Research And Implementation On The Algorithm Of LOD Model Simplification

At present, with the rapid development of computer technique and3D visualization,model data, founded in various fields like Geographic Information System, ComputerGraphics, Virtual reality, Biomedicine, Television Animation and so on, becomes more andmore giant and complicated. Triangular mesh, on the surface of the model, is usuallycomposed of millions of, tens of millions of or even hundreds of millions of triangular patcheswhich has great influence on the storage capability and transmission efficiency of computerwhile building a model. As a result, people put forward many kinds of techniques andalgorithms for model simplification while they use the computer with faster processing speedand higher performance. Nowadays, the most commonly used model simplification techniquebelongs to LOD (Level-of-Detail) model techniques. LOD model means that users call all theDetail models according to visual importance of the model in scene. When the viewpoint isvery close to an object, they use the sophisticated model to draw; conversely, when the modelis far from the viewpoint, they use rough model to signify.The present thesis first introduces the related knowledge of LOD model simplificationtechnology, including the research purpose and significance, and several simplifiedalgorithms are classified, further discusses several typical mesh simplification algorithms. Atthe same time, the author introduces several key technologies of model simplification, likesimplification of the error metric standards, the choice of LOD model scale and so on. Basedon this, the thesis mainly focuses on the simplified methods of triangle mesh model, givingthe improved algorithm of mesh simplification based on triangle collapse. This kind ofalgorithm takes triangle collapse as the basic simplified operation, introducing the long andnarrow degree of triangle, the local region area, triangle circum and sharpness of triangle inthe simplification process as the constraint factors of triangle collapse. Then establish a newError matrix and calculate the collapsing cost for each triangle according to this Error matrix.By constructing a simplified sequence of collapsing cost from small to large, it can beconcluded that the triangle with smaller collapsing cost has preference to be simplified.Aiming at the defects existing in the mesh simplification algorithm, like the uniform of oversimplified local region, the disappearance of Sharp features, the poor maintenance of topology structure of the model and so on, the thesis presents an improved mesh simplificationalgorithm of triangle collapse. On the basis of maintaining the original topology structure, thisalgorithm keeps its detailed characteristics.In the environment of Windows XP, the algorithm of this thesis is implemented throughthe use of graphical interfaces of Visual C++and OpenGL. The experimental results showthat through the comparison with the other two kinds of algorithms, this improved meshsimplification algorithm of triangle collapse is better to keep the topology structure andgeometry characteristics of the original model, and the details and visual characteristics of theoriginal model are also well kept. At the same time, the applicability of this improvedalgorithm is common.