Résumé
This paper describes a technique that speeds up both the modelling and the sampling processes for a ramified object. By introducing the notion of substructure, we divide the ramified object into a set of ordered substructures, among which only a part of basic substructures is selected for implicit modelling and point sampling. Other substructures or even the whole object can then be directly instantiated and sampled by simple transformation and replication without resorting to the repetitive modelling and sampling processes.