Three dimensional highway real-time visual system design and application

Transcription

1 Key Engineering Materials Online: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland Three dimensional highway real-time visual system design and application Haifeng Li 1, Xuejun Xu 2, Xinsha Fu 2 1 School of Civil and Architectural Engineering, Central South University, Changsha, China 2 College of Civil Engineering and Transportation, SCUT, Guangzhou, china lehaifeng@gmail.com Keywords: Highway, three dimensional, real-time, visual, simulation. Abstract. With the fast development of the freeway construction in China and the increasing demand of the improvement of the landscape and safety in the highway system, the traditional method of the highway alignment design cannot meet the need mentioned above. A Three dimensional highway real-time visual system (3DHVS) is developed as a basic platform for the highway visual and physics simulate, which had many merit in the highway alignment, landscape and safety design by the means of fly-through, interactive and physics simulation with the virtual scene. By analyzing the disadvantage of the widely used design method, a performance and expansible architecture of 3DHVS is presented. Finally, we show the application of the system. Introduction With the fast development of construction of the road in China, the concept of safety, environmental protection, comfort and harmony is served as the target of sustainable development of highway design and construction. In fact, the traditional highway design cannot meet the increasing requirements in the landscape, alignment and safety. As a result, as an improved method, three-dimension technology is more and more extensively applied as a means to aid design, and display and evaluate the design results. The traditional highway design method is to use 2D (mainly including horizontal, vertical and cross section) design to emulate three-dimension information, which has reasonably simplified the highway geometry design in the past years [6]. However, at the process of simplification, the three-dimension information cannot be presented resulting in unavailability of information on harmony between highway and environment and inability to make an object evaluation on the relationship between the alignment and the safety. In this case, it is believed that its disadvantage exists in evaluating the highway landscape, alignment and safety, which will eventually make an unfavorable effect on the future highway construction on environment, economy and society [6]. In China, lots of studies have been made in the field of highway three dimensional simulation [1][2][15]. The work flow used in these studies is: First, the highway meshes are created based on the design data using road CAD software generally under the platform of AutoCAD; second, other models are generated including the terrain, the plants, the accessories around the highway; third, all of these models are integrated under the 3D modeling software such as 3dMax, Maya, and Blender; finally, after a long time of non-real-time rendering, the video files can be produced for the purpose of the landscape and alignment evaluation. Such kind of method is called static 3D visual which can render the highway and scene in a realistic way but still has some limitations as following: 1. Limited angle of view. Dynamic, arbitrary and interactive fly-through is impossible since the scanning can only be achieved along pre-scheduled track. 2. Inability to expand and limited support functions. All the functions and paths should be scheduled beforehand. Moreover, expanding more functions based on the original one not only requires re-starting all over again but also is time-consuming. 3. Shortage of the interactive function. Consequently, it is impossible to get any additional information except pre-set information. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (# , Pennsylvania State University, University Park, USA-19/09/16,06:49:10)

2 64 Materials, Mechatronics and Automation 4. Low efficiency in aiding design. Making such kind of animation often costs a lot of time. What s more, any modification on design will lead to re-starting. In general, a real-time scene render only takes a few minutes while 3Dmax or something else takes a few days or even more time. With the development of computer and Cg technology, it is feasible to build a real-time system which allows for freely fly-through, dynamic interactive query about any information the users want in order to improve design quality. The three-dimensional highway real-time system (3DHVS) is to integrate the highway model made up of by horizontal, vertical and cross section information, and the models of the terrain, the vegetation and the accessories around the highway to form a virtual environment, enabling designers to figure out the defects in the design. So the research and development of 3DHVS play an active role in improving the design level and evaluation quality in the highway construction [5]. This paper focuses on analysis of the system architecture and the functions as well as system modeling, the hierarchy and inherited relationship between classes by the Object-Oriented method. So this paper doesn t involve in the system realization and arithmetic. This article is organized as following: the second section describes the architecture of 3DHVS, the third section describes the application of 3DHVS, the forth section makes a conclusion. The architecture of 3DHVS The target of the system Based on Digital Terrain Model[4][8-10], and Road CAD[6,7], 3DHVS allows for fly-through and query about ground attributes and attributes of road design, offering dynamic design results of object and 3D with a view to appraising the quality of the design results and harmony effect between road and environment. This system can be integrated with digital photogrammetry on the data level to render virtual after-construction landscape. Simulated driving in this environment allows for object experience of alignment quality, landscape along the road and harmony between the previous ones. With geologic database set up, with the aid of 3DHVS, it is convenient to make geological alignment selection. 3DHVS, with the help of 3D data management sub-system based on the 3D object data structures in it, can accomplish management of various data of complex structure, superior to digital terrain model system which can only handle terrain but cannot display the objects such as bridge, road and vegetation. As a result, it can specifically display the structure attributes of roads, bridges and accessories. In addition, on the ground of physical simulation system, 3DHVS can exactly reproduce road accidents and appraise the quality of alignment design in terms of safety. System construction design A well designed architecture was the basic of a flexible, extensible and maintainability system. According to the principle of structured frame, the system can be designed as the following hierarchies: The system support layer includes hardware, operating system (regarded as a virtual machine), and graphics application interface. The former is to take charge of the hardware operation, processes management, memory management and I/O attempter; the latter is to take charge of calling instruction of the GPUs via OpenGL or DirectX 3D. What s more, with the modern GPU development and the help of OpenAL or CUDA, we can explore the parallel ability of GPU to get high rendering performance and photographical affection. The Graphic and physics engine layer is core module to render objects in highway scene and to simulate the behavior of dynamic objects such as vehicles. The graphic engine layer can be seen as an engine which input graphic elements such as geometries, textures output images display at screen. The most important parts of it is that the highway scene management which partition the scene into lots of sub parts to make high performance, such as BSP tree, octree; the material management which manage the material of the deferent objects and deferent level according to the ability of the hardware and the distance to the camera; the rendering management which manage the render the objects pass to the hardware using fixed pipeline or programmable pipeline.

3 Key Engineering Materials Vols The physics engine is the core module to simulate the objects physics behavior, such as weight, velocity, rigidity and so on. It also takes charge of modeling of dynamo behavior of automobile and automobile s collision. Through this model, with reference to the data resulting from quantifying the performance and track of the automobile, checking is made on highway design parameter, providing the basis of appraisal of coherence between driving safety and road alignment. The highway modeling layer is the core module to offer the geometry and material information of highway objects such as terrain, road, bridge, and tunnel. This is a highly automatic process according to design data. Highway 3D model is created on data of horizontal, vertical and cross section. Highway network can be well described by means of departing-integration. The highway is abstracted as the collection of the segments means a section of the highway and the nodes means is the connection of the segment such as intersection, the bridge. The segments and nodes are sewn together by fitting their cross sections together like the teeth of two gears. The highway network can be well described on this way. And the constrained Delaunay triangulating is used to implement the seamless join the highway and terrain together [4][12][13]. The system mainly adopts triangle irregular network (TIN)[10][14]. Empirical evidence shows that simulating terrain surface through triangles as the basic primitive can satisfy project s practical requirements. In this case, the system includes Delaunay triangulating from discrete terrain points and constrained Delaunay triangulating (CDT) with data of highway boundary line as constrained region. Module of landscape modeling includes modeling of highway accessories, those objects of continuity or regular distribution with simple structure such as vegetation, anti-crash handrail, wave-shaped handrail and street lamp and the modeling of other objects. Other objects such as building and bridge are relatively complex and in random distribution. Consequently, the model is created in 3D model software in form of files read by the users by means of interaction and imported into the scene. Figure 1. The system architecture and process flow of the system. The application layer is the core module for data obtaining, transforming and handling. It consists of data transform between all kinds of the file format, the modeling in 3D for the road, the terrain, the bridge and so on, the evaluate system for the relationship between the highway alignment and the safety, and the physical engine for the drive emulator. The system architecture and process flow of the system shows as following:

4 66 Materials, Mechatronics and Automation Application The 3DHVS was tested with the terrain and highway design data from Guang-Wu expressway from Shanwei in Guangdong province to Qingshui in Yunnan province. Triangle irregular network digital terrain model is showed as figure 2, the seamless join between highway modeling and the terrain model is showed as figure 3, and the finally result of the landscape rendering is showed as figure 4 and figure 5. Figure 2. Triangle irregular network digital terrain model[7] Figure 3. The highway modelling[7] Figure 4. The highway modelling and clapboard modeling

5 Key Engineering Materials Vols Figure 5. The highway modelling and clapboard modeling Conclusion In this paper we have discuss the architecture and process flow of 3DHVS. It shows good performance and vision effects in applications. But there still lots of thing to improve, which including building distributed application, add GPU based LOD arithmetic and parallel multi thread to improve performance. Acknowledgement This paper supported by Guangdong Provincial Highway Administration Bureau Research Project References [1] Cao Zhenyu, Qi Hua, D Geometrical Modeling For Highway. Railway Investigation and Surveying, 29 p [2] Chen Dongsheng, Application of 3D-Animation to Highway Landscape Design. Journal of Central South Highway Engineering, 29 p [3] David H. Eberly, D Game Engine Design: A Practical Approach to Real-Time Computer Graphics. Morgan kaufmann Publishers, p (2001) [4] D. T. Lee and B. J. Schachter, Two Algorithms for Constructing a Delaunay Triangulation. International Journal of Computer and Information Sciences, 9 p [5] Erich Gamma Design Patterns: Elements of Reusable Object Oriented software. Addison Wesley, p. 1-19(2000) [6] Fu Xinsha, Gong Dejun, Development of Highway Survey and Design Technology in China. China Journal of Highway and Transport,11 p [7] Fu, Xinsha, Haifeng Li, Juan Zhu, Ejun Xu. Architecture analysis of a three-dimensional highway real-time system. 25th Annual Southern African Transport Conference, SATC : Will Transport Infrastructure and Systems be Ready. Pretoria, South Africa,

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