheme is introduced that focuses computation on turbulent regions of the environment. Results generated with X-Sim, evaluated qualitatively and quantitatively, indicate that the system can generate explosion phenomena with reasonable accuracy. Animations produced with this system also point to its flexibility and utility.