Research On Key Technology Of Interactive Visual Simulation For Highway

With the rapid development of the national economy and transport services, highway construction in China has entered a new period of development, and is increasing in a large quantity. In order to improve the safety of highway traffic, discover and correct the potential safety problems in the project earlier so that a highway with higher security can be designed and modified. The evaluation of highway safety based on vehicle driving simulator has become an important research topic. The large-scale three-dimensional visual simulation of highway has become a key in the experiment of simulation and evaluation of traffic safety. The visual simulation of the highway can not only be used as the basis for evaluation of highway safety, but also be used as a demo to display the effect of the project during the bidding process or after the completion, which has important research significance.This thesis first describes the overall division scheme of large-scale highway scene based on the real terrain and road data, and then introduces the terrain and road matching algorithm and the fast generation method of large-scale terrain based on the CAD data. Furthermore, a framework for the rapid construction of a highway visual simulation system has been studied. And it's applied to the LiuWu highway visual simulation system based on the real design data.The main contents of the study are as the following aspects.(1) The overall division scheme of large-scale highway scene is studied. Most of the highways are very long, which determines the large-scale characteristic of highway scene. In order to organize the scene effectively, reduce the consumption of computer memory and improve the rendering efficiency, the entire highway scene must be divided into parts. This thesis has proposed the scene dividing scheme based on the highway's linear trend due to the linear and narrow features of highway.(2) The terrain generation technology based on the real terrain data is researched. Terrain simulation is the most important part in the highway visual simulation. The original datas are necessary for generating the terrain in order to reproduce the real topography surrounding highway. The thesis has analyzed the DXF file format and discussed the discrete points extraction algorithm based on the the original terrain data from CAD. Then we use the surfit software to interpolate the discrete points and generate grid terrain model. Additionally, the technology for rendering and multiple texture mapping of the grid terrain model has been studied. And the multi-block connection problem between the terrain is solved by using a terrain block fusion algorithm.(3) The matching problem of terrain and road is studied. In the process of highway visual simulation, road and terrain model are created in different ways. Sometimes the established terrain model doesn't match the road model since the terrain data is obtained through aerial photography before construction of the highway, and will be modified during the process of road construction. Therefore, the matching of the terrain and road is necessary. The thesis introduces a matching algorithm for the terrain and road based on grid terrain model.(4) The simulation framework for the building of highway scene is researched. This thesis discusses a data-driven highway simulation framework to build a highway visual simulation system quickly. A dynamic scheduling strategy was used to solve the problem of real time walkthrough in a large scale highway scene. And a automatic walkthrough program is proposed based on road alignment. The jitter problem during the process of automatic walkthrough has been solved by using spherical linear interpolation. The LiuWu highway visual simulation system based on the original design data has been implemented.