Smooth Surfaces and Sharp Junctions

Because of their ability to form blends, respond to contact and produce both organic shapes as well as man made objects, implicit surfaces have the potential for uses other than the traditional clouds and water droplets. Models can be built with either direct manipulation or through a procedural interface. A hierarchical skeletal implicit modeling system, the BlobTree, is described as a tool for the creation of a wide range of models. The differential properties of implicit surfaces are exploited to explore new techniques for rendering blobTree models in several pen-and-ink styles. An interactive system is also described that infers 3D models from sketched 2D outlines that combine basic shapes using standard blending and CSG operators. The underlying BlobTree enables far more complex models to be described, from cartoon-like characters to detailed mechanical parts, than was previously possible using a sketch based methodology.