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第20届全国计算机新科技与计算机教育学术大会

作者： HAO Aimin 郝爱民 YANG Shuolei 杨硕磊 WANG Lili 王莉莉 State Key Laboratory of Virtual Reality Technology and Systems Beihang UniversityBeijing 100191 北京航空航天大学计算机学院虚拟现实技术与系统国家重点实验室北京100191

真实感图形生成通常采用的经典光照模型难以表达一些特定的光学现象。本文给出了一种基于物理频谱的光照模型，光源颜色不使用RGB值表示，而是采用其物理特性即频谱表示，并根据CIE提供的函数，设计了一种基于图形处理单元(GPU)的高效... 详细信息

真实感图形生成通常采用的经典光照模型难以表达一些特定的光学现象。本文给出了一种基于物理频谱的光照模型，光源颜色不使用RGB值表示，而是采用其物理特性即频谱表示，并根据CIE提供的函数，设计了一种基于图形处理单元(GPU)的高效转换算法，解决了模型运算量大的问题。将上述模型应用于虚拟光学物理实验中，模拟了光的折射、干射、衍射等现象。

关键词：计算机辅助教学虚拟实验光照模型物理频谱

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Complements to the Online Phase in the Horus System

Complements to the Online Phase in the Horus System

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ISECS International Colloquium on Computing, Communication, Control, and Management, CCCM

作者： Chengxiao Fang Xiaohui Liang State Key Laboratory of Virtual Reality Technology and Systems Beihang University China

Horus is an RF-based location determination system. It is currently implemented in the context of 802.11 wireless LANs. The system uses the signal strength returned from the access points to infer the user location. The signal strength of AP corrected in the online can not be found in the set of radio map sometimes. As result, we can not get the probability and infer the location of user. Papers about Horus tell nothing about it. This paper aims to give the reason and approach to deal with this phenomenon.

关键词： Wireless LAN Distortion Probabilistic logic History Radar tracking Wireless communication Robot sensing systems

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Physically-based detail-preserving algorithm for real-time deformation

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Jisuanji Yanjiu yu Fazhan/Computer Research and Development 2008年第3期45卷 503-509页

作者： Che, Yinghui Liang, Xiaohui Zhao, Qinping State Key Laboratory of Virtual Reality Technology and Systems Beijing 100083 China School of Computer Science and Engineering Beihang University Beijing 100083 China

Real-time deformation is one of the hot research issues in computer graphics and it is widely used in video games, virtual surgery and virtual reality. However, physically-based deformation can be computationally expensive, so the problem of real-time deformation for complex objects is yet to be solved. In this paper, a new method of real-time deformation is proposed, which integrates the advantages of physically-based deformation and multi-resolution mesh editing and works well with complex elastic objects. In the preprocessing stage, the algorithm simplifies the original detail mesh to generate a base mesh representation adaptively, and then encodes position and normal of the vertices of the detail mesh based on the base mesh. In the real-time rendering phase, the physically-based deformation is performed on the base mesh, and with the deformed base mesh and the encoding geometry details, the deformed detail mesh can be easily reconstructed. In order to improve the rendering speed, the rendering stage sufficiently utilizes the parallelism ability of graphics hardware and most calculation is executed by the fragment program. Experiments show that the method preserves the local details relatively well during the deformation procedure and it is suitable for the applications of real-time deformation of objects with complex surface details.

关键词： Computer graphics

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Avatar migration mechanism based on cell buffer

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Jisuanji Yanjiu yu Fazhan/Computer Research and Development 2008年第10期45卷 1654-1661页

作者： Zhou, Zhong Wang, Shaofeng Wu, Wei State Key Laboratory of Virtual Reality Technology and Systems Beihang University Beijing 100083 China School of Computer Science and Technology Beihang University Beijing 100083 China

Avatar migration which changes the resident server of an avatar is an important issue in distributed virtual environment. Existing methods for multi-server DVE (distributed virtual environment) systems mainly conduct avatar migration according to the relationship between the avatar's movement and servers' region buffer, and the region buffers are fixed. However, regions are often regulated to balance the load in the latest multi-server DVE technologies. Then affected avatars have to migrate during the period of region regulation. This avatar migration of dynamic region buffer needs further study. An avatar migration mechanism based on cell buffer is proposed in this paper, where each region buffer is composed of a group of cells. Both cell and avatar are assigned to some status. Avatar migration is induced by two kinds, either avatar movement or region regulation. The mechanism abstracts the two kinds into a process of four critical conditions of status migration. Migration operations are devised on the status of avatar and the cell it resides on. In this way, many avatars can migrate concurrently with efficiency. The attribute update request of an avatar is only put in its region server's charge, which guarantees the status consistency. Experiments show that the mechanism can support concurrent migration efficiently, adding a low communication cost.

关键词： Cells

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Layered iterative load balancing algorithm for distributed virtual environment

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Ruan Jian Xue Bao/Journal of Software 2008年第9期19卷 2471-2482页

作者： Wang, Shao-Feng Zhou, Zhong Wu, Wei State Key Laboratory of Virtual Reality Technology and Systems Beihang University Beijing 100191 China School of Computer Science and Technology Beihang University Beijing 100191 China

To support large-scale users to share a virtual environment, multi-server architecture is applied to the virtual environment system and each server handles a partition of the virtual environment. The unpredictable movements and interactions of avatars may cause some servers to be overloaded. Existing load balancing algorithms try to redistribute load among servers and incur too much overhead, which may reduce the interactivity of system. In this paper, a layered iterative dynamic load balancing algorithm is proposed. Setting the overloaded region as the center, the algorithm chooses a limited number of neighboring regions as the load adjusting goals and iteratively spreads the overload outward from the center. The load balancing state can be achieved through iterations. Based on the virtual environment wherein avatars are scattered under skewed and clustered distribution, the algorithm is built and comparison with the existing load balancing algorithms are made. The results show that this algorithm can adjust load efficiently and incur less overhead.

关键词： virtual reality

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Offset algorithm for Loop subdivision surface with creases

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Jisuanji Fuzhu Sheji Yu Tuxingxue Xuebao/Journal of Computer-Aided Design and Computer Graphics 2008年第10期20卷 1261-1265页

作者： Bai, Jie Zhao, Gang Yao, Fusheng State Key Laboratory of Virtual Reality Technology and Systems Beijing 100083 China School of Mechanical Engineering and Automation Beihang University Beijing 100083 China

The different levels of Loop subdivision surfaces could be used as the geometrical models for different procedures of the NC machining. Using the existing algorithms which did not consider the crease or the border, we may receive different results other than what we expect. Firstly, a method is presented to compute the limit offset positions for the sharp points. Secondly, the Gauss-Jacobi iterative formulas to compute the offset positions of the initial control points based on the limit offset positions are provided. At last, the astringency of the iterative formulas is proved. The results illustrate the feasibility of the methods.

关键词： Iterative methods

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Movement model for battlefield with confrontation characteristic

Movement model for battlefield with confrontation characteri...

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Asia-Pacific Conference on Communications

作者： Junxia Cai Wei Wu State Key Laboratory of Virtual Reality Technology and Systems Department of Computer Beihang University Beijing China

In this paper we propose a mobility model derived from real-time strategy gamepsilas replays which can reflect confrontation & collaboration characteristic of nodes movement in military scenario. This mobility model covers several unitspsila characters, including the velocity distribution, mutual synergies, creation/destruction and terrain effect. Game playerspsila human decision is also involved, which makes this mobility model completely different from previous ones. We analyze how the confrontation &collaboration characteristics are reflected in our mobility model. We also evaluate the AODV protocol on the proposed model and traditional Random Waypoint model, and simulation results show that the network performances and topologies are significantly different when different mobility models are adopted. According to these results, this model could generate more realistic simulation scenario than the traditional mobility model, and the simulation results are more credible.

关键词： Collaboration Military computing Protocols Game theory Network topology Costs Computer aided instruction Laboratories virtual reality Ad hoc networks

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A Level of Detail Selection Method for Multi-Type Objects Based on The Span of Level Changed

A Level of Detail Selection Method for Multi-Type Objects Ba...

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IEEE Conference on Robotics, Automation and Mechatronics

作者： Zhuo Yu Xiaohui Liang Zhiyu Chen State Key Laboratory of Virtual Reality Technology and Systems School of Computer Science and Engineering Beihang University China

Level of detail (LOD) selection method is a key component in complex scene rendering and is widely used in time-critical systems. Many studies focus their efforts on developing the LOD selection method to deal with the problem which the scene contains small objects or objects with a single type. This paper gives a LOD selection method handling the situation that the scene contains multi-type objects while the data amount of these objects change dramatically. The preprocessing step of our work is using the extreme simplification way to simplify the objects with large number of primitives and using the quadric error metrics to simplify the small ones. Then we calculate the span of level changed to each type of object separately. In runtime, we organize all the objects into a max heap by using the importance factor for rendering. We get the top element of the heap and change its level until the total data of objects satisfy the condition of time-critical method. Compared to existing solutions, our method is more suitable to the situation when the scene contains different type of objects.

关键词： Layout Time factors virtual reality Computer science Military computing Runtime Data acquisition virtual environment Application software Computer applications

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A collaborative virtual assembly system based on mobile devices

A collaborative virtual assembly system based on mobile devi...

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Computer systems Architecture Conference (ACSAC), Australasian

作者： Xiaohui Liang Zhiying He Xiaoxiao Wu State Key Laboratory of Virtual Reality Technology and Systems School of Computer Science and Engineering Beihang University Beijing China

Adding mobile devices to virtual environment and using them as interactive tool can enhance mobility and the sense of immersion. This paper researches on how to let multi-users work collaboratively through mobile devices in a virtual environment and develops a PDA-based collaborative virtual assembly system supporting multi-user participant. The system let users directly interact with virtual environment through the manipulation of the objects displayed on the PDAs, which makes interaction more intuitive. In this paper, we introduce the main modules of the system, including the data transmission service module and display/interaction module.

关键词： Personal digital assistants Servers Data communication Mobile handsets virtual environment Three dimensional displays Geometry

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A Multilayer Portal Model for Information Grid

A Multilayer Portal Model for Information Grid

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ChinaGrid Annual Conference (ChinaGrid)

作者： Xiaowu Chen Mingji Chen Xixi Luo State Key Laboratory of Virtual Reality Technology and Systems School of Computer Science and Engineering Beihang University Beijing China

ISBN: (纸本)9780769533063

Grid portal is the point of access to a grid system, it provides a friendly portal interface for grid users. Most computing grid uses grid portal to facilitate scientists to access computing resources through job submission, job monitoring, file transferring and so on. And information grid portal is to seamlessly get information for grid users, since information grid is a system that utilizes grid technology to implement information sharing, information management and providing information services. University digital museum grid (UDMGrid) is a typical system of information grid, whose portal is to seamlessly access digital specimens by a one-stop information service. With the developments of information grid, semantic Web and portal model, this paper presents a multilayer portal model for information grid. This model is composed of multiple layers, which include grid resource layer, grid service layer, portlet service layer, portlet layer, application service layer and user layer. The application and experiment of this multilayer portal model in UDMGrid demonstrate its usability, maintainability and expansibility.

关键词： Portals Ontologies Information services Nonhomogeneous media Visualization Semantic web Middleware

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