The Algorithm Research Of LOD Model Simplification

LOD model is an effective 3D entity representation and it is widely used in computer graphics, Virtual Reality, Geographic Information System and medical image system. The structures of the model in those fields are more precise and more complex. However, such complex model is difficult to store, and is rended slowly. This problem has been the bottleneck of real-time rendering and the transmission. To solve the problem, the models are often simplify by the LOD model simplification technology, and has made great achievements. But, due to the different emphasises of the every LOD model simplification algorithm considered, it has never been able to keep the precision and the speed of the balance. Therefore it is useful to research and develop a new highly efficient LOD model simplification algorithm. Because of the terrain model is more complex and the amount of the data in model is larger, and it is used widely, so it is more meaning to simplify and generate the model.Based on the LOD model simplification related technology research, this paper presents a new LOD model simplified algorithm and an efficient algorithm for terrain simplification. In this paper, some have completed the following tasks:1. At present, many model simplified algorithms could not guarantee the visual characteristics of the simplified model, resulting in serious visual distortion. To solve the issues, this paper presents a LOD model simplified algorithm, which solves the reflection of the vertex Convexo-Concave attribute by introducing the vertex curvature attribute factor , and maintains the geometry features of the model commendably by restriction the creation of long-narrow triangular, and keeps the texture features of model by signing the triangular whose color has changed distinctly, and resolves the visual affection of the error accumulation by computing the data which in both the queue storing the edge collapse costs and the queue noting the changes of edges, so that maintains the visual characteristics of the simplified model.2. The practical applications indicate that the three factors of the vertex curvature, the awareness intensity, and the viewpoint traveling speed have the very important influence to the LOD terrain rendering, but the traditional LOD terrain rendering algorithm does not consider the above factors comprehensively. Therefore, this paper quantifies the three factors, and integrates them into the node evaluation function, then proposes a new algorithm. The experiment has utilized the GPU characteristic fully. GPU carries out the computation of each factors, it storages the vertex which are used frequently and the triangle data which are invariable during several frames to the Video Memory.In this paper, the experiment uses Windows XP, use the Visual C + + and DirectX. The experimental results show that the method proposed in this paper maintains the visual characteristics of LOD model simplification algorithm, efficient, reliable, and is able to maintain a model of good visual features. The proposed view-dependent LOD terrain generation algorithm can be real-time. The algorithm is more efficient to render the terrain.