Accession Number:

ADP012054

Title:

Extensions: Extrapolation Methods for CAD

Descriptive Note:

Conference paper

Corporate Author:

HEWLETT-PACKARD LABS PALO ALTO CA

Personal Author(s):

Report Date:

2000-01-01

Pagination or Media Count:

9.0

Abstract:

Many operations within a solid modeling application, notably applying thickness shelling or blending edges filleting,encounter difficulties during topology resolution. In order to create a solid object, certain faces have to be intersected but the geometry is such that no intersection curve can be computed. The solution is to extend one or both faces. This means that one has to extrapolate the underlying curves or surfaces. This operation causes instability since extrapolation is inherently an unstable process. An additional difficulty is the selection of a strategy to compute the extension amount. Furthermore, there are additional restrictions relating to continuity across the extension boundary. In this paper I will illustrate by examples some modeling situations where extensions are necessary. I present the methods currently used, and illustrate their advantages and disadvantages. Subsequently, I will demonstrate a solution for primitives such as cylinders, cones, spheres and tori. I will conclude by suggesting approaches which could avoid some of the current pitfalls.

Subject Categories:

  • Numerical Mathematics
  • Theoretical Mathematics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE