Rockfall is an increasing problem in many mountainous regions throughout the world. In Switzerland during the summer of 2015 we observed escalating rockfall activity due to exceptionally warm temperatures and degradation of permafrost. Consistent and reproducible calculation methods are urgently required to predict rockfall inundation areas for hazard mapping and mitigation measure planning. In this paper we examine the use of non-smooth contact/impact mechanics to model the trajectory of falling rocks. Non-smooth mechanics parameterize the mechanical resistance of ground with consistent frictional parameters. These parameters account for rock shape and different rock propagation modes such as rolling, skipping, jumping and sliding; enabling a the characterization of different ground types, varying from extra soft to extra hard. We apply the new method to back-calculate a well-documented rockfall event demonstrating the important role of ground parameterization and rock shape in rockfall intensity mapping.