Paradigms for the shaping of surfaces in a virtual environment

This paper describes several paradigms for the direct manipulation of a surface in computer graphics. The surface is considered as a collection of points in three-dimensional space. 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 and the definition of the weighted transformation is described. An interface for these paradigms in a virtual environment is also described