In cases of densely occluded urban scenes, it is effective to determine the visibility of scenes, since only small parts of the scene are visible from a given cell. In this paper, we introduce a new visibility preprocessing method that efficiently computes potentially visible objects for volumetric cells. The proposed method deals with general 3D polygonal models and invisible objects jointly blocked by multiple occluders. The proposed approach decomposes volume visibility into a set of point visibilities, and then computes point visibility using hardware-visibility queries, in particular HP-occlusion-test and NV-occlusion-query. We carry out experiments on various large-scale scenes, and show the performance of our algorithm.

The modeling of large-scale vernacular houses in South-east China is a challenging work. In this paper, we implement an urban modeling system, using a production-based recursion grammar system to generate all the vernacular houses and the arrangement of the urban district. This grammar system is found on the basic elements of the vernacular houses' components, such as windows, gates, walls, roofs etc, which is regarded as a term in productions. Furthermore, to avoid the disadvantage (hard to control) of the grammar system and to ensure the coherent architecture styles of ancient vernacular houses, we also design a verifying system, which can check out those invalid house combination and regenerate them.

The management of dynamics objects is significant to VR systems, especially its data management, which plays an important role in the efficiency and reality of the systems. By separating and classifying the position, orientation, geometry structure and other relative attributes of moving objects into static and dynamic categories, different methods are used to process them. Generally, two steps are taken. First, we set up the static model of the objects, and then add dynamic attributes to them to make them dynamic. This paper pays more attention to dynamic attributes, especially spatial state time series, which may take various forms when stored in database. A compression algorithm, Hyper-Rectangle Compression (HRC), is introduced to avoid over dilating of the storage space with rapid growing time series data.

In this paper we describe an approach to the procedural techniques of pattern generation to be used in rendering, based on genetic algorithms. Procedural textures exhibit many advantages over traditional surface texturing techniques, but unfortunately it is difficult for us to find the correct procedural texture and appropriate parameters to create the desired texture can be a daunting task for even the most experienced user. Upon analysis of genetic programming techniques and image matching evaluation scheme, we attempt to generate procedural 3D cloud texture automatically.

During the process of the real object virtualization, the data obtained from the digital system, such as the three-dimension imaging and modeling system (3DIMS), are very large. Even after the processing based on reverse engineering, the resulting image still can't satisfy the demands of computer animation, etc. So a novel approach based on data reduction and subdivision is presented in this article. The experiment results are also given to show the effectiveness of proposed method.

This paper proposes a method to analyze numerically the excited modes for a cleaning tub model of small size. The vibration mode is caused by vibration of the cleaning tub that concentrates on the surfaces of tub walls connected with the surfaces of the water. This mode does not contribute to cleaning directly. On the other hand, the sound mode (named E mode) is the state that large sound pressure can be observed at most areas of the cleaning tub. The distribution of E mode is ovoid. The resonance frequency of E mode depends on the size of the cleaning tub, the thickness of the tub walls and the material of tub walls. We have also investigated the influence when the driving vibrator put to the bottom of the cleaning tub is working. It has been found as to E₁₁₁ mode that the sound mode nearby the bottom approaches to the sound mode when the bottom is rigid body.

In recent years, simulating natural phenomena has always been one of the most challenging tasks in computer graphics. As one of its most important parts, simulating wave has been given more and more attention. One method simulates wave by trying to solve the Navier-Stokes. Another method tries to start from the energy spectrums of wave, and then generates the model of wave. In this paper, we present an improving wave profile function to model the shape of wave. The results show that this method can fast and effective simulate wave.

This paper presents a new Monte Carlo computational way for solving global illumination problem. In this way, plenty of unbiased estimators can be employed to enrich the solutions so as to lead to simple error control and to speed up the estimation. The implementation of a so-called potential tracing algorithm on the basis of the new scheme has been carried out. Results, which have been obtained by rendering test scenes, show that this new framework is promising.

As the pop topic in geometry, triangulation is the elementary mathematical model in three-dimension data visualization. In this paper, a method for Delaunay triangulation using a uniform grid has been put forward. This method ensures the validity of determining the first side of triangulation and gives a fast method for determining the optimum point. This method ensures the correctness of triangulation and searching point strictly. Using the water-depth data, which is saved in Electronic Navigation Chart, has teted the simulation, and it proved that this method plays a very important role in the construction of the terrain of seabed.

Topological line-region relations are generally defined by DE-9DIM in GIS. But some distinguish topological line-region relations cannot be identified in DE-9DIM. In the paper, Segmental operator model is introduced to solve this problem. Let a region A filter a curve L and produce a set of sub curves within the exterior, the interior or the borders of A. The topological relations between a sub curve and A can be mapped into eight categories: across, cutsinto, along, ringof, around, sticksto, inside and disjoint. Segmental operator model is based on counting the number of sub curves that belongs to each of the eight categories. Any topological relations defined in DE-9DIM can be expressed in segmental operator model when knowing whether A has holes or not. In segmental operator model, L is atomic to A when only a single sub curve is produced, simplex to A when all sub curves belongs to the same category, or L is complex to A.

A new method of calculating discrete curvature on digital curves is proposed based on Taylor's theorem. The method first determines the region of support for each point based on its local properties, then computes its curvature absolute value according to the vector accumulation. The vector is formed by the point and the middle point of a moving chord. It can be applied to both planar and space curves. Experimental results with simulated and real images show that this method is simple and robust, and can represent the features of digital curves.

Image mosaic is comprised of building a large field of view from a sequence of smaller images. It can be performed by registering, projective warping, resampling and compositing a serials of images. Due to the many possible factors for color and brightness variations when taking images, it is possible to lead to misalignment and obtain poor stitching result. Despite image mosaic can be manually adjusted using some photo editors like PhotoShop, this is not only tedious but also requires skills, knowledge and experience. Automatic adjustment is therefore desirable. By converting images to lαβ space and applying a special statistical analysis, color and brightness correction can be done automatically and improved image mosaic can be obtained.

The principle to construct G&IBMR virtual scene based on stereo panorama with binocular stereovision was put forward. Closed cubic B-splines have been used for content-based segmentation to virtual objects of stereo panorama and all objects in current viewing frustum would be ordered in current object linked list (COLL) by their depth information. The formula has been educed to calculate the depth information of a point in virtual scene by the parallax based on a parallel binocular vision model. A bilinear interpolation algorithm has been submitted to deform the segmentation template and take image splicing between three key positions. We also use the positional and directional transformation of binocular virtual camera bound to user avatar to drive the transformation of stereo panorama so as to achieve real-time consistency about perspective relationship and image masking. The experimental result has shown that the algorithm in this paper is effective and feasible.

Although panorama has been intensively researched in recent years and there are many tools on panorama creation, existing methods still can't cope with ghosting effectively and almost all the tools can't create an image with a large vertical field of view. By modifying the sobel operator, we present an improved algorithm to deghost based on dynamic programming. Our new algorithm is simple and robust. This algorithm has been used in our new panorama authoring system, EasyPanorama. This paper describes the architecture, the interactive authoring and publishing process of this system. The system treats panorama as a type of wide angle image, and can vertically mosaic the source images to create an image with a large vertical field of view. With this system, the user first creates a wide angle image, then edits the walkthrough of the panorama if the wide angle image is mosaiced to be a panorama and finally publishes the result to the web.

An effective algorithm for automatic matching between images based on spherical warping model is proposed in this paper. A spherical panoramic image is constructed for a sequence of images taken from a hand-held camera. The focal length of camera is estimated efficiently by using the algorithm of equidistant matching, and images are warped to the surface of sphere whose radius equals to camera focal length. A longitude can be found when image strips located at an equal distance from the image centers moved some angular distance on the spherical surface, thus a pairs of overlapping images can be registered, so image sequences of each swath are stitched to construct panoramic image mosaics, then the panoramic image of different swaths can be stitched to generate the full view spherical panoramic image. The experimental result is satisfactory.

The methods of image registration and fusion are very important basis of cylindrical panorama creating. There are many relevant algorithms been developed, but many of them usually have limitations on their qualities and efficiency. In this paper, an automatic approach for creating cylindrical panorama is introduced. Compared with many commonly used algorithms, this algorithm is simple and effective. In our method, we adopted an FFT-based phase-correlation algorithm to register images, and we also employed a multi-resolution pyramid algorithm to perform image fusion. By preprocessing the input images using such methods as histogram equalization, we further increased the accuracy and robustness of image registration. Our experiments show that the method is simple, efficient and effective.

In this paper, we propose a new method to detecting the moving objects using the orthogonal Guassian-Hermite moments. For the segmentation of moving objects in the moment images, we propose the fuzzy relation method (FRM) and 3D morphological relaxation method (3DMRM). Finally, we analyze the trajectories, speeds and accelerations of moving objects; determining moving direction of moving objects. The experiment results are reported, which show the robustness of our methods.

A texton-based texture synthesis algorithm is presented in this paper. Based on the Markov Random Field (MRF) model, the algorithm takes a block randomly from a given sample texture to form a seed area in the center of the synthesized output texture, then synthesizes the output image pixel by pixel spirally along the edge of the seed area. When sampling a pixel from the sample texture in the synthesis procedure, the algorithm adopts so-called candidate search, global search and central search to preserve the integralities of textons in the synthesized output texture. It was practically improved that the algorithm does better than the existing methods in quality for synthesizing most kinds of textures, especially for synthesizing the complex textures.

This article introduces a reflexion about behavioral specification for interactive and participative agent-based simulation in virtual reality. Within this context, it is necessary to reach a high level of expressiveness in order to enforce interactions between the designer and the behavioral model during the in-line prototyping. This requires to consider the need of semantic very early in the design process. This reflexion leads us to propose a kind of mixed imperative and declarative model which focuses on the link between decision and action, and to the building of a tool capable to simulate virtual environment implying agents based on this model. Intentionality is introduced as the basis of a behavioral model which is given as an example of this approach.

Recent interest in large displays has led to the development of a variety of multi-screen display systems, most of which are comprised of multiple projectors situated for front or rear projection onto a screen to form a large logical display, and each projector is driven by one PC, augmented with high-performance graphics accelerator card. However, most of these systems are immediate-mode based, that is, all geometry data and control information must be sent on the run, and thus the interconnecting network bandwidth between clients and servers has become a fatal bottleneck. In this paper, we describe MSPR, a retained-mode based multi-screen parallel rendering system which offers the programmers with a OpenGL-like API. And the system could be run locally on one PF or parallelly rendered among any number of Computers. The details of data distribution, load balance, interconnecting network architecture, tile mosaic, etc. are hidden from the programmers.

High Level Architecture (HLA) is a new architecture for distributed simulation. Its purpose is to facilitate interoperability among the simulation applications and to promote reuse of simulations and their components. Object Model is important to implement purpose of HLA. OM provides a standard template to describe the abilities of simulations joining federate and the demands of outer systems. This paper introduces the basic content of HLA and describes the components of OM. Based on the authors' comprehend and practice, the paper analyzes the object-oriented characteristic of OM and the ability to support interoperability and reuse of OM. With the primary practice of navy slavage drilling simulation system, the authors give the designing of OM with an example acccording to the designing principle of OM.

HLA (High Level Architecture) is a new architecture of distributed interactive simulation developed from DIS. We put forward a technical scheme of a distributed interactive simulator based on HLA, and bring forward a concept about distributed oriented-object simulator's engine, as well as an in-depth study on its architecture. This provides a new theoretical and practical approach in order to turn simulator's architecture into HLA.

Agent technology is applied into constructing distributed GIS. A distributed GIS-oriented multi-agent system named as Geo-Agents is designed and implemented. Firstly, the classification, structure and features of agent in distributed GIS are analyzed. There are four types of GIS Agent: system management agent, GIS function agent, interface agent and GUServer. Every GIS Agent is a synthetic entity that consists of control subsystem, functional subsystem, communication subsystem, human-computer interface and data resource, and every GIS Agent is determinate, independent, autonomous, interactive and initiative. Secondly, a message mechanism is used to provide communication and coordination between GIS Agents, and a set of Geo-Agents message types are designed according to the properties of GIS and Agent. After that, the architecture and network distributed model of Geo-Agents are proposed. At last, two sample uses of Geo-Agents are explored: agent-based spatial information navigation and spatial decision-support system.

An architecture of distributed virtual reality system is brought forward in this paper. It's based on a C/S system model, and employs a centralized-and-distributed data distribution model. This data distribution model can efficiently realize concurrency control, and easily ensure the data consistency. It also employs a four-layered structure based on Message Queue to accomplish the collaboration management. This structure is platform-independent and very flexible for further extending and upgrading. In this paper, we'll introduce the C/S system model and the centralized-and-distributed data distribution model, and then discuss in detail how the four-layered structure based on Message Queue realizes the collaboration management.

In this paper, the architecture of creative product's design platform Web-based is proposed, which supports multi-users and provides ASP services, and the Petri net model is built in order to realize the controlling of sharing information, cooperative work and solving conflicts in the distributed virtual design. The hierarchical architecture model is based on XML. The cooperative controlling protocol is introduced in detail and the concurrent controlling problems are discussed.

In allusion to complexity of architecture environment and Real-time simulation of architecture acoustics, a parallel radiosity algorithm was developed. The distribution of sound energy in scene is solved with this method. And then the impulse response between sources and receivers at frequency segment, which are calculated with multi-process, are combined into whole frequency response. The numerical experiment shows that parallel arithmetic can improve the acoustic simulating efficiency of complex scene.

HIVE is a middleware platform for scalable distributed simulation development. In this paper, we introduce HIVE and explore how to develop a scalable distributed simulation on HIVE. To improve the scalability, HIVE focuses on system architecture, communication model and interest mechanism. The four characteristics of HIVE are described as: "middleware platform," "scalability," "complete services" and "reusability and interoperability." We explain how HIVE supports a simulation and the architecture of the application on HIVE, and bring forward the essentials developers should pay attention to and the steps to develop a simulation on HIVE. Finally, a simple demo is also given to address the simulation framework in detail.

Currently one of the main research issues in Human Computer Interaction (HCI) is to develop more intuitive, multimodal and natural interfaces. Among them, the interface for triggering simple actions or selecting objects in virtual environments (VEs) is one of the concerned areas. In this paper we describe an acoustic interface which uses finger snap or hand clap sounds as the input command to initiate events for VE applications. We developed a sophisticated algorithm based on the wavelet transform and neural network techniques, which separate the environment noise from the snap and clap sound. The acoustic interface could be integrated with other interfaces like optical tracking systems to provide a more natural, easy-to-use, efficient and boyd-centered multimodal interaction for virtual reality applications.

Virtual audio environment is an essential part in making virtual environments more real. To solve the problems in the traditional methods of contributing virtual audio environment, for an instant, the heavy cost of time and the monotony in presenting audio sources, a fast audio ray tracing method is put forward in this thesis. Then research work is done in the three stages of the whole process, which are modeling and presentation of audio signals, imitation of audio transportation and feeling of sound. That will function as a basal theory in contributing audio environment. The major point of this part is about three courses below. They are band-pass arrangement of audio signals, different processes of sound in different bands, combination of sound serials and the synchronization of sounds as walking in 3D environment.

Eyes or eyeballs extraction from faces is important in facial feature extraction that is crucial in human-computer interaction and other related applications. According to the eyeballs circle symmetry characteristic in face image, original generalized symmetry transform is modified. A robust algorithm proposed in this paper extracts eyeballs from single face images in three steps: (1) using snake and a Gaussian preattentive filter to generate a facial organ mask, (2) using symmetry characteristic to find some candidate points of eyeballs, (3) validating these candidate points by the eye position information. This approach is tested on the ORL database, in which eye feature is not easy to extract for the reason of glasses or closed eyes, with the exact extraction rate 88.5%. It is shown in our experiments that this approach is robust to noise and some interference from glasses.

Freeform object design and simultaneous manufacturing is a novel virtual design and manufacturing method that aims to enable creative and individualized product geometry design and rapid manufacturing of the designed model. The geometry is defined through the process of "virtual sculpting" during which the designer can touch and visualize the designed object in a virtual environment. Natural human-computer interaction is a key issue for this method. This paper first briefly reviewed the principle of the method, including the system configuration, data flow, and fundamental algorithm. Then an input/output device was developed to achieve natural human-computer interaction. Structure of the device and algorithms of calculating the input coordinates and output force were presented. Finally a feedback model was proposed and discussed to apply force feedback during virtual sculpting design.

This paper proposes a simple implementation of audio virtual surround sound effect and a novel scheme for multichannel coding using virtual prediction technique. We used the data of Head Related Transfer Functions (HRTFs) to produce virtual surround sound channels, and mixed them into original stereo channels. The resultant effects were passed the subjective evaluation and implemented real-time on a Motorola DSP. Using the virtual prediction technique, we can remove redundancies between inter-channels in multichannel coding. Therefore, a new coding scheme and method thereof are given. It is helpful to decrease the bit-rates or enhance the quality of multichannel audio coding. The feasibility and result are discussed in the end of this paper.

The application of simulation of integrated navigation system based on the RealSim AC1000 VME system is presented. With its programmable peripheral interface, the information of ship's inertia navigation system (SINS) can be input to the AC1000. At the same time a "mathematic system" is built in it which can simulate the operation of integrated navigation system. With the support of SINS's information, a hardware-in-the-loop simulation of integrated navigation system is designed. The results of simulation demonstrate the effectiveness of mathematical model for integrated navigation system, and the economy of real-time simulation system in scientific research. It plays an active role in the development of system.

Controlling 3D virtual human arm to achieve given tasks is a challenging goal for computer animators. In this paper, a new approach is proposed to plan the arm trajectory in three-dimensional space, which is an extended minimum hand jerk model based on spacetime constraints. Experimental results show that natural arm motion could be obtained by it.

The design and implementation of a wearable computer, which is used in the outdoor AR (Augmented Reality) system in Yuanmingyuan garden, is discussed in this paper. The performance and portability of the wearable computer system are the key factor for the proposed outdoor AR system. The design principles and schemes, which must be considered during prototype development, are presented. A prototype of the proposed wearable outdoor Augmented Reality system for Yuanmingyuan garden is developed, which also shows its application scenario in the reconstruction of other historic remains.

Three key technologies influence the performance of current AR (Augmented Reality) system, namely image grabbing, accurate registration and binocular stereovision. This paper studies a vision-based AR system and its setup, presents an image grabbing solution using an IEEE 1394 interface, discusses the binocular stereovision technology and develops an effective Gauss-Newton iteration algorithm for registration. Experiment results show that the proposed method is computationally efficient and accurate.

A typical Virtual Reality (VR) based ship steering simulation structure, which is helpful to test and modify control algorithms and parameters, is proposed in this paper. The 6-order mathematical model of ship steering is given. This paper focuses on how to develop the 3-D simulation system for ship steering and sea wave, which is essential to interactive visual simulation. A simulation scene including autopilot, rudder, propeller and other marine power plants is presented.

Virtual Reality leads Digital Product Development technology to a more effective and convenient way by presenting the product model in an immersive real 3D environment. Distributed VR even gives the possibility for partners to discuss the design of the product independent of their locations. This paper introduces the ongoing work with a Digital Product Development System with Virtually Cooperating Teams Using Optical Networks -- ProVit, which aims at building up immersive telepresence systems for design review running over high-bandwidth networks. Video and audio streams are integrated in the virtual environment to support teleconference aspects of the distributed design review sessions. A network management system has been developed for the supervision, maintenance and processing of distributed setups, and network security.

This paper describes the application of the methodology of genetic programming to a computer-aided design of the control programs for CNC (computer numerical control) machine tools for thermal metal cutting. The designed set of algorithms and programs is intended for automated design of optimal trajectories of closed paths in a bivariate area given by a technological map of cutting. The results obtained give a reason to believe that application of artificial intelligence technologies in CAD will allow to effectively solve the NP-complicated problems of discrete-continuous structure.

Based on the structure of virtual assembly system, a comprehensive survey and analysis of the recent research in the field are given, which include assembly modeling, constraint recognizing and solving, collision detection, assembly plans and evaluation and so on. The future research trends are presented.

The three-dimension entity models of virtual NC laser cutting machine tool are built through practical measurement. The key technologies and realization methods of machining process simulation for virtual laser cutting are emphasized and discussed. The simulation system of laser cutting process is developed; Finally, the examples of laser cutting simulation are given and the current problems and research directions are pointed out in laser cutting process simulation.

Aiming at the problem that non-programmers cannot find an efficient tool of establishing virtual coal mine in the course of applying virtual reality technology to coal mine fields, an assembly virtual coal mine developing system is introduced. And then, the structure and realization means of the system are discussed. The system has been realized on normal computer and proved to be feasible in practice.

The development cycle of an embedded system should be shortened now. However, in order to perform rapid product development, there are various problems to be solved. Especially, in development of the embedded software which controls embedded machines, as debugging the embedded software cannot be developed until the system (hadware and mechanism) is completed, loss of time in development arises and the progress of the whole product development will be inhibited greatly. In this research, we build a virtual machine in virtual space, and create an interface between an embedded software and virtual machine. It is considered that embedding the software embedded in the real system into a virtual machine, and working the virtual machine.

Significant advances have been made in the field of complex construction process simulation. However, no convenient graphical support tools exist that can depict the construction process in 3D dynamically. In this paper, with the application of Geographic Information System (GIS) and visualization technology, a GIS-based 3D dynamic demonstration system for complex construction process is developed. The three-dimensional vector model, graphic data structure and animation of construction process are given. Based on these, a 3D animation of the whole construction process is carried out and the construction process is presented visually. Finally, this system is applied to a large-scale underground structure group construction. The results show that visualization of simulated construction process has excellent intuition and provides abundant information for engineering decision-making.

The original vehicle license plate images, acquired by black and white camera, are gray level images. In order to facilitate the location of the characters into the license plate, a threshold technique could be applied. However, the images are not uniformly illuminated and have much noisy, it is difficult to find automatically a good threshold that allows the various characters to be isolated from the background. In this paper fuzzy entropy based on both the gray information and Shannon's function, and the fitness function based on the minimizing of the fuzzy entropy in the genetic algorithm was used. The experiment result shows the method effective.

Reality scene is one of the most basic and important technologies in visual system of flight simulators. It includes real terrain, terrain object and physiognomy. Nowadays, it is usually constructed with digital elevation model (DEM) and remote sensing satellite data. In spite of the fast development of computer hardware, it is very difficult to generate large area reality scenes in real-time. Therefore, model simplification, multi-resolution rendering and level of detail (LOD) become the hotspot of recent research. Multi-resolution rendering is the development and extension of the LOD, model simplification is the key in generating a lower resolution model from a complex higher one. Based on the manufacturing practice of some flight simulators, this paper discusses ways of reality scenes' generating and simplification, and dynamic data partition and schedule based on viewpoint.

Traditionally, 3D models, even so called solid ones, can only represent the object's surface information, and the interior is regarded as homogeneous. In most applications, it is necessary to represent the interior structures and attributes of an object, such as materials, density and color, etc. Surface model is incapable of bearing this task. In this case, voxel model is a good choice. Voxelization is the process of converting a geometrically represented 3D object into a three dimensional volume of dataset. In this paper, an algorithm is proposed to voxelize the polygonal meshes ported from current CAD modeling packages into volume datasets based on the easily indexing property of Octree structure. The minimal distance to the feature voxel (or voxels) is taken as criterion to distribute different material compositions to get a new kind of material called FGM (functionally graded material), which is suitable for the interface of RPM (Rapid Prototyping Manufacturing).

Hierarchical levels of details (HLODs) have proven to be an efficient way to visualize complex environments and models even in an out-of-core system. Large objects are partitioned into a spatial hierarchy and on each node a level of detail is generated for efficient view-dependent rendering. To ensure correct matching between adjacent nodes in the hierarchy care has to be taken to prevent cracks along the cuts. This either leads to severe simplification constraints at the cuts and thus to a significantly higher number of triangles or the need for a costly runtime stitching of thse nodes. In this paper we present an out-of-core visualization algorithm that overcomes this problem by filling the cracks generated by the simplification algorithm with appropriately shaded fat borders. Furthermore, several minor yet important improvements of previous approaches are made. This way we come up with a simple nevertheless efficient view-dependent rendering technique which allows for the natural incorporation of state-of-the-art culling, simplification, compression and prefetching techniques.

This paper presents development of a virtual environment that can be applied to the ankle rehabilitation procedure. We developed a virtual football stadium to intrigue a patient, where two degree of freedom (DOF) plate-shaped object is oriented to kick a ball falling from the sky in accordance with the data from the ankle's dorisflexion/plantarflexion and inversion/eversion motion on the moving platform of the K-Platform. This Kickball Game is implemented by Virtual Reality Modeling Language (VRML). To control virtual objects, data from the K-Platform are transmitted through the communication module implemented in C++. Java, Java Native Interface (JNI) and VRML plug-in are combined together so as to interface the communication module with the virtual environment by VRML. This game may be applied to the Active Range of Motion (AROM) exercise procedure that is one of the ankle rehabilitation procedures.

In order to research, perform statistical analysis and broadcast the information of SARS epidemic situation according to the relevant spatial position, this paper proposed a unified global visualization information platform for SARS epidemic situation based on Web-GIS and scientific virtualization technology. To setup the unified global visual information platform, the architecture of Web-GIS based interoperable information system is adopted to enable public report SARS virus information to health cure center visually by using the web visualization technology. A GIS java applet is used to visualize the relationship between spatial graphical data and virus distribution, and other web based graphics figures such as curves, bars, maps and multi-dimensional figures are used to visualize the relationship between SARS virus tendency with time, patient number or locations. The platform is designed to display the SARS information in real time, simulate visually for real epidemic situation and offer an analyzing tools for health department and the policy-making government department to support the decision-making for preventing against the SARS epidemic virus. It could be used to analyze the virus condition through visualized graphics interface, isolate the areas of virus source, and control the virus condition within shortest time. It could be applied to the visualization field of SARS preventing systems for SARS information broadcasting, data management, statistical analysis, and decision supporting.

In this paper we describe the pre-processing works of Virtual Chinese Human (VCH) dataset. And we developed a new hybrid volume render method which uses parallel computer system to implement high resolution visualization of the large dataset of VCH. Some research prospects of VCH dataset are also discussed.

A component-based WebGIS system Geo-Union is introduced, which is built by COM/DCOM technology and can run in Internet/WWW environment. First, the architecture of Geo-Union and the functional partition of Geo-Union component are expatiated. Then, the design and implementation of map visualization objects are described and discussed in details. At last, a sample in Visual Basic environment is given to illustrate the use of Geo-Union components and its map visualization objects.

A simulation system of collaborative forest fire fighting is designed and implemented, several key implementation techniques such as virtual reality, DIS simulation, the modeling of fire and system architecture are discussed in detail. Experimental results show the efficiency of the prototype system.

In this paper, a model for web spatial data visualization based on the oracle spatial database is presented. The paper introduces the basic concept of spatial database and web services, then discusses the four-layer structure of the application on web services, that is: the client, the application server, the web services, and the database server. The paper analyzes the system structure of the data model, the data organization and the expression of spatial graphical features.

Considering the fuzzy characteristics of medical data field and requests of practicability, the paper presents a novel cell projection algorithm based on edge transition region of medical 3D data field. First, 3D data field is pretreated to a unitary and integral field, and the paper extends the method of segmenting 2D image and makes it can be used to extract edge transition region of 3D data field. Then, the edge transition region and the non-edge transition region are projected separately. Last, the realization and experiment results show that the algorithm can improve image quality of edge transition region and guarantee rendering speed effectively.

The General Packet Radio Service is a packet data service for phase 2+ of Global System for Mobile Communications (GSM). It not only defines the packet-switched data service, but also tries to provide quality of service (QOS) guarantees on data flows. Scheduling is an important aspect in supporting of QOS and GPRS. In this paper, two scheduling algorithms, the Modified Earliest Deadline (MED) and Minimum Laxity threshold (MLT), have been elaborated. Both scheduling algorithms allow GPRS to attain high channel utilization, with MTL performing better than MED.

Introduced the application of virtual reality technology in equipment battle damage simulation, given the method of VR implementation, discussed the problems appeared in our research.

Due to the unavailability of appropriate support way that can provide designers with a more realistic and comprehensible feedback from computer-aided design (CAD), the use of CAD technique in planning construction layouts and optimizing schemes for hydroelectric project is limited. Combined with geographic information system (GIS), the method of visual computer-aided design and analysis to project construction basing on 3D dynamic simulation is presented. Then, the dynamic visualization of construction process, 3D digital modeling for the construction layouts, and intuitive analysis on the optimization of construction schemes are achieved. It provides an interactively visualized way for designers to improve their work efficiency and quality.

With the fast development of Monte Carlo global illumination, many new ideas are put forward and needed to be tested whether it is effective. A general and efficient testbed that can provide all kinds of Monte Carlo global illumination algorithms is in great demand. In this paper, we propose a Monte Carlo global illumination testbed for virtual environment -- RenderStorm, which is of highly modular architecture, good expansibility and suitability to synthesize still and animated images. The engine of this testbed is Monte Carlo path tracing technique. Based on Monte Carlo path tracing, it can be easily used for realizing a lot of Monte Carlo global illumination algorithms. A perfectly designed class is the distinct feature of the system. We provide the system with a lot of libraries, which can be used easily.

SVRT (Simulation-oriented Virtual Reality ToolKit), is a high-performance platform, optimized systems are very necessary. We emphasis clipping algorithm in this paper, which provides a flexible and effective approach to clip those objects invisible from current viewpoint. Object-subdivision and none-object-subdivision algorithm are optional for applications developer based on SVRT platform. The later providing an effective, applied and customized algorithm based on multiple bounding types is implemented in SVRT.

In this paper, we will shown an approach to fire simulation in the computer graphics applications. We use the method of volumetric procedural models to simulate fire. The method can satisfy the real-time requests.

For real-time rendering of virtual scenes, this paper presents a new method of adaptive rendering for interacting in Virtual Environment (VE) by use of different visual acuity equations. The VE system may selects one of the equations on the basis of the host's load, and hereby selects a model of level of detail which would be rendered. This method is tested through experiments; experimental results show that this method is effective.

A panoramic image mosaics algorithm based on wavelet decomposition and equidistant matching is proposed in this paper. Firstly, the images are decomposed with wavelet, and then the similarity distance between the corresponding pixels is defined. Secondly, according to the criterion of minimizing the sum of similarity distance, the equidistant matching is used at the every level of the wavelet pyramid to align all the images. Finally, all the aligned images are projected onto a plane or cylinder to construct a panoramic image. To further improve the image mosaics quality, a fade in-out blending approach is also employed in this paper. The algorithm is fairly stable and efficient for the use of the edges values and pyramid structure of wavelet decomposition respectively.

A novel algorithm for automatic 3D facial model reconstruction form a single front-view facial image is presented. First, face and facial features are located. Then feature point depths are estimated from frontal facial measurements through multi-variant linear regression. With these feature points, the generic face model is individualized by volume morphing with a novel Radial Basis Function-based interpolation. Finally, the texture map is generated through cylindrical mapping. Experiments show that the reconstructed model has satisfying visual effects for a broad pose range. Compared with the multi-view based facial model reconstruction, this algorithm is fast, easy to use, fully automatic and has low requirement in hardware, so it has great potential for many practical applications.

Computing technology, especial the Computer Aided Design (CAD)/Computer Aided Manufacturing (CAM), Internet technology and their application, is one of the fast developing industry in the world. Currently, it is applied widely in many fields of textile industry. In this paper, we will focus on the application of information technology in the design and sale of the textile product. The paper will address the following technical problems in detail: virtual presentation and design of home textile product, electronic commerce for home textile product (interactive design and customization).

This paper discusses the application approach of image analogies in simulating for Chinese painting, presents a simple and effective model. Our algorithm includes analyzing, learning, matching and impression generating. Experimental results demonstrate our approach is efficient for simulating of Chinese painting.

In this paper, we present a simple algorithm for texture generation using a set of self-coherent tiles. The tile is called self-coherent if it can be used to tile the plane without discontinuity on the joint. The primary advantage of using a set of tile set for texture generation rather than find-next-at-runtime methods is that once the tiles are found, large expanse of texture can be created very efficiently as needed in real-time. Our tile is created in the process of texture synthesis. Inherence consistency of texture ensures the self-coherence property of synthesized tiles. The method to synthesize self-coherent tile is introduced first. Then, in order to efficiently create as much non-periodic effect as needed, a mechanism is developed to generate a set of such tiles with similar borders but different visual content. Finally the experiment results are shown and the conclusion is made.

Electronic commerce has been the trend of commerce activities. Providing with Virtual Reality interface, electronic commerce has better expressing capacity and interaction means. But most of the applications of virtual reality technology in EC, 3D model is only the appearance description of merchandises. There is almost no information concerned with commerce information and interaction information. This resulted in disjunction of virtual model and commerce information. So we present Electronic Commerce oriented Virtual Merchandise Model (ECVMM), which combined a model with commerce information, interaction information and figure information of virtual merchandise. ECVMM with abundant information provides better support to information obtainment and communication in electronic commerce.

In this paper, Distributed Virtual Reality (DVR) technology applied in Electronical Commerce (EC) is discussed. DVR has the capability of providing a new means for human being to recognize, analyze and resolve the large scale, complex problems, which makes it develop quickly in EC fields. The technology of CSCW (Computer Supported Cooperative Work) and middleware is introduced into the development of EC-DVR system to meet the need of a platform which can provide the necessary cooperation and communication services to avoid developing the basic module repeatedly. Finally, the paper gives a platform structure of EC-DVR system.

A new method is proposed in this paper to resolve the time delay in telepresence system based on virtual reality. This method reduces the time spent by transporting object's visual factors not by transporting the whole image. The telepresence system based on virtual reality is introduced and the key technology is present in the paper.

This paper presents an interactive presentation system for home-used products. In the paper, we analyze the essential functions, implementation methods and technique for the furniture-customized system. The system allows the customer to navigate in the virtual environment freely through Internet and perform some interactive action on the home-used furniture. The manufacturer or businessman can update the original decorative texture library frequently according to the change of the products, design and produce products based on the customer's desire.

The paper proposes a design of multi-agent system, which is used to intelligentize the engineering machinery of cluster. In this multi-agent system, each machine is well intelligentized, and it can not only work automatically, but also cooperate with other machines. We can use software to actualize this system, and also we can use this system to simulate the actual process of the engineering machinery of cluster.

Virtual human is widely used in educational, entertainment, and 3D game software. In this paper, the subsumption architecture, which is popular in robotics, is employed to make a two-level control model. With this model, virtual human can realize collision-free navigation in a dynamic environment. As collision avoidance is realized in the 0-level layer, path planning is completed in the 1-level layer. Finally, an experiment was done in our human animation platform. And the result shows that this control model can guide digital actor navigate collision-freely in the environment with dynamic and static obstacles.

Humans can extend their capabilities to remote environments depending upon the remote teleoperation of mobile robots. The communication between the operator and the robot needs to be fast in order to quickly interact with the environment. However, the data transfer speed will slow down as either the data exchange rate increases or the Internet bandwidth decreases. Undesirable communication time delay invokes system instability. The purpose of this paper is to employ virtual reality technique to minimize the communication delay effect. A novel virtual tracker was developed and served to acquire the real position and orientation of mobile robot. The virtual reality scene is displayed on the remote computer, which needs only to use the data of the robot position and orientation. Instead of transmitting the huge amount of video stream from the robot to the client computer, the time delay can be ignored and system stability achieved.

This paper describes the motion control simulation based on VR for humanoid robot aiming at walking and running. To insure that the motion rhythm of humanoid robot conforms to the motion laws of humans, the body geometrical model based on skeleton and its kinematics models based on the graph of time sequences are presented firstly. Then a control algorithm based on Jacobian matrix is proposed to generate the periodical walking and running. Finally, computer simulation experiments demonstrate the feasibility of the models and the algorithm. The simulation system developed makes us interactively regulate the motion direction and velocity for humanoid robot.

According to the three ways of establishing a measurement simulation system for spatial carrier pose, a practical method of semi-physical simulation is introduced in this paper. This method can explicitly and promptly simulate the pose measurement visually as a carrier moving in space. The process was completed by integrated the powerful graphical function of OpenGL and computer vision technology. Thus it is able to provide the pose measurement of spatial objects on experimental conditions. This paper emphasizes on the implementation of this method and gives some experiment results of the simulation system.

The paper presents our new research area in virtual reality technology combining with electronic by imitation platform for mobile robot. By this platform, path planning will become easier. From rebuilt virtual reality geographic feature by electronic digital map, mobile robot moving in the actual area could be imitated. Mobile robot coordinate could be corrected by virtual reality characteristic point and CCD image.

An optimal earth allocation is of great significance to reduce the project cost and duration in the construction of hydroelectric engineering. Based on previous studies, a new method of optimizing the dynamic system as a static one was presented in this paper. Linear programming was introduced to solve the optimization problem of earth allocation, and then Geographic Information System (GIS) technique was used to visualize the allocation results. With the 3D terrain model and entity model, the whole construction site model could be built. Based on this computer animation was implemented and utilized to intuitively demonstrate the earth allocation process, which is otherwise difficult to be understood by static results described in texts and tables. A case study in an actual hydroelectric engineering construction is presented to illustrate the proposed method and its capability, which also shows its validation and efficiency.

Public perception of flight safety is generally based on the absolute number of accidents and not accident rates. Therefore reduction of the accident rate such that the actual number of accidents decreases must be a primary goal; otherwise the predicted costs and loss of life are not likely to be tolerable by the industry or traveling public. This paper briefs efforts in the virtual flight vision system program to address training pilots avoiding these accidents. The improvement in situational awareness and reduction in pilot workload resulting from the synthetic vision display should allow aircrews to avoid landing short, flying too close to terrain, or blundering onto an active runway. The systems can also aid aircrews in re-planning en route and in the crucial final approach segment, by providing intuitive guidance cues to reduce pilot workload and improve performance.

Virtual reality is an effective way for visualization of science experiments. This paper presents a VR enhanced display system for the experiment of HgCdTe(MCT) single crystal growth by Bridgman method in two steps: In the first step, we construct a numerical simulation model (time dependent) based on the heat transfer in furnace and ampoule. This gives information about the most important parameter during the whole growth process: the temperature distribution in furnace and ampoule. Then, with the obtained temperatures, we have developed a VR environment in the second step to enhance the display of the key parameters information of crystal growth. This helps the researcher to understand the process of crystal growth intuitively.

Based on Simulink tools of Matlab toolbox, the simulation means facing on the frame is applied to transport water system of irrigation works in order to advance efficiency of transport water system. At the same time, differ calculate methods are used to differ style of cell in transport water system and differ sampling time are adopted for differ disperse cell in order to ensure preferably precision and numerical value stability of every tache.

This thesis gives a brief introduction of the background knowledge of producing water gas. Then it proves into the VR theory and the way of realizing it, and introduces how to switch the attribute value into color one. At last, it introduces the modeling and design of complicated imitated system by using the technology of Object-Oriented.

The paper shows an exmaple about the design of virtual DC machines experiment board to satisfy the needs of teachings in DC machines. It's a practical application on education of virtual instruments (VI).

The virtual machining technique is a key issue of Virtual Manufacturing (VM) system, and the simulation of virtual machining process is a focus research field at the present time. This paper addresses the importance of integrating a virtual manufacturing system with the Internet and proposes a web-based, scalable and distributed architecture for developing a platform-independent virtual NC turning system. A Web-based virtual turning system has been developed using Virtual Reality Modeling Language and Java, and describes the structure of the system and the realization of its main functions. The user can easily setups machining conditions, operates the virtual turning machine in a web browser, and evaluates and optimizes the machining process on the Internet.

Virtual Reality technology belongs to advanced computer technology, it has been applied in instruction field and gains obvious effect. At the same time, robot assisted instruction comes true with the continuous development of Robot technology and artificial intelligence technology. This paper introduces a virtual tutor system for robot assisted instruction.

This paper presents the simulated result of three-dimensional liquid velocity profile on sieve trays by using a computational flow dynamics (CFD) model with considerations of volume fraction of gas and liquid and the interfacial forces. The Κ-ε equation is used for the closure of basic equations. For the first time the three-dimensional liquid flow on a distillation column with ten trays under total reflux is visualized. The simulation was carried out with an Origin 200 Server Workstation of SGI Company using Star-CD V3.1 program. Simulation provides the detailed information of the distribution of 3D liquid velocity on the distillation column.

The recent study of agriculture has faced more and more time-consuming problems and digitalizing problems. In order to solve these problems, we raise our proposal of creating a new virtual agriculture system using the technologies of the virtual reality and artificial intelligence. In this paper, we will not only introduce the composition and the control mechanism of this new agriculture system, but also prove its promising future. We will also discuss the wide application fields of this new system.

In this paper, a hall acoustical quality auralizing simulation system is proposed and achieved in the way of the four ways stereo system. With the target of reappearance acoustic field around ears, we adopt an algorithm called sound bunch retracing of image sound sources to obtain the sound pulses response in four directions. On the basis of the formula of location of plane surrounding acoustic image, we replace the sound pressure impulses equivalently. The sound sources image of distinct places is reappeared accurately in the imitation acoustic field. Moreover, in this research work, we also develop computer utility software and reverberation time computation module.

On the basis of general introduction of Virtual Reality (VR) and Geographic Information Systems (GIS) technologies, the application of VR in Tianjin Environmental Geographic Information System is introduced in detail, including hardware and software configuration, system main functions, system designing methods and developing processes.

As the development of computer graphics, scientific visualization and advanced imaging scanner and sensor technology, high quality animation making of volume data set has been a challenging in industries. A simple animation framework by using current volume visualization techniques is proposed in this paper. The framework consists of two pipelines: one is surface based method by using marching cubes algorithm, the other is volume rendering method by using shear-warp method. The volume visualization results can not only be used as key frame sources in the animation making, but also can be directly used as animation when the volume visualization is in stereoscopic mode. The proposed framework can be applied into fields such as medical education, film-making and archaeology.

Based on the structure of equipment and the available amount of maintenance resources, a Petri-net model is established in this paper to describe the equipment virtual maintenance process. The model accurately reflects the relation between the maintaining time and the amount of maintenance resources, and can be usd to count the amount of maintenance resources after the equipment deployment, or control the maintenance process dynamically.

The combination with the virtual reality technology of summary cross-domain communication technology is a follow-on important direction of computer domain now, if one kind of profitable trial that the domain will be in educates with they applications. This article is chiefly studied using the virtual reality technology to construct building the method of virtual campus, and this system makes up of 5 parts, there are prepared lessons room, classroom, laboratory, test room and Dean's Office, and teacher uses this system can found the cross-domain communication of the multi-medium class part, and manages to student, and arranges taking an examination; Students can learn knowledges in the classroom, and can imitate to do the experiment in the laboratory, and putting to the test the room can be in progress from the adaptability examination.

At first, this paper introduces some features about Virtual Reality, which includes concept, practical use, basic character, etc. Then it turns to one of its branch-Virtual Laboratories. Virtual Laboratories developed rapidly in recent years, and it will have great effect on education area. This paper mentions about many advantages compared with traditional laboratories, the supporting technique, practical significance, etc. Later this paper mentions about a practical example in China. "Computer communiction" is a required curriculum in most universities, so "Virtual Communicating Experimental System" is developed to help teaching in TianJin Normal University.

This paper introduces the interaction control technique for creating a multimedia virtual education environment system based on VRML97. The techniques include the using of perception sensors, environment sensors, touch sensor and script programming control. In this paper, the author also discusses the methods in accomplishment of different kind of VRML interactions.

In X-ray digital radiography system based on the image intensifiers, there are many kinds of noise which originate from different imaging elements, such as CCD camera, scintillator photoconvertor, X ray scatter, control circuit, and so on. These kinds of noise have a serious influence on the imaging quality. It maybe influence the result of identifying defects from the image and the spatial resolution of X-ray digital radiography system. In the paper, in order to depress the noise of system, the origin and the characteristic of the noise in X-ray digital radiographic system are studied, and a method and examples are given to depress the noise of X-ray digital radiograph on the principle of M channels' wavelet transforms, multiresolution wavelet analysis and control of coefficient in wavelet. It is shown that the results of noise depression are effective, the spatial resolution of image is improved, the edges and details of image are enhanced. It is also expressed that the method to depress the noise of X-ray digital radiography system by softer is feasible and economical.

The spatial relationship between two single plane angiograms, which is characterized by transformation in the forms of a rotation matrix and a translation vector, is important for 3D reconstruction of coronary arterial tree. The error of transformation directly reduces the precision of 3D reconstruction. In this study, we introduce the methods of 3D reconstruction, analyze the necessity of optimization of transformation, and define transformation by quaternion. Then bifurcations, vessel vectors and branch angles are employed to optimize the transformation, with Levenberg-Marquardt algorithm. The experimental results on the human angiogram data are presented. The Standard Deviation of reconstruction error reduces from 3.8573 mm to 1.0803 mm in image A and from 4.0663 mm to 1.0742 mm in image B respectively on clinical angiogram data. The results of experiments show that the technique put forward in this paper greatly improves the accuracy of 3D reconstruction.

To make the MPS (Marine Power System) design process more economical and easier, a new CAD scheme is brought forward which takes much advantage of VR (Virtual Reality) and AI (Artificial Intelligence) technologies. This CAD system can shorten the period of design and reduce the requirements on designers' experience in large scale. And some key issues like the selection of hardware and software of such a system are discussed.

As the development of long-distance complex water diversion systems in our nation, numerical simulation method is applied widely because of its efficiency, economy and safety. By analysis of the simulation study of water diversion systems, the obvious disadvantages of nowaday simulation method, differential equation oriented simulation, are indicated, and two new simulation methods are introduced in the simulation of water diversion systems, which are the object-oriented simulation and structural drawing oriented simulation. This paper gives the detail process of the structural drawing oriented simulation in water diversion systems. With a simulating instance, it is found that the structural drawing oriented simulation optimizes the simulating model, including improving the structuralization and modularization of the simulation model, advancing the reusability of the simulation program, simplifying the simulation modeling, and making the process of complex water transfer simulation visual and easier.

An algorithm for the detection of the coronary boundaries in single-view angiograms is proposed. The algorithm, the maximal differential curve tracking (MDCT), uses the directional gray value information available in digital angiograms. The search strategy, which is based on differential method, finds a maximal cost edge along a coronary artery. The results show this method is robust and the detected boundary is continuous. It is beneficial to measure the vessel diameter and locate the stenosis.

During the course of image effect evaluation, random and fuzzy factors are both included. Traditional effect evaluation theory adopts classical probability statistical method, which only shows the random factors of remote sensing exploration system, and does not show the influential factors of psycho-physics and psycho-physiology, which are fuzzy factors, hard to be described and quantized exactly. The image effect evaluation method and computer simulation model are set up based on the interaction of mathematical model and probability statistics, and on the Hamming distance. The technology and thinking method can be applied to solve the problem of image effect evaluation in other similar systems.

Accompany with the rapid development of computer hardware, software and network technologies, applying virtual reality technique and 3D imaging technique in E-commerce is affordable and practical. This paper mainly focused on setting up a new E-commerce platform based on above techniques. A new method for speed up modeling and texture mapping is introduced.

Reconstitute the 3-D model of the liver and its internal piping system and simulation of the liver surgical operation can increase the accurate and security of the liver surgical operation, attain a purpose for the biggest limit decrease surgical operation wound, shortening surgical operation time, increasing surgical operation succeeding rate, reducing medical treatment expenses and promoting patient recovering from illness. This text expatiated technology and method that the author constitutes 3-D the model of the liver and its internal piping system and simulation of the liver surgical operation according to the images of CT. The direct volume rendering method establishes 3D the model of the liver. Under the environment of OPENGL adopt method of space point rendering to display liver's internal piping system and simulation of the liver surgical operation. Finally, we adopt the wavelet transform method compressed the medical image data.

The speaker often wants to express his own views boldly in some oral argument cases in the virtual community. However, he hopes that others could not recognize him. For this purpose, we adopted the voice modification technique to meet these requirements. In this paper, we presented a method of rotating the Pseudo Log Area Ration (PLAR) curve to modify the representation of the speech based on the experiments of the relation between PLAR coefficients and personal information. We also deduced a series of equations to testify the accuracy of this method. Using this method we developed a real-time voice modification system based on LP model, and PSOLA method was also added to this system to produce a better effectiveness. Experiments show that our system has good property of real-time and satisfactory auditory effectiveness and it has successfully been implemented in the virtual community.