Shared virtual worlds require exchanging shape models over the Internet. Since complex shapes such as VRML objects are often defined with polygonal meshes, the size of models may become very large. It slows down their visualization and limits the model's precision. Using function-based models incorporated into VRML or other visualization frameworks allows for reducing the overall size of models as well as provides any required level of detail. In this paper, we propose a fast function-based shape modeling framework. The developed software is used for collaborative shape modeling in VRML shared virtual worlds. It allows for passive visualization of the complex function-based models in cyberworlds as well as for their interactive modeling.