Research On The Technology Of 3D Mesh Model Simplification

Along with the development of modeling techniques and data acquisition devices, there are more and more large scale 3D models. These models can accommodate the need for details, but their data are so large that it is very difficult to store, transmit and render, the large data overwhelms the rendering performance of current graphics systems. In many cases, we do not need such highly detailed models, so it is necessary to simplify these models. Model simplification is to take a detailed model as input and generate a simple approximation that looks similar to the original one and satisfies the demanded precision. Model simplification can reduce the model's data, and accelerate the process. The technique of model simplification has been widely used in many fields.The dissertation is focused on the research of popular model simplification techniques, classifying and doing analogy among these technologies, then we propose two new algorithms of model simplification, the main tasks can be summarized as the following aspects:Firstly, we study and compare the popular simplification algorithms. Different application fields have different demands, so every simplification algorithm has its own character. We pay more attention to the basic two problems: model simplifying method and error controlling method. Besides these, we also compare whether the algorithm can reserve the topology of the model, whether it can produce multi-resolution models, and whether it can deal with the model with arbitrary topology.Secondly, the dissertation proposes a mesh simplification algorithm based on the shape transform of triangles. Based on the Garland's quadric error metrics, the algorithm uses edge collapse as main operations and fully considers the effects of the length of the edge and the shape transform of the triangles after edge collapse, avoiding sharply changing visual features of model and creating narrow triangles; In addition, the algorithm considers the effect of triangles' area around a vertex and gets the average value of quadric error metrics for each vertex, avoiding wrongly choosing collapse edge caused by the error accumulation , and at the same time avoiding the creation of hollows on the model surface which are made by premature simplification of too large area of triangles around the vertex. According to the thesis analysis and experiments' validation, it proves the validity of the algorithm and gets better experiment results.Lastly, we propose a new mesh model simplification algorithm. The algorithm mainly uses vertex pair collapse, and dividing the mesh by quad-tree and limiting the choice of vertex pair to the leaf node, computing the collapse cost of vertex pair based on the quadric error metrics, and making the distance between the viewer and the local area and the area of the triangle as the weight-coefficients, then computing the average quadric error metrics for each vertex. The characteristics of the algorithm are high speed and efficiency, and realizing the model simplification view-dependant and keeping better the simplification quality of 3D model.At last, the dissertation has realized the two algorithms with the VC++. We use mass models to validate it and analyze and do comparisons with the existed algorithm results from time complexity, the simplification quality of models and so on. It is proved the algorithms are available.