The modern world of computer graphics is mostly dominated by polygonal models. Due to their scalability and ease of rendering such models have various applications in a wide range of fields. Unfortunately some shape modelling and animation problems can hardly be overcome using polygonal models only. For example, dramatic changes of the shape (involving change of topology) or metamorphosis between different shapes can not be performed easily. The Function Representation (FRep) [Pasko et al. 1995] allows us to overcome some of the problems and simplify the process of the major model modification. Our system is based on a hybrid modelling concept, where polygonal and FRep models are combined together and can be evaluated in near-real or real time. It allows us to:

• produce animations involving dramatic changes of the shape (e.g. metamorphosis, viscoelastic behaviour, character modifications etc) in short times (Fig. 1)

• interactively create complex shapes with changing topology (Fig. 2) and specified level of detail (LOD)

• integrate existing animated polygonal models and FRep models within a single model