1. A system for simulating a process step in manufacture of an integrated circuit device through a plurality of time increments, comprising: a memory; and a data processor coupled to the memory, the data processor configured to: represent a body with a three-dimensional bulk mesh, the bulk mesh identifying a pre-increment set of at least one materials interface; evolve the body by simulation through a time increment of the process step, the simulation identifying a post-increment set of at least one materials interface; represent each of the interfaces in the post-increment set of interfaces with a boundary mesh representation separate from the bulk mesh; smooth the boundary mesh representation of at least one of the interfaces in the post-increment set of interfaces; regenerate at least part of the bulk mesh in dependence upon the smoothed boundary mesh; and continue the simulation of the process step.