Surface modeling
Surface modeling defines not only the edge of the 3D object but also its surface. In surface modeling, two different types of surfaces can be generated: faceted surfaces using a polygon mesh and true curve surfaces. NURBS (nonuniform rational B-spline) is a B-spline curve or surface defined by a series of weighted control points and one or more knot vectors.
It can exactly represent a wide range of curves such as arcs and conics. The greater flexibility for controlling continuity is one advantage of NURBS. NURBS can precisely model nearly all kinds of surfaces more robustly than the polynomial-based curves that were used in earlier surface models. The surface modeling is more sophisticated than wireframe modeling. Here, the computer still defines the object in terms of a wireframe but can generate a surface ‘‘skin’’ to cover the frame, thus giving the illusion of a ‘‘real’’ object. However, because the computer has the image stored in its data as a wireframe representation having no mass, physical properties cannot be calculated directly from the image data. Surface models are very advantageous due to point-to-point data collections usually required for numerical control (NC) programs in computer-aided manufacturing (CAM) applications. Most surface
modeling systems also produce the stereolithographic data required for rapid prototyping systems.
Emory W. Zimmers, Jr. and Technical Staff
Enterprise Systems Center
Lehigh University
Bethlehem, Pennsylvania
Mechanical Engineers’ Handbook: Materials and Mechanical Design, Volume 1, Third Edition.
Edited by Myer Kutz
Copyright 2006 by John Wiley & Sons, Inc.
Enterprise Systems Center
Lehigh University
Bethlehem, Pennsylvania
Mechanical Engineers’ Handbook: Materials and Mechanical Design, Volume 1, Third Edition.
Edited by Myer Kutz
Copyright 2006 by John Wiley & Sons, Inc.
