AbstractâIn this paper we present a WebVRGIS based. Interactive Online 3D Virtual Community which is achieved based on WebGIS technology and web VR ...
2013 International Conference on Virtual Reality and Visualization
WebVRGIS: WebGIS based Interactive Online 3D Virtual Community Zhihan LU∗† , Shafiq ur R´ehman∗† , Ge Chen‡
† Immersive
∗ Shenzhen
Institutes of Advanced Technology, Shenzhen, PRC. Interaction Lab (i2lab), Till¨ampad fysik och elektronik (TFE), Ume˚a University, Sweden. ‡ Ocean University of China, Qingdao, China. Email:(zhihan.lu,shafiq.urrehman)@umu.se client. Otherwise, ESRI’s IMS for ArcView & MapObjects and MapInfo’s MapX Site request the client to pre-installed plugins, or run automatically downloaded Java Applet, to render vector graphics directly in browser. The above two solutions cost too much time. The former should always respond for each real-time analysis and rendering. The latter requires new users to install and download the plug-in, which is not conducive to the promotion of online virtual community.
Abstract—In this paper we present a WebVRGIS based Interactive Online 3D Virtual Community which is achieved based on WebGIS technology and web VR technology. It is MultiDimensional(MD) web geographic information system (WebGIS) based 3D interactive online virtual community which is a virtual real-time 3D communication systems and web systems development platform. It is capable of running on a variety of browsers. In this work, four key issues are studied: (1) Multi-source MD geographical data fusion of the WebGIS, (2) scene combination with 3D avatar, (3) massive data network dispatch, and (4) multiuser avatar real-time interactive. Our system is divided into three modules: data preprocessing, background management and front end user interaction. The core of the front interaction module is packaged in the MD map expression engine 3GWebMapper and the free plug-in network 3D rendering engine WebFlashVR. We have evaluated the robustness of our system on three campus of Ocean University of China(OUC) as a testing base. The results shows high efficiency, easy to use and robustness of our system.
Based on Virtual Reality technology, WebGIS is developing into virtual geographical environment, which has undergone three stages: community, virtual village community and virtual city [3]. Multi-Dimensional(MD) WebGIS is a branch of WebGIS which combines 2D and 3D data, and while runing in the web, then gradually developed into a MD interactive virtual community. In this paper we propose and implement Multi-Dimensional(MD) WebGIS based 3D interactive online virtual community, showing geographic environment by MD geographic data, and the expression of 3D model of the participant avatar, supporting the massive virtual geographic environments, while roaming. There is no need to download any additional plug-ins while using our system.
Keywords—Virtual Reality, Geographic Information System, Virtual Community, Virtual Geographic Environment
I.
I NTRODUCTION
The prevalence of “Virtual Reality” technology allows people to contact with a computer simulation space. Virtual community is an organized, goal-directed method, which follows the innovative mechanisms beyond management. It provides not only forums composed of text information, but also virtual communities which present environment by three-dimensional (3D) scene. However, the Forum, one form of community information, can not match the map with real community, failing to meet the needs of users with different backgrounds at the same time. The 3D scene virtual community, such as ‘Second Life’ and ‘World of Warcraft’, usually requires predownloaded client resources, and high performance hardware, which is almost impossible for mobile users. On the other hand, new products in terms of embedded 3D engine in the web browser, as COM component seems like a good solution. But the various plug-in standards make it difficult to develop an all-purpose one.
II.
Virtual Reality Geographical Information System (VRGIS), a combination of geographic information system and virtual reality technology has become a hot topic [4]. Here users do not only need to obtain the landscape geo-spatial data dynamically but also need to perform some analysis, calculations, managements, transfers based on data, and even communication, collaboration work. With the popularity of network based applications, the VRGIS platform based on the network environment also becomes a trend. The application of VRML, X3D and other online VR technologies have achieved networking of VR systems, because of the mass data, the network bandwidth constraints of transmission, a large number of request and multi-user collaboration controls, the online virtual reality technology still face numerous challenges. To improve the accuracy of modeling, the city planning has an increasingly high demand for the realistic display of VR system, however this will inevitably lead to the growth of the volume of data transmission. Virtual scene from a single building to the city scale is also resulting in the increased amount of data. The increasing number of user increase the server load and in more severe cases the server has to deny the services. These challenges and problems directly lead the on-line VR technology failure to provide high-quality service
WebGIS is an Internet-based distributed GIS, with the help of Internet technology which can effectively overcome the shortcomings of traditional GIS, employ the Internet technologies provide such as data acquisition, spatial analysis and location-based services and other functions [9]. WebGIS products introduced by traditional GIS vendors (such as MapInfo’s ProServer, Intergraph’s GeoMedia Web Map) generate map images by the server operator in real-time , transmit to the 978-0-7695-5150-0/13 $26.00 © 2013 IEEE DOI 10.1109/ICVRV.2013.23
BACKGROUND
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to public base on the current network frame. Currently, few companies are investing mass of money to set up a large amount of data server nodes in order to break through the bottleneck of the network transmission speed. Therefore it is necessary to seek new, more efficient and more economical mechanism to create a WebVRGIS system on Internet. Recently , researchers have developed new concepts and theories for examples of ‘Internet of things’ and ‘Cloud Computing’ and also the fashionable of the multi-touch mobile. Furthermore, Obama administration announced “Data is new oil” and invested 200 million to Big Data research especially in ‘Gamefication’ and Data mining. The idea does not only include understand big the data by visualization techniques, but also broadens the channels for data acquisition with sensor technology which is the key technology of augmented reality.
Fig. 1. Architecture Diagram of 3D Virtual Community based on WEBVRGIS.
Based on Virtual Reality technology, WebGIS is developing into virtual geographical environment, which has undergone three stages: community, virtual village community and virtual city [3]. Multi-Dimensional(MD) WebGIS is a branch of WebGIS which combines 2D and 3D data, and while runing in the web, then gradually developed into a MD interactive virtual community. In this paper we propose and implement Multi-Dimensional(MD) WebGIS based 3D interactive online virtual community, showing geographic environment by MD geographic data, and the expression of 3D model of the participant avatar, supporting the massive virtual geographic environments, while roaming. There is no need to download any additional plug-ins while using our system. Our proposed Multi-Dimensional approach provides a solution to the challenges of big data and WebGIS. Currently electronic map mainly use the following data sets: •
Vector map data from digitized standard map.
•
Satellite aerial data.
•
Raster data containing coordinate information.
Fig. 2.
system and Web systems development platform at the same time, fitted in running on a variety of browsers, achieved based on WEBGIS technology and web VR technology.
Google launched Google Maps in early 2004, with the integration of the global space map data and high-resolution images, but not yet achieved integration with the 3D projection data. The representatives of 3D digital map (2.5D) of China are www.edushi.com platform and www.o.cn platform. Beside Google Maps, all the existing platforms have only a single map display form. The www.o.cn map based on 2.5D has developed a online community, but the virtual environment data is not consistent. Other products do not support multiuser 3D avatar real-time interaction in the scene. In addition, the current popular Webgame, neither supporting the massive data nor MD data, thus it is limited to fixed maps, and the map user avatar’s switch between different maps is nonfluency.
A. System function System function module is divided into three modules. Figure 1 is a structure diagram; where as Figure 2 is a data flow diagram. The proposed system can be divided into following three modules according to functionality. 1) Data Processing: The ETL engine is designed to fuse MD multi-source spatial data and preprocess the data into tiles to support M DDRQ − T ree index structure(see Figure 3). Process the attribute data by the projection transformation for the POI information. A variety of common vector, raster data formats are supported, with leading data into spatial database. 2) Background Editor: User management module manages the user information, role and online status; System management module for system logs, system status, operating environment and system configuration; Data management module for data classification and data editing.
To this end, our proposed Multi-Dimensional(MD) WebGIS based 3D interactive online virtual community is a comprehensive solution to ‘big-data’, WEBGIS as well as provides an intuitive ‘online users Forum’ and virtual tools & products. III.
Multi-Dimensional Data Flow Diagram of WEBVRGIS.
S YSTEM OVERVIEW
Multi-Dimensional WebGIS based 3D interactive online virtual community is a Virtual Real-time 3D communication
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Fig. 3.
polygon. etc(OGC OpenGIS) that derived from point, line and surface. Layer container is achieved. A top container Map Scene Manager to unify the operation of the entire map is designed, and index of layers are constructed, forming an inheritance relationship and level management system like M ap ⇒ Layer ⇒ Geometry. Optional R tree or quad-tree indexing mechanism for spatial data [2], is used to increase the efficiency of spatial data query. We deal with projection transformation from longitude and latitude coordinate to Lambert coordinate, making spherical data be fully manifested in 2D scene. Grid map is a data model based on the ranks of the square tiles. It uses a group of tiles to describe the geographic factor. The value of each tile represents a realistic geographical element. Grid map in the MD WebGIS is actually a 2.5D observation of surface-rich, the Mental-RAY is used to achieve scene rendering by calculating the number of triangles, particle hits of singlepixel and light intensity of the model [11]. Multi-camera rendering image formed the whole map by stitching, and according to different scales cut them into 3D landscape map tiles that meet M DDRQ − T ree indexing algorithm requires in the client, then save them in the server-side. When the client browser zoom in, zoom out and other behaviors, 3D landscape map tiles and the 2D vector map data make M DDRQ − T ree-based optimization of data removed to ensure data transmission efficiency. By Ajax technology [10] when the map is moving, 2.5D region can achieve real-time loading according to the viewpoint.
Multi-Dimensional Data Support Engine Architecture.
3) Front Interactivity: MD WebGIS roaming: scaling, translation, ranging, Hawkeye etc; 3D scene roaming: real-time rendering of target building’s 3D scene; 3D avatar interaction: Web2.0 based chat [5], blog [1], RSS, albums, individual cabins etc.; public information release: announcement, carpooling. The part is packaged as 3GWebMapper MD map engine and WebFlashVR 3D user avatar interaction engine. B. System Architecture The system design goal is to develop B/S architecture for our WebGIS-based MD multi-user interactive virtual community. For the massive range roaming, we consider the integration of the MD data supporting both raster and vector data, not only display the 2D vector, but also 3D landscape map data. Meanwhile, by clicking the point of interest area (POI), real-time 3D interactive roaming is conducted. IV.
ii - Supporting 3D Real-time Rendering: Since the models in virtual city always include millions of triangle polygons, which make the models become much finer and complicated. Higher demands in memory capacity, processing speed, drawing speed and transfer efficiency appear. In order to perform real-time rendering of massive data and considering current PC configuration, an interactive rendering system is proposed for Outof-Core [7]. The internal memory only includes the data which need to be rendered. With the efficient algorithm of data schedule, these data can be updated on real time, the continuity of the data access can be guaranteed to give an excellent presentation depending on the viewer’s perspective. WebVRGIS engine is designed using the multi-thread architecture to coordinate the threading through thread pool based on reference count. Our experimental platform is configured Core Duo CPU, allocated a thread ‘thread1’ for data loading and unloading, a thread queue ‘thread2’ for transmit the network data to the local hard disk cache. Thread pool can coordinate the ‘thread2’ smoothly, at the same time transfer the data in a block form which comes from Http or the P2P virtual network. OpenGL-based rendering process cycle is placed in the main thread. Following the viewpoint moving, the frustum is updated. We also employ several optimization technologies of visualization including texture mapping, automatic level-of-detail [8], occlusion culling, rendering path and frustum culling with spherical quad-tree.
K EY T ECHNOLOGY
Our proposed system implementation contributes to following three key areas of multi-user interactive virtual community research and development. A. The integration model of WebGIS and WebVR The VR and GIS integration model is the core of the 3D GIS theory, and it is also a demand for VR technology, in the field of the desktop platform, it already had successful cases [6]. But in the Web browser there is not an appropriate solution. In the design process of this virtual community, we mainly focused on Web-based data sharing and integration of VR and GIS function. i - Seamless integration of multi-dimensional data based on free plug-in browser: Vector data is a kind of data models or structures, which based on rectangular coordinate system, it picture the geographical elements with point, line and surface. Every geographical element is denoted by a set of ordered (x, y) coordinates and integrated with its corresponding property. We designed Geometry model strictly following the OGC OpenGIS Simple Features data specification. The basic geometric shapes are point, line and surface, and multipoint, multi-line, multi-polygon, curve, straight line, ring,
iii - Seamless integration of 3D characters avatar & Map:
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ii - Asynchronous access mechanism: As a result, the engine could interact and transmit mutual data with database at server-side asynchronously and directly after responding to user actions based on Ajax. The request response mechanism makes up the shortcomings of static connection, eliminates the need to download redundant data, and realizes “on-demand access to data”, resulting in improving process speed, minimizing the server burden caused by redundant request and response. Basic data, such as roads, administrative boundaries, cities, lakes, changes seldom, is preprocessed to M DDRQ − T ree main-tree data set, while other instable data will be processed to sub-tree data set of M DDRQ − T ree dynamically.
The 3D characters avatar in traditional webgame or 3D virtual community is showed by 2D or demanding user to download the extra browser plug-in. That does not coordinate the effectiveness and efficiency. This system realizes the WebFlashVR, 3d avatar animation engine. It analyses the key animation model DAE using means of Actionscript3.0. Flash 3D characters animation is embedded in MD WebGIS scene, and rendered as a specific POI node. Using 3D characters avatar to show the user figure can actually simulate human behavior and interaction [12]. Using the WebFlashVR 3D characters avatar, there is no need to download extra plug-in for 3D characters. B. Massive Data Support Mass data and network-limited bandwidth mainly affect the MD data dissemination in virtual community. Thus this issue is primary for the whole system.
C. The GIS application service on virtual community Traffic route query includes: Bus route inquiry, Driving self-contained navigation, carpool information promulgation. The routes and bus site information are stored in database, which can be displayed on the map for inquiry. Based on ‘dijkstra’ algorithm, driving self-contained navigation calculates the optimal path which will display on the map. These functions can be combined with GPS devices, measuring user’s current location, and make it as the starting point of an inquired route. Share-car function acts as intermediary that providing resources information to the users who want to share their cars and the users without car.
i - M DDRQ − T ree Index Structure: M DDRQ − T ree is a deformation of the regular division quad-tree index of the region based on pyramid in network environment, which supports online multi-source, MD data fusion and multi-scale representation. With the pyramid structure of traditional rule-based segmentation of the region quad-tree index in comparison, M DDRQ − T ree added a MD overlapping layer to express MD data. First of all, server-side renders vector data, and spreads the rendered images in real-time to front-side browser to display. In this process, the display efficiency of map depends on the amount of the vector data. In M DDRQ − T ree, Level0 divided the map into m ∗ n regions, each region is split into four sub-trees, and the layer of sub-trees is Level1, the number of rows and columns in map of Level n are as follows: Number of rows: m × 2Leveln , Leveln0. Number of columns: n × 2Leveln , Leveln0. Assuming that the extreme values of the map scope are XM in , XM ax , YM in , YM ax , abscissa difference Δx, and vertical difference Δy; the method to calculate the tile position(i, j) by the geographical coordinates(x, y) is following: i = (Ymax − y)/Δy × n × 2leveln (1) j=
(x − Xmax )/Δx × m × 2levelm
V.
IMPLEMENTATION OF VIRTUAL COMMUNITY SOFTWARE
The system is developed on the VS 2005 (C#) Asp.net2.0 environment. The attribute data and spatial data are stored in SQL Server 2005 database. JavaScript is used to browser construction and Ajax is used to transmit data between browser and server. The system takes the urban areas of QingDao and three campuses of OUC as test examples. Vector data adopts the shape format. The scope covers the area of 1,000 square kilometers of Qingdao city, the scale of the data is 1: 10000. 3D map of community landscape is three campuses of OUC and the total area is about 3000 acres. The 3Ds Max is used for modeling and rendering the map of the community landscape. The map of community landscape is heightened by the parameter script of the platform, after which it is cut into a main-tree tile of the M DDRQ − T ree by the data process module. The three campuses are treated as sub-tree interest set of M DDRQ − T ree. All the 3D models are displayed online by the WebFlashVR engine.
(2)
During zooming in, zooming out and movement M DDRQ−T ree data, by the data coordinates of the new map moved into the scene, we can calculate the location of the required data tiles. We just need to download the new tiles entering into the visual region to fill the missing region. In order to enrich geographic information in map, we insert 3D landscape map data into the 2D vector map using the main-tree index of M DDRQ − T ree structure, as an overlapping sub-tree layer. Overlapping layer structure changes following the move of the main center coordinates of the map, to indicate the 3D area in the map. As shown in Figure IV-A, when the map is moving, the tiles of M DDRQ − T ree overlapping sub-tree are dynamically culled and loaded.
The test server is the HP W1907. The configurations: CPU: Pentium(R) Dual-Core E5300/2.6GHz, Memory: 2GB, Windows Server 2003, IIS6.0, SQL Server2005. The NO.1 client is as the same as server. The NO.2 Client is equipped by DELL M90, the configurations: CPU: Genuine T2400/1.83GHz, Memory: 2GB; Windows XP Professional (SP2), IE 7.0. The Conclusion of the test(see Table I): In the case of 100 concurrent user’s presence. The average number of concurrent requests per second is 1179.86. The average response time of a single request is 0.088 seconds. The number of concurrent requests per second is more than 1000 and a single request of
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Fig. 4.
Fig. 5.
Fig. 6.
Tiles of M DDRQ − T ree overlapping sub-tree are culled dynamically.
System operation interface - First GUI View. Fig. 7.
System operation interface - third GUI View.
Fig. 8.
System operation interface - forth GUI View.
System operation interface - Second GUI View
the average response time is less than 30 seconds. Figure 5,6,7 and Figure 8 are the system operation interface. VI.
CONCLUSION AND OUTLOOK
interactive online community, which is a technology of MD WebGIS. The M DDRQ − T ree index structure is designed to display the massive data online in real-time. The interactive function is available between 3D scene and the avatar of multi-user. The system provides a new idea about design and implementation to the Internet virtual community.
In this paper we present an intuitive WebGIS based 3D interactive online virtual community and MD geographic data integration platform which includes the integration of scene and 3D avatar; massive data network scheduling and real-time interaction among multi-user. All of these contribute the 3D
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R EFERENCES
TABLE I.
D ETECTION ABOUT THE NUMBER OF SERVER CONCURRENT REQUESTS PER SECOND AND THE AVERAGE RESPONSE TIME OF A SINGLE REQUEST Test items
[1] Alvin Chin and Mark Chignell. Identifying communities in blogs: roles for social network analysis and survey instruments. Int. J. Web Based Communities, 3(3):345–363, 2007. [2] David Ebdon. SPANS a quadtree-based GIS. Comput. Geosci., 18(4):471–475, 1992. [3] Jianhua Gong, Wenhang Li, Yabin Li, and Mingxiang Huang. Networked Collaborative Virtual Geographic Environments: Design and Implementation. Virtual Geographic Environments. Beijing: High Education Press, 2009. [4] Bo Huang, Bin Jiang, and Hui Li. An integration of GIS, virtual reality and the internet for visualization, analysis and exploration of spatial data. Int. J. Geo. Sc., 15(5), 2001. [5] Isa Jahnke and Michael Koch. Web 2.0 goes academia: does web 2.0 make a difference? Int. J. Web Based Communities, 5(4):484–500, 2009. [6] Chunyong Ma, Ge Chen, Yong Han, Yongyang Qi, and Yong Chen. An integrated VRGIS navigation platform for city-region simulation. Comput. Animat. Virtual Worlds, 2010. [7] Ahn Minsu, Igor Guskov, and Seungyong Lee. Out-of-Core Remeshing of Large Polygonal meshes. IEEE Trans. Visual. and Comp. G., 12(5):1221–1228, 2006. [8] Jingliang Peng and etc. Geometry-guided progressive lossless 3D mesh coding with octree (OT) decomposition. ACM Trans. Graph., 24(3):609–616, 2005. [9] Zhong-Ren Peng and Ming-Hsiang Tsou. Internet GIS: Distributed Geographic Information Services for the Internet and Wireless Network. New York John Wiley and Sons, 2003. [10] Ahmet Sayar, Marlon Pierce, and Geoffrey Fox. Integrating AJAX approach into GIS visualization web services. In Proceedings of the Advanced Int’l Conference on Telecommunications and Int’l Conf. Internet and Web Applications and Services, 2006. [11] Narushige Shiode. 3d urban models: Recent developments in the digital modelling of urban environments in three-dimensions. GeoJournal, 52(3):263–269, 2000. [12] Vinoba Vinayagamoorthy, Anthony Steed, and Mel Slater. The impact of a character posture model on the communication of affect in an immersive virtual environment. IEEE Trans. Visual. and Comp. Graphics, 14(5):965–982, 2008.
users number (100 users)
Transaction number (a)
1903
The average transaction response (seconds) The average number of (a) concurrent requests per second (a)
16.334 1179.86
Single request the average response time (seconds)
0.088
Passing rate of affairs
100%
The future work will focus on the augmented reality extended application of WebVRGIS engine, the way to reconstruct virtual city automatically, and more intelligent process with considerable urban image search algorithm. At the same time, we have plans to play full potential of P2P architecture, combined with the advantage of the cloud computing, provide the cooperating VR/AR roaming function and GIS analysis function based on the multi-users for the engine, using the WPS (OGC Web Processing Service) to encapsulate the functions and releasing it to the multi-users. ACKNOWLEDGMENTS The authors are thankful to Chinese Academy of Sciences Fellowship for Young Foreign Scientists (2012Y1GA0002), National Natural Science Fund of China (61070147), Ministry of culture of the PRC’s S&T innovation fund under grant (162012), and Shenzhen Scientific & Research Development Fund (JC201105190951A).
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