COMPUTER AIDED DESIGN OF MING CHAIR

Dr. Zhang Kun, Prof. Wang Bo Wei

Tongji University, Shanghai, China

e-mail: doctorkun@hotmail.com

Abstract

Elegant and ingenious Ming chair has gained an important place in the world of furniture, there are many beautiful chair styles and this paper proposed an idea that by the aid of computers, we can study the possible combinations of existing styles and may design new and beautiful chairs. This paper also realized several interesting deformations based on the combination results. The deformation is not just for fun but can be seen as a approach to stimulate the designer’s creativity.

1. Ming Chair

Ming dynasty (1368-1644) is a period during which Chinese furniture manufacturing has reached the zenith of aesthetic. The flourishing of furniture manufacturing was due to the stable political situation, overseas trade and demanding for fine furniture. Ming furniture was made mainly in Su Zhou City and its outskirts. Su Zhou City is located near Chang Jiang River and is not far from sea, so it is easy to import precious timbers from south-east Asia, these precious timber such as rosewood, cedar, ebony are very good raw materials to make furniture. By the cleverness and exquisite craftsmanship of ancient Chinese people, precious timbers were changed into elegant, ingenious and unornamented furniture.

Ming furniture includes chairs, beds, tables, cabinets, racks and screens. This paper studies chairs. Ming chair is divided by Chinese scholars into four categories: high-back chair, horseshoe chair, folding chair and armchair. The difference between high-back chair and armchair is that high-back chair has no armrest. The name of horseshoe chair comes from the shape of crest rail and armrest, these two parts merged together and the shape looks like a horseshoe. Folding chair’s front legs and back legs crossed and the chair can be folded. Figure 1 shows the four kinds of Ming chairs: from left to right, they are high-back chairs, armchairs, horseshoe chairs and folding chairs.

Figure 1. Four categories of Ming chair

Chair is a very important furniture, it supports people in the daytime, allowing people to read, write and talk in a comfortable posture. It could be say that chair is a symbol of civilization, so it is essential for mankind to produce good chairs both in quality and aesthetic. In modern society, it is easy for us to produce good quality chairs because we own assembly lines, and we can find good timbers. But it is not easy to satisfy the need of aesthetic, since different people have different aesthetic that is a matter of philosophy, culture and history. The fact is Ming chair has a good reputation for its beauty and is loved by people around the world. We believe that Ming chair contains both good quality and high level aesthetic, it is a source of creativity for modern furniture design.

2. Computer aided design of Ming chair

A chair can be divided into smaller parts, for example, crest rail, armrest, splat, stile and so on. This paper’s aim is to study these sections, find their features and reunite them, and then to create new styles of Ming chair.

The approaches consist of three steps. The first step is to disassemble chairs, study every style of each part. Of course, it does not mean to disassemble a true chair, it is a work done in the mind. Through this step we learned that Ming chair has beautiful contour lines, there are straight lines and curved lines. Curved lines have two main shapes: S-shape and C-shape. We believe that curved line was designed both for practical purpose and decoration purpose. A curved splat is more suitable for people to lean against, and a curved crest rail is more beautiful than straight one.

The second step is to build 3D models for these chair parts. 3D model is good for visualization, it looks like a real one and user can view the model from every angle. We used 3D modeling software to build these models. Although there are many tools for modeling, experience and “craftsmanship” are also needed because the shapes ought to imitate the Ming chair best. The completed 3D models are stored in a database which will be accessed by a program later.

The last step is assembles a new chair by gluing all parts of the chair together. This task is finished by computer program, the user only need to select which style he wants for every part; for example, user can select a curved armrest or a straight armrest. This paper has developed a program that fulfills the last step. Figure 2 shows the interface of the program.

Figure 2. The program interface

This interface provide five chair parts for selection, they are crest rail, stile, splat, armrest and armrest bracket. Each part has two or more styles represented with icons. User can choose only one style of each part, and every part has a default style. The program will automatically “glue” these parts together according to the user’s selection. It can be seen from the interface that there are two possible crest rails, two stiles, two splat two armrests and three armrest brackets, so, the possible results is 2 ×2×2×2×3, that is 48 results. If there are more styles for each part, there will be more possible combinations. For simplicity reason the program does not consider the selection of other parts. Figure 3 shows four glued chairs.

Figure 3. Four “glued” Ming chairs

To make the results more interesting, this program adds four deformations to the chair model, they are scale, taper, bend and stretch. The degree of each deformation can be controlled by parameters. Scale deformation has three parameters, they are x factor, y factor and z factor, x, y, z means three directions in the coordinate system. The factor was given a random value, so the result is different each time. The first chair in figure 4 shows the scaled result.

Figure 4. Chairs after deformation

Taper deformation has three parameters: primaryaxis, amount and curve. In the program, primaryaxis is z, curve is -1.5 that gives the outline a curvy look, and amount is a random value that ranged from 0.5 to 3.5. In fact, parameter curve could also be set to random, but the result would be more unpredictable. The second chair in figure 4 shows the tapered result.

Bend deformation could produce interesting result. In figure 4, the third model looks like a rocking chair. The bend degree is controlled by the parameter angle. There are other parameters to control the deformation such as direction, but our program just ignored them and used the default value.

The above three deformations method have a common ground that they affect the whole chair model, while stretch deformation only affect parts of the chair. In the program, stretch deformation only adds to legs and stiles. Like the last chair shown in figure 4.

3. Conclusion

We have seen what this program can do, in fact, we can expect this program to do more things. For example, let program select the chair parts automatically without the user’s interaction, and produces a sequence of new style chairs. User can choose the most beautiful chairs from the sequence, or, in the future, the program will have the ability to judge which chair is the most beautiful one. Then there emerges a question: does computer can do the design work instead of human being?

We know that computer is becoming more and more clever, it can play chess with the champion. We believe that one day it may do design works by itself, this is really a challenge dream. Please look at the chair in figure 1, we noticed that the side pedals are higher than front pedal, the back pedal is higher than side pedals, it just like a stairs. This kind of pedals has a very interesting Chinese name “Bu Bu Gao”, which means step more and more higher. It is a hint that person, who sit on this chair is likely to make progress step by step, for example be promoted to higher and higher positions. We believe that the studies of computer designs will also get progress step by step in the future.

References

[1] Celestino Soddu, “La Citta’ Ideale” Generative Codes Design Identity, GA2002 Proceedings, 2002

[2] Wang Shi Xiang, “Appreciating of Ming Furniture”, San Lian Publisher of HongKong, 2001