Soft-sphere particle dynamics simulations have found wide use in recent years. One application for which this technique is particularly well suited is that of granular mixing. Particle properties can be varied on a particle-by-particle basis and detailed mixed structures are easily captured and visualized. While this method has proven to be quite versatile, it is computationally intensive. Current particle dynamics simulations in the literature generally handle 3000-5000 particles, whereas a typical industrial mixer may easily contain as many as 10(9) particles-six orders of magnitude more. However, in certain circumstances-such as in a tumbler mixer, where the bulk of the particle motion consists of a solid body rotation-it is not necessary to explicitly calculate the motion of all of the particles. By combining particle dynamics and geometrical insight, in essence, by focusing the particle dynamics simulation only where it is needed, a new hybrid method of simulation, which is much faster than a conventional particle dynamics method, can be achieved. This technique can yield more than an order of magnitude increase in computational speed, allowing simulations of the order of 10(4) particles, while maintaining the versatility of a particle dynamics simulation. Two applications of this technique are presented : a tumbler operated in the avalanching regime and a continuously flowing tumbler.