Research On Real-Time Algorithm Of Viewing Scene In Distributed Train Simulation System

Distributed architecture is a direction of train simulation system. Visual system is an important component of a distributed train simulation system, it is a key factor to evaluate whether the system is advance or not. CGI (Computer generated image) technology is used to generate scene in advanced train simulation systems. In this dissertation, the author has done a deep going research on some key technologies used in distributed train simulation system and it's visual system. The main contributions of the dissertation are:1. DIS (Distributed Interactive Simulation) technology is ap- plied to build a distributed train simulation system. In this system, a DR (Death Reckoning) algorithm adapted to train simulation is used to avoid frequent data exchange between nodes.2. A SGI graphics workstation based visual system and a PCs based distributed visual system are implemented. And characters of these two visual systems are compared in the dissertation. In PCs based distributed visual system, PCs with AGP (Accelerated Graphics Port) cards act as scene generation nodes. IP multi-cast technology is applied to implement the communications between nodes. Three channels scenes can be rendered synchronously by the PCs based system. And the system can satisfy the real-time demand of train simulation system.3. An OpenGL based high-level graphics API is implemented. Trees and linear lists are main data structures of the API. In this API, OO (Object Oriented) high-level functions such as scene management and rendering are supplied. The API constructs a elementary software platform of train visual simulation.4. Real-time rendering of terrain surface model is discussed and a view-dependent real-time continuous LOD (Level of Detail) model generation and rendering algorithm for large scale terrain is presented in the dissertation. The algorithm is a regular network based refinement algorithm and quad-tree is the main data structure. Hierarchical bounding boxes are used to implement fast view culling. Screen space errors of blocks and triangles are used to determine whether these blocks and triangles to be refined or not. Force split can be done in the process of refinement. The results show that the algorithm is efficient in space and calculation.The algorithm can be applied in train visual simulation.5. Simulation of some nature phenomena is implemented in train visual system. A real-time particle system is applied to simulate snow and rain. In the particle system, simulation model of snow and rain is simplified to satisfy the real-time demand of visual simulation. And simulation of sky, cloud and daytime is implemented.