含内部孔洞的面模型虚拟切割仿真研究

【作者】 于素平；

【导师】 王钰；

【作者基本信息】 青岛大学 ， 计算机应用技术， 2008， 硕士

【摘要】 虚拟切割广泛应用于CAD/CAM、生物医学仿真、计算机图形学和虚拟现实等领域中。对于三角面模型的虚拟切割实现简单,效果逼真,实时性较强,应用方便。本文分别对三维面模型的切割、封面以及拼接的算法做了研究和程序实现,并对仿真结果进行了分析。本文主要在传统的Sutherland-Hodgman多边形裁剪算法的基础上,引入顶点移动算法进行切割,该算法在虚拟切割过程中,确保顶点数量的增加量达到最少,因而,运行效率高,实时性好,且无畸形三角面片生成。但由于顶点移动法可能会造成面模型发生形变,因此提出利用网格细分的思想,对切割模型在切割处首先进行网格细分,再采用顶点移动法,从而保证模型的真实性。切割后的面模型会产生“中空”现象,为逼真仿真效果,需要对其进行封面操作。切割交点形成一个多边形区域,对于凸多边形可以利用逐点插入法很快解决三角化问题,但对于凹多边形和内部包含有孔洞的多边形处理起来较为复杂。本文提出去除算法,即对所有的点按照整体剖分然后去除其中的孔洞部分。算法通用性较强,不仅可以处理凹凸多边形,且可以很好的解决孔洞问题。在实际应用中,如虚拟手术中会出现模型拼接操作,本文也对相关拼接算法做了初步研究,提出了两种解决网格拼接的思想——增点拼接和不增点拼接。对增点拼接进行了实现。本课题以VC++6.0和OpenGL为开发工具对上述算法进行了验证,在开发过程中自始至终贯彻了面向对象的编程思想。以虚拟手术中的三维面模型为数据来源,因为其具有面片数量多、几何结构复杂等特点,所以具有一定代表性。程序结果证明,本文提出的移动顶点算法、去除封面算法以及网格拼接算法,切实可行,达到了仿真效果,具有一定的实际应用价值。最后总结了全文的工作,并指出了存在的不足和今后的研究方向。更多还原

【Abstract】 Virtual Cutting is applied in the field of CAD/CAM、Biology Simulation、Computer Graphics and Virtual Reality. Virtual cutting of triangle-facet has simple realization, realistic effect, and is real-time, convenience. In the paper, virtual cutting, the algorithms for face-triangulation and gridding connection are researched and realized with programming, and the simulation results are analyzed.The transferring vertices algorithm is introduced to cut the facet model on the base of traditional Sutherland-Hodgman algorithm. The algorithm makes sure the increment of the number of vertices is the least, so it has high efficiency, good responsiveness and no misshapen triangles. However, the transferring vertices may make the facet model distortion, so gridding subdivision is used to solve the problem. Gridding subdivision is the first step, and transferring vertices are used in the model to keep the shape of the model.It produces "empty" on the cut model, so face-triangulation is necessary. The cutting vertices form a polygon. It is easy for the convex polygon to solve with incremental insertion points. However, for the concave polygon is a little difficult, an algorithm for deleting triangles is presented in the paper. The algorithm has strong universality, not only solving convex and concave polygons, but also the polyhedron including the holes.In the reality, for example, gridding connection is operated in the virtual surgey, so the connection algorithms are studied in the paper, and two ideas about it are presented--adding vertices and no adding vertices. Lastly, adding vertices are realized with programming.This subject is developed with VC 6.0 and object-oriented programming thought is applied in the course of development, using the 3D model in the virtual surgery, because it has many facets and complex structure. The programming results show that the algorithm is effective and good simulation effect, so it has reality application value.At last, this thesis concludes the work of all the paper and points out the deficiencies and the development oriention.更多还原