The implicit surface modelling technique can be used to model “soft” objects, objects whose surface or topology changes over time. It offers the opportunity of modelling and animating relatively complex shapes using only a few primitives. The final object is constructed by blending the primitives, and as the primitives are moved the blended surface changes shape. This can cause problems with object appearance and consistency and unwanted blending of object parts. In this paper we describe work in progress which addresses these problems.