Study On Key Techniques Of Modeling And Rendering Of Complex Scenes

Modeling and rendering method of scenes is one of the most active research fields in Computer Graphics. As more and more high precision and detailed models are required in many applications, it is difficulty to create accurate model and realistic image with traditional modeling and rendering methods on popular hardware platforms. Some new modeling and rendering methods such as Image Based Modeling and Rendering, Point Based Modeling and Rendering, Reverse Engineering are presented recently. Several key techniques in those new methods are discussed in the dissertation. The main research contents and innovations are as follows:(1) Stereo matching between two real images is a key component in IBMR, in this dissertation, we present a new hybrid stereo matching method based on genetic algorithm. The method is composite of two parts: A local window-based stereo matching algorithm is employed to match image rapidly though there are some mismatches in the result. After filtering those mismatches, the genetic algorithm is used to correct those mismatches by global constraints. Additionally, we also analysis another typical stereo matching method which is called cooperative algorithm presented by C. L. Zitnick. By improving the algorithm in three aspects, the computation cost of new algorithm is much lower than Zitnick's algorithm.(2) A new image morphing algorithm based on boundary of regions is presented. The study focus on three key point of image morphing: Features of images are specified conveniently by arbitrary polygons, those polygons also divide the whole image into some sub-regions which are classified into feature regions and non-feature regions. Feature regions contain details of images. In order to get higher quality of morphing, warping functions in feature region are determined only by its own boundary while warping functions in non-feature region are determined by boundary of several non-feature regions. Dividing the polygon region into triangle mesh automatically can not only simplify the warping functions but also reduce the computation cost. The space-variant liner image interpolation is used to reconstruct a high quality image.(3) Reconstructing a mesh surface from a given scatter points has become an important modeling method, most of previous reconstruction method are only based on the coordinate information of the scatter points. We present a new surface reconstruction method based on normal and curvature of sampled surface. Normal and curvature as key features of surface can be computed from the coordinate information of scatter points. Driven by normal and curvature, the mesh surface can be rapidly reconstructed and is also optimized for its detailed maintaining the shape feature.(4) Most of the simplification algorithms use a distance metric as simplification criteria. The distance metric is not good for preserving the shape of the original mesh. In the dissertation, we present a new mesh simplification algorithm based on vertex's normal, which use edge collapse method to reduce the density of meshes. As the normal is useful to enhance the shape description, the algorithm can simplify the mesh while preserving the features of the surface. A model based on mass-spring system is used to optimize the simplified mesh, taking average curvature of the edge of mesh as the tension of the spring, the vertex of the mesh can be optimized and most of feature of original mesh are preserved.