| With the development of advanced technologies and improvement of life quality, accurately designed and manufactured artificial prosthesis for sick organ repairing is applied more and more often in modern surgery. This needs to adapt traditional CAD/CAM systems to the particular requirement of bio-medicine application, also will impulse the innovation of CAD/CAM technology itself.The research of this dissertation aims at the development of a medical prosthesis CAD system based on piece-wise subdivision surfaces. Thus, the research objects are the key modeling technologies for the system, from the medical image input to the manufacturing interface output, including medical image three-dimensional reconstruction, triangular mesh processing, subdivision surfaces fitting, subdivision surfaces based solid modeling and rapid prototyping manufacturing interface representation, etc. The main research contents and achievements are as following in detail:(1) An overall architecture of medical prosthesis CAD system based on subdivision surfaces is established, which is described in the two viewports: technological hierarchy and functional modules. The technological hierarchy consistes three levels: fundamental theory, realization tool and clinic applications, which is a good guide for further research. The functional modules describe how to implement the system, which paves the way for the system lasting development.(2) The topology robust and efficient Marching Cube algorithm for medical image 3D reconstruction is implemented. An ambiguity resolved MC algorithm is implemented; to improve the efficiency of the original MC algorithm, the idea of Region Growing Segmentation is put into MC algorithm, and the Neighbor Cubes Tracing based MC algorithm is put forward.(3) The method of triangular mesh smoothing, simplification and shape optimization for subdivision surfaces fitting is implemented. To get the base mesh well shaped and as compact as possible for subdivision surfaces fitting, none available algorithms and software can succeed along. In this dissertation, multi-policies are adopted to achieve the goal. First, a shape optimization item is added to the edge collapse cost computation formula of the original QEM algorithm, and a coefficientαis used for controlling the shape item's effect on the overall cost, the method is calledαShape-QEM simplification algorithm. Second, the Tangent Laplace Smoothing based mesh vertex geometric optimization and the Local Topology Adjusting based mesh topology optimization is integrated into the overall simplification process, thus the Iterative Mesh Simplification and Optimization algorithm is put forward.(4) The Interactive Optimization based Subdivision surface Fitting algorithm is put forward, by which the computational efficiency and fitting accuracy can be balanced best. First, the inputted original mesh M_O is simplified and optimized to base mesh M_B, which is Subdivision Remeshed several times to get M R that fitted to M_O, then M R is subdivision fitted to control mesh M_C, from which the subdivision limit mesh M_∞that fits M_O is gotten.(5) The solid modeling method of"Constructive Solid Boundary Representation with Subdivision Surfaces (CSBrepSS)"is put forward. Using hybrid CSG/Brep representation, the whole solid model is a CSG tree made of leaf nodes with basic Brep, which include triangular mesh, subdivision surface control mesh and basic geometries with parametric representation.(6) A subdivision surfaces based RP interface representation method is put forward. Using the embedded subdivision surface modeling module, RP equipments can read CAD models represented with subdivision control mesh, subdivide the control mesh to generate smooth models with the subdivision rule and feature tags provided in the control mesh, then slice the result mesh and generate machining code. Thus, complex smooth surface can be represented with compact subdivision control mesh, and it paves the way of networked manufacturing of large complex prostheses.
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