中国古建筑风格初探(英文)(3)

model should be deflected from a fixed distance along z-axis,

and then every component returns to its original position along

z-axis in order.

The animation of 3DS MAX is based on key-frame technique.

The core of this technique is to fix the so-called key-frames, and

then let 3DS MAX software system to interpolate to generate those between key-frames. It can be used to carry out building’s

order of assembly, but interval among key frames and distance

of movement (or angle of rotation) together will affect speed of

the animation, so preparation of script is very important to control animation process.

Insert frame among key frames Figure 13 key-frame technique

The attribute values of key frames will be stored in a structure

named curve node and will be controlled by the node, and speed

of the animation can be adjusted by the tangent of a curve. It

means that, if error of assembly order happened, adjustment of

key frames will affect speed of the animation, so it is a good idea to save a middle file every other thousands frames.

By setting key frame of camera, movement, rotation, material and so on, rich outcomes will be gotten. In order to display such

kind of construction art, a human-computer interaction visible environment can help users make sense of components’ structure and function as well as browse building and building

group dynamically. If needed, multimedia technique is another

good idea, which can make outcomes more interesting and transparent.

3.3 Collision Detection

Because of mechanical processing error of timber component, timber deformation and error in design, unmatching in component position or size will be possible at the assembly spot. In fact, simulating assembly process is not only a displaying process of building constructing technology but also a test process for components position and size. Hence there have the following three reasons for collision detection when computer simulating assembly takes place: to detect whether collision happens between models, to report the place where there is already or will be a collision and the distance between dynamic Query model.

The initial motise-tenon connection algorithm is to do pairwise intersection test for all the basic geometrical elements in two input models. If there are n polyhedrons in virtual scene, m pinnacles for every polyhedron, the complicate degree of time

of the collision detection will be 0(N 2M 2

), to the disadvantage

of real-time interaction. Reducing the amount of pairwise intersection test of basic geometrical elements, speeding up algorithm to assure real-time interaction in virtual environment are the cores for motise-tenon connection algorithm. Commonly used connection algorithm for

the moment can be classified into two kinds: spatial decomposition and hierarchical bounding boxes.

Typical spatial decompositions are OCTREES, BSP tree and so on. For the sake of large memory and inflexibility, they are not

used as widely as bounding box hierarchical approach. According to difference in bounding boxes, bounding box hierarchical approaches can be divided into AABB(axis-aligned

bounding boxes) ??OBB(oriented bounding boxes)??DOP (discrete orientation polytopes, K-DOP is called FDH (fixed direction convex hull)) and etc. AABB is not closely knitted, but intersection test between AABB is simple, OBB is closely knitted caused by OBB arbitrary direction, but its intersection test is complicated; FDH goes between the two, its characteristic is that as long as reasonably selecting the number

and direction corresponded with parallel plane, a flexible selection can be made between simple connection and close knitted packing object, namely, it is superior to AABB in knitting, it’s not as complicated as OBB in intersection test, its

complex function is the best. As for collision test of rigid bodies, judgment of function is based on OBB connection

algorithm.

For n components in timber-structure building’s 3D model, in

most real environments, they can only with few approximating objects, there is no such necessity to do motise-tenon connection for all components and it is a waste of time to do so. Before collision detection, preselection can be done such as using sweep and prune algorithm to decrease the number of objects that will be done the connection. Timber-structure

building has discernible hierarchical structure, a simple way is to use orthographic projection, that’s, project object-compatible-volume onto coordinate surface (such as surface x and y), then use rectangular filing ordering algorithm to do selection, and finally verify whether overlapping rectangles have intersected with its projection on another coordinate axis (axis z).

Because of complication in assembly process and problem caused by massive data, using single detection method can’t

meet requirements. This paper will deal with it in four steps in terms of characteristics of timber-structure building: 1. motise-tenon connection preselection

2. use AABB, to do sketchy connection for most components, ruling out those objects that are far away and have not connected

3. using FDH or OBB’s hierarchical structure to do accurate connection 4. doing initial connection

Figure 14 process of simulating assembly

Timber itself is different from other materials; it has a certain degree of elasticity. Components’ partial and hierarchical spot assembly detection is an indispensable link, and it should be taken into consideration together with computer simulating assembly as an integration.

The result of assembly is showed as followed (figure 15).It can

supply direction for reconstruction of ancient buildings.

Figure 15 the result of building assembly

4. CONCLUSION AND FUTURE WORK

Computer technology, virtual technology is of vital importance to protection of cultural relics and historical sites such as ancient buildings. Through components modeling by computer, hierarchical assembly and integrated assembly, the purpose of examining and accepting project quality can be achieved. It is a new modal for overall quality management with high efficiency, overall, and low cost. By establishing database to preserve architectural file, architectural research and provide necessity for building’s recover and reconstruction. And it can be and explored used for the second time based on that.

In future work, we are aiming to apply similar techniques for ancient buildings’ preservation and recovery, project quality control and 3D reconstruction. An integration of 3D geographic information systems (3DGIS) and computer-aided design (CAD) would provide newer forms and better ways. In addition, we are seeking better understanding of integrating architectural art with computer technology for heritage recording purposes. This includes developing new tools and methods to streamline the digital recording process.

ACKNOWLEDGEMENTS

The authors would like to express the most sincere gratitude to Chi Lin Nunnery for giving us the precious chance and providing us abundant data and information. At one time??We would like to thank those veteran workers from Anhui province in China ,and they give us a lot of good advice. The other members of our workgroup are Yang Yuan, Qing Zhan, Ruiju Zhang, Jianhong Cai, Song Xia, Qingshun Li, Liang Chen,and the authors would like to thank them for their effort and many excellent ideas.

REFERENCES

Deren Li, Jie Yang, Yixuan Zhu, 2002: Application of Computer Technique in the Reconstruction of Chinese Ancient Buildings, Proceedings of the ISPRS commission V symposium, September 2-6, 2002, Corfu, Greece, Intern Qing Zhu, Hui Lin, 2003. Digital City Geographic Information System, pp.62-82.

Feng Dong, Tongyang Wang,2004. Rapid Collision Detection Algorithms in Virtual Environment.

Chunxiao Gao, Yushu Liu, 2003. A Survey of Collision Archives of P&RS Volume XXXIV, Part 5 Comm.V.404-406 Miaozhong Xu, Yixuan Zhu, 1998, Computer-Based Simulation and Quality Control for Building, Working Group V/5, ISPRS, pp. 252-258.