Abstract:
This paper describes a system for the representation and
rendering of polyhedral scenes in which individual
components can have different user-specified amounts of
rounding applied to edges and corners. Objects are
represented by structures similar to CSG trees but with
arithmetic operators at internal nodes rather than set
membership operators. An object’s smoothing attribute
specifies the radius of a spherical smoothing filter, and
the smoothed object’s surface is defined by an iso-density
surface after low-pass filtering. The filtering is an
approximation to true convolutional filtering, but allows
rapid determination of iso-density surfaces. The rounded
surfaces are similar to those achieved by use of filleting
and surface blending techniques during modelling, but are
much easier to specify, far more economical in storage,
and simpler to compute. By varying the smoothing radii,
a wide range of effects can be obtained, from near-perfect
polyhedra through to “blobby models”.