Virtual prototyping is the process of evaluating digital versions of designs without building physical mockups. Industry is increasingly turning to virtual prototyping in an effort to reduce design time and costs. The ability to evaluate various design configurations early in the design process using digital models allows for more opportunity to optimize the product design and explore alternate design configurations at a lower product design cost. This paper describes the development of virtual tools which give the designer the ability to take virtual prototyping one step further by allowing interactive modification to the virtual surfaces while in the virtual environment.
Virtual prototypes are created directly from computer aided design (CAD) data. Non-uniform rational B-splines (NURBS) have become the industry standard for representation of free-form curves and surfaces (Piegl, 1991). The contribution of the work presented here is in the development of virtual tools which are used to operate directly on the CAD data and change the shape of the NURBS surfaces in a virtual environment. The virtual tools can be dragged along or pushed into the surface in real-time to change its shape. The surface normal at an arbitrary point can be manipulated in three-dimensional (3D) space. Constraint-based surface manipulation is used to obtain multiple point direct manipulation of NURBS surfaces, which is not currently available in other VR CAD programs.