Direct haptic rendering of complex trimmed NURBS models

The most accurate haptic rendition of a virtual model is produced when the haptic algorithm acts directly on the actual model and not an intermediate representation. In the modeling and design communities the de facto model representation standard is NURBS. Further, more powerful systems provide trimming and adjacency information within the models representation. This additional information permits more complex models to be expressed succinctly but also increases the complexity of representation. In this paper we present an algorithm that supports direct haptic rendering of models constructed from trimmed NURBS surfaces. Our distributed system links an advanced modeling system to a force-reflecting device. In addition, we present extensions to the algorithm which support model manipulation, dimensioned probes, and multi-probe contact.