CAD tools for aesthetic engineering
Introduction
In this tutorial, we are concerned with computer-aided design tasks in which the final evaluation is mostly based on aesthetic criteria. While most engineers accept the fact that one needs to use computers to design jet engines, computer chips, or large institutional buildings, it is less clear whether computers are also useful in the design of artifacts that are judged mostly by their looks. In a traditional CAD setting, the computer primarily serves as a precise drafting and visualization tool, permitting the designer to view the emerging geometry from different angles and in different projections. A digital representation also makes it possible to carry out some analytical tasks such as determining volume or surface area of a part.
We will show that today the role of the computer goes much further. It actively supports the creation of geometric shapes by procedural means and can even optimize a surface by maximizing some beauty functional. It further can help to extend visualization aids for complex parts through the generation of rapid prototypes on layered manufacturing machines. Finally, it may even amplify the creative process itself by allowing the designer to quickly explore a much larger domain of design alternatives.
The objects used as examples in this tutorial are mostly abstract geometrical sculptural forms or mathematical visualization models (Fig. 1). However, the principles and techniques discussed are readily applicable also to consumer products, or automotive parts and shapes. Creating maximally satisfactory forms for mathematical models or for geometric sculptures poses quite different requirements and constraints for any CAD tool than developing an optimized airplane wing or designing the most powerful computer chip. Real-time interactivity becomes a crucial factor, when a designer's eye is the key evaluation instrument in the design loop.
This tutorial overview starts by looking at some generic tasks in curve and surface design, in particular, ongoing efforts for defining a beauty functional for procedurally optimizing shapes that are only partially constrained by the designer. It then discusses some research aimed at finding efficient implementations and approximations of such optimization functionals, so that they can be used at interactive design speeds. Next, we look a parameterized design paradigm that allows an artist to rapidly explore and compare many alternative versions of a geometrical shape. Finally, we make the point that a CAD tool that is well matched to the task at hand is much more than just a ‘drafting assistant’ and can indeed become an amplifier for one's creative spark.
Section snippets
Optimization of smooth surfaces
Smooth surfaces play an important role in engineering and are a main application for many industrial CAD tools. Some surfaces are defined almost entirely by their functions; examples are ship hulls and airplane wings. Other surfaces combine a mixture of functional and aesthetic concerns, e.g. car bodies, coffee cups, flower vases, etc. Finally, for some cases, aesthetics dominates the designer's concern, for instance in abstract geometric sculpture.
Fair curves on fair surfaces
A second key CAD problem is the embedding of beautiful or fair curves onto the kind of optimized surface discussed above. For instance, one may need to draw a fair connecting line between two points on a smooth surface. The most direct such connection is a geodesic line, which exhibits no gratuitous lateral curvature. While it is easy to trace a directional geodesic ray on a smooth surface or on a finely tessellated polyhedral approximation thereof, it is a well-known hard problem to connect
Parameterized shape generation
The design and implementation of geometrical sculpture is a relatively novel application domain for CAD, in which the techniques outlined above would be particularly useful. In 1995, I started to collaborate with Brent Collins, a wood sculptor who creates fascinating abstract geometrical shapes [3], [4], [8]. His work can be grouped into cycles that have a common recognizable constructive logic to them, and which exhibit a timeless beauty that captured my attention immediately when I first saw
CAD tools for aesthetic design
The utilities described in this paper exist in a research environment but have not yet made it into main-stream commercial CAD tools. What might the future of such tools look like?
Conclusions
Computer-aided design tools are gradually also becoming more suitable for aesthetic engineering and for artistic shape optimization. Subdivision surfaces are being introduced to commercial CAD tools, and systems for exact evaluation and for optimization of such surfaces with a variety of tailor-made energy functionals have been demonstrated in research labs. Computers are now powerful enough to subject this shape to various simulations, ranging from simple stress analysis to the evaluation of
Acknowledgements
I would like to acknowledge the technical contributions by Pushkar Joshi and by Ling Xiao to the prototype CAD tools discussed in this paper. This work was supported by MICRO research grant 03-077, ‘Collaborative Design Environment’, and by the CITRIS Institute, one of the California Institutes for Science and Innovation (CISI).
Carlo H. Séquin is a professor of Computer Science at the University of California, Berkeley. He received his PhD degree in experimental physics from the University of Basel, Switzerland in 1969. His subsequent work at the Institute of Applied Physics in Basel concerned interface physics of MOS transistors and problems of applied electronics in the field of cybernetic models. From 1970 to 1976 he worked at Bell Telephone Laboratories, Murray Hill, NJ, on the design and investigation of
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Carlo H. Séquin is a professor of Computer Science at the University of California, Berkeley. He received his PhD degree in experimental physics from the University of Basel, Switzerland in 1969. His subsequent work at the Institute of Applied Physics in Basel concerned interface physics of MOS transistors and problems of applied electronics in the field of cybernetic models. From 1970 to 1976 he worked at Bell Telephone Laboratories, Murray Hill, NJ, on the design and investigation of Charge-Coupled Devices for imaging and signal processing applications. At Bell Labs he also got introduced to the world of Computer Graphics in classes given by Ken Knowlton. In 1977 he joined the faculty in the EECS Department at Berkeley. He started out by teaching courses on the subject of very large-scale integrated (VLSI) circuits, thereby trying to build a bridge between the CS division and the EE faculty. In the early 1980s, jointly with D. Patterson he introduced the ‘RISC’ concept to the world of microcomputers. He was head of the Computer Science Division from 1980 to 1983. Since then he has concentrated on computer graphics, geometric modeling, and on the development of computer-aided design (CAD) tools for circuit designers, architects, and for mechanical engineers. During the last 5 years he has collaborated with P. Wright in Mechanical Engineering on the CyberCut/CyberBuild project with the goal to streamline the path from creative design to rapid prototyping. Séquin's work in computer graphics and in geometric design have also provided a bridge to the world of art. In collaboration with a few sculptors of abstract geometric art, in particular with Brent Collins, Séquin has found a new interest and yet another domain where the use of computer-aided tools can be explored and where new frontiers can be opened through the use of such tools. Dr Séquin is a Fellow of the ACM, a Fellow of the IEEE, and has been elected to the Swiss Academy of Engineering Sciences.