Paradigms for the Shaping of Surfaces in a Virtual Environ- ment

This paper describes several paradigms for the directly manipulating a surface in computer graphics. The surface is considered as a collection of points in three-dimensional space which define a surface. These points may be the vertices of polygons, the control points of splines, and so on. Three paradigms are described and evaluated: direct grabbing of the surface at a single point and moving a neighborhood of that point; pushing on the surface with a tool; and pushing on the surface with a model of the user's hand. These paradigms are based on a spatially weighted transformation. This transformation is based on a 'bump' weight function on the surface which is shaped and placed by the user. Construction of the bump function is described and the definition of the weighted transformation is described. The use of the weighted transformation in each paradigm is also described. These paradigms are implemented on a virtual environment system based on a Fake Space BOOM for display and a VPL Dataglove Model II for manipulation. The computation and rendering platform is a Silicon Graphics 380GT/VGX. ______________________ † Employee of Computer Sciences Corporation. Work supported under government contract NAS 2-12961