Investigation On The Key Technology Of Virtual Environment For Distributed Simulation System

As an important part of virtual reality system, virtual environment is a focus in virtualreality field. Virtual reality integrates into distributed simulation, and the complex virtualenvironment rendering becomes the key point. This dissertation concentrates on the keytheory and technology of virtual environment for distributed simulation system.This dissertation researches the accelerate of complex rendering, multi-resolutionLevel-of-Details modeling, distributed simulation Run-Time Infrastructure, rendering onGPUs, framework for developing and integration, etc. Build a framework of VR based onthe research of key technology of virtual environment rendering. The virtual environmenttheory and algorithm are applied to the application of complex electromagnetic virtualenvironment and the power system simulation. Generally, the main research points in thispaper are as follows:This dissertation introduces the acceleration of rendering for large scale scene. Basedon the space and motion relation, the scene is constructed into a hierarchical tree. A fastvisibility culling method is proposed to accelerate rendering, according to static visibilityculling and dynamic culling correction. According to the research of edge-collapsesimplification of complex model, a new algorithm of LOD models generation is proposedwhich is concern not only geometry properties but also features. To handle the dynamicenvironments in VR, an algorithm based on the extension of resolution is improved usinggrads in the terrain's data to generate progressive meshes.To ease the complexity of virtual environment for distributed simulation and to meetthe requirements of system development, some new technologies such as rendering, GPUs,distribute simulation and design patterns are concerned. A virtual environmentdevelopment framework is designed, using OpenSceneGraph as a rendering engine andCERTI as a HLA component, to archive the flexibility and expansibility. Based on thisframework, the technology of time-space consistent in distributed system is studied, and amethod to satisfied time-space consistent is proposed.In complex electromagnetic virtual environment, GPU is used as a fast simulation tool.A new algorithm for estimation of radar shadow affected by 3D terrain is proposed basedon parabolic equation theory and collision detection method. The shadow zone of radar canbe simulated is real-time. In the situation of radar netting, a voxelization method isproposed to calculatingthe guarding zone and detecting zone. A high resolution GPU clipping method based on quad-tree is used to voxelize the surface. Ray intersectionmethod is adapted to filling the inner space. A fast intersection algorithm is used tosimulate radar netting, based on the voxelization result. The algorithm for radar nettingsimulation is fast, which could provide scientific visualization and decision supporting. Anew Graphical Electromagnetic Computing (GRECO) method for RCS of complex objectsis proposed based on ray-tracing and Physical Optics(PO) theory under multi-scattering.All these algorithms are realized on GPUs to use the ability of graphic hardware.In emergency simulation of power system, a prototype system has been built based onHLA to achieved interoperability and consistency. This system using some key technologysuch as interoperability based on CIM, communication based on HLA/RTI component andthe equivalence simulation of peer power systems. This system is suited for large scaleemergency power simulation. In virtual environment of substation simulator, thearchitecture of transformer substation's virtual environment is studied. A method oforganizing the virtual space and objects' models into a hierarchy tree according to theirelectric relationship was applied. Given an accelerated algorithm of collision detection,which is context-sensitive. Particle system is used to simulate the effects of dielectricbreakdown, rain and snow falling. This immersive virtual environment is successfullyrealized for substation training simulator.