In this talk I will discuss the numerical computation of polycrystals using narrow band level set methods. I will describe the application of this method to the computation of diamond thin films and MgO films grown using ion beam assisted deposition (IBAD). I will explain a simplified computational approach for computation of polycrystalline thin films with emphasis on IBAD MgO films. (This is joint work with X. Li, G. Russo, and D. Srolovitz)