Sharp Feature Rendering And Cutting Of Point-based Surfaces

With the increasing complexity of polygonal graphics models and popularization of3D scanner, a trend of directly using points to represent objects has been devel-oped. In the last decade, point-based surface representations have been proven to be a flexible and efficient alternative to mesh-based surface ones. The main advantage of point-based model is that no connectivity information has to be generated and no topo-logical constraints have to be taken care of. To make point-based models fast enough for real-time application, point surfaces are usually rendered by splatting-based methods. However, such methods have difficulty in representing sharp features, which are very critical to many graphics applications, such as CSG modeling and cutting simulation.This thesis presents a novel method for efficiently sharp feature rendering and cut-ting of point-based surfaces, which is based on the point-and-edge model. Compared with normal point-based surfaces, this model involves an extra set of explicit clip line segments to represent sharp features.In order to make this model more suitable for representation and rendering, we separated the surface points into several smooth surfaces and introduced a new algo-rithm for clipping or rasterizing splats, which could produce good and efficient clip-ping results. With this clipping algorithm, no up-sampling is needed and the time-consuming pre-processing step before rendering could be simplified. In addition, we also modified the e-z-buffer method to deal with the artifact problem near sharp fea-tures.With the help of the model and its rendering method, we provided a cutting algo-rithm based on our model. The cutting algorithm consists of several parts. In the first part, the original surface points are separated by the cutting apparatus. In the second part, a new cut surface is created. And in the last part, new sharp features between the original surface and the newly-created cut surface are generated.At the end of this thesis, we test our rendering methods on several point models and the sharp features could be preserved very well during the rendering. We also apply the cutting methods to various examples, and show the quality and flexibility of our approach.