Rockyfor3D is a simulation model that calculates trajectories of single, individually falling rocks, in three dimensions (3D). The model combines physically-based, deterministic algorithms with stochastic approaches, which makes Rockyfor3D a so-called ‘probabilistic process-based rockfall trajectory model’. Rockyfor3D can be used for regional, local and slope scale rockfall simulations. Rockyfor3D is continuously being used in research projects for testing, potentially leading toimprovement of model algorithms (cf. Bourrier et al. 2009). Nevertheless, for good results, Rockyfor3D requires consistent input datathat represents well the reality in the terrainand that correspondsto the scale of analysisadapted to the objective of your rockfall trajectory study (1-a regional hazard analysis, 2-a communal hazard analysis,or 3-a detailed hazard analysis for a single slope).