Thursday, November 6

On NURBS and Triangles

9:15 AM-10:00 AM
Chair: Helmut Pottmann, Technische Universitat Wien, Austria
Room: Belle Meade

Mature CAD/CAM technology exists to convert from design concepts to production-quality geometric models to physical parts. In this "forward" process, it is not unusual for various triangle mesh approximations to be computed for display and NC machining purposes, and then discarded. The corresponding "reverse" technology to convert physical parts to production-quality geometric models (to allow design modifications or computerized replication) is not nearly as mature despite advances in recent years. Further developments are needed to attain most of the potential productivity advantages.

A critical problem is representation. Production-quality geometric models usually consist of trimmed and untrimmed NURBS surfaces with carefully arranged topological and geometric relationships. When 3d points are acquired from physical surfaces, the output is points, polylines, or triangles at best. The conversion of this acquired data into production surfaces is still primarily manual and typically somewhat unfaithful to either the 3d point data, or the design intent, or both.

The speaker will delve into key problems in this reverse engineering area and discuss relationships to NURBS tessellators with specific focus on the nearly identical forms of surfaces tessellated to manufacturing tolerances and filtered triangle meshes derived from 3d scanner data.

Paul Besl
Alias/Wavefront, Inc.
Farmington Hills, Michigan

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tjf, 7/02/97