Three-dimensional Surface Modeling Based On Ct Data And Applications

Surface Modeling is an important subject in Computer Aided Geometric Design and Computer Graphics. It researches on denoting, designing, displaying and analyzing of surface in the environment of computer image system. With the better local characteristic and the flexible shape controlling method, B-spline surface is now used more widely in aviation , mobile and other traditional industry. In this thesis, we use surface modeling into medical visualization domain to describe the 3D model of skin and skull surface and discuss relational operations. These methods have been used into the Skin Restoring from Skull with Computer Aid System that is a project of Ninth five-year-plan of native, and got well effect from the application.In chapter 1,we introduce the history and actuality of Surface Modeling and the theory of skin restoring in medical jurisprudence. We also refer parameter denotation and basic formulary of curve and surface as the theory basis for Surface Modeling. The thesis tells surface analysis method including curvature analysis and curve depth analysis that we using in the skin restoring project.In chapter 2, it tells the definition of B-spline curve and surface and the fundamental algorithm - de Boor algorithm for points of curve and surface. As to reconstruct surface from CT data, we discuss some basic algorithm and introduce the wrapping skin algorithm.In chapter 3,we discuss surface restoring method based on CT data which uses the intersection algorithm between spline curve and radial to resample the section curve, then works out surface controlling point array; take OpenGL to display the surface with reality and the lighting, coloring effect. To improve the 3D displaying effect, we use the amalgamation and anti-twist techs. This chapter still introduces the data structure we have used and the Frankfurt Plane, which is defined in anthropology and so on. We also discuss multi-density surface and gradual morphing surface, demonstrate the advantage of spline surface in restoring skin.Because there are local rough phenomena in the 3D surface, we take the method of combining auto smooth and interactive smooth to solve the problem in chapter 4. In auto smooth method, we use the curvature and depth analysis to look for "bad point" automatically, and take the latitudinal curve to modify the surface; referring to the tech of image processing, we import a interactive method to smooth surface based on image smoothing. And we give out the multi-resolution representation method of curve and surface and the spline wavelet smoothing method.Aimed at Skull restoring surface, we discuss 3D surface editing technology and give corresponding examples including region exception disposal of surface, mirror editing, surface dragging and so on in chapter 5. The surface-dragging problem contains two different dragging methods for discrete surface and continuum surface. At last with the editing on surface, the thesis tells a FFD free distortion method.Under the environment of skin restoring system and the process of disposal CT data, this thesis brings forward new methods on surface reconstruction, surface smoothing and surface editing and therefore researches on it. The outcomes of putting these new methods into practice prove that these methods are of great value.