Three-dimensional Complex Models Quickly Simplify And Interactive Methods

The technique of model simplification is one of the hot topics of computer graphics. It hasshown its broad applications in various directions,such as virtual reality, visualization, realisticrendering, computer vision, and progressive hondssion, etc.In this paper, efficient simplification and interaction techniques of large model are discussed.First, a real-time (or little-preprocess-required ) progressive mesh generahng algorithm ispresented for some applications where the models are required to be modifiable. Then, a novelmodel editing method based on the fast progressive mesh generaing algorithm is proposed. hast,in order to deal with models that are too large to fit in main memory, we present a newsimplifying method based on detail shifting. The main contribuion of this paper includes:1. Presentation of a real-time generating algorithin of progressive mesh for dynamicenvironment. Local error measurement with very little computing cost is taken in stead of globalerror measurement to speed up the algorithm. At the same time, the process of collaPse costsorting is optimised as well.2. Presentation of a novel model editing approach based on progressive-mesh. By theapproach, multiple levels of detail of a model are given at one time. Designer then selects a levelas an active level and a closed region from this level as an editing area. A hannonic map isdefined to embed the editing area of the active level onio a 2D rectangle where interpolation ofeach component of the editing information is computed in the rectangle and is then mapped backto the editing area to give the editing result. The editing result at the achve level could also beautomatically propagated onto all the coarser and finer levels.3. Illustration of an efficient and high quality out-of core simplification algorithm. By theapproach, a uniform samPling to the large model is first performed with statistic informationrecorded simu1taneous1y. The detail distribution of the original model is then acquired based onsuch infOrmation. bot, detail shifting from one part to the other of the initially unifonnlysampled n1odel is performed to show the non-uniform detail distribution. The algorithm greatlyimproves the quality of the result model while the processing tdrie is still linear to the model sizeand the memory cost is also small.4. Implementation of a walking-through system, ViAnal St. Paul Church. The projectconsists of three parts: modeling, rendering and walking-through simulation. As fOr the rendering,portal method is used to accelerate visibility culling, and fOr the walking-through simulation, inorder to improve the sense of reality, the architechture of the building is considered to constrainuser's movement.The thesis is divided into seven chapters. In the first chaPter, several acceleration algorithmsof 3D graphics including levelxifdet8il representation are discussed, where the perfonnancerequiremnt and the proSPech of level-of-detaiI algorithm are described as well. In the secondchaPter, some ekisting algorithms for model simPlification are sununarized and categorized. Areal-time generating algOrithm of progressive mesh fOr dynamic environmnt is investigated inChaPter 3. ChaPter 4 illustrates a novel aPproach for model editing based on pregressive mesh.Chapter 5 explains an efficient nd high quality out-ofcore simPlification method based on detailshifting. In ChaPter 6, the imPlementation of a walkingdriugh system, Vtwal St. Paul Churchis described in brief as an instance. Finally, conclusions are drawn in Chapter 7.