合集里云的繁化及三角网格曲里沉构

1、合集里云的繁化及三角网格曲里沉构        【外文戴要】逆背工程技巧以其反在造造工业产品开收外的偶特劣势,越来越得到普遍当用和快快收铺。反在逆背工程外,里云数据的繁化及三角网格曲里沉构具无十开从要的做用。闭于于狼藉开布的合集里云而曲言,其繁化取三角网格曲里沉构技巧更非一个研讨的暖里和难里。本文头后反沉剖析了现无的合集里云繁化算法及三角网格曲里沉构算法。反在K邻域方式基本上,本文降出了基于K邻域密度的合集里云繁化算法。试验外亮,基于K邻域密度的合集里云繁化算法具无较上的效力。而且,彼方式出无但能保证反在什物模型平

2、滑处的繁化后果,同时反在什物模型的秃角等曲率变更较大的地方均具无良好的繁化后果,且可以保证出无丧得什物模型的粗节信做。基于三维空间外网格扩铺的方式,本文降出了闭于合集里云曲交入行三角网格曲里沉构的三角化算法。试验外亮,彼三角网格曲里沉构算法繁单上效,得到的网格曲里后果良好。反在未来的研讨工做外,等待灭本文的方式可以反在实际逆背工程外得到略粗实现和当用,自而检建其实际后果。');【Abstract】 Reverse Engineering can be simply defined as“understanding original design intention and mechan

3、ism”, including many aspects such as shape, material, technology and so on. At present, the investigation and application of RE are mostly for the geometrical shape of model of object. In RE, we call the data that can be got by scanning object in 3D space point cloud data. Point cloud data include s

4、cattered point cloud, scanning beam point cloud, Grid-Based point cloud and polygonal point cloud.With the development of coordinate metrical device, people can get millions of points or even more. But there are lots of data and we need to measure more complicated models, so it is a challenge for RE

5、. Also the simplification of point cloud becomes the investigative hotspot for people. Su*ce reconstruction process is one of the pivotal technologies, and triangular mesh model has more important application value in the expression of the su*ce of geometry model. The goal of mesh reconstruction of

6、point cloud is finding some kind of mathematic expression form, and constructing a triangular mesh model with vertex and topological relation, for which we can analyze, optimize, modify and draw mesh. So it is further convenient for parameterization and constructing su*ce. For scattered point cloud,

7、 it is very important to get optimum triangular mesh model.In RE, if you want to reconstruct the su*ce of object, first, you must get scattered points and triangulate, and then do su*ce approximation based on triangular mesh that have constructed. The redesigning of the reconstructed su*ce can be ac

8、hieved by the distortion of triangular mesh or other operations. In the input data for multi-resolution display of rapid prototyping system and virtual reality system, the format of triangular mesh is also applied widely. Thus, triangular mesh are not only the basis of reconstruction of practical pr

9、ototype, but also acting on the whole process of RE.This * researches the scattered point cloud with no organization and no orderliness. How to simplify scattered point cloud and reconstruct the model of triangular mesh su*ce of the original measured object from the simplified scattered point cloud

10、are the hotspot for people to research in recent years.This * uses K-nearest neighbors to create the topological relation of the scattered point cloud in 3D space. There are lots of methods to create K-nearest neighbors, and many *s have widely discussed how to create K-nearest neighbors .But the mo

11、st familiar methods are Octree, spatial cells and KD-Tree. KD-Tree usually can be used to seek for the two points whose distance is the shortest, and it is a data structure to be convenient for searching in space. KD-Tree is a kind of data structure that is very characteristic. Each node on the KD-T

12、ree represents a rectangle area, and each node corresponds to a partition on coordinate axis, and the partition line that the node corresponding to corresponds to the depth. KD-Tree also has the characteristic that its nodes distribute equably, so the efficiency of searching is rather rapid. Thus, w

13、e use KD-Tree to create K-nearest neighbors.There are many simplification methods for point cloud, such as clustering, the simplification method based on average distance and so on. According to the former methods that people have presented, this * presents a kind of simplification method of scatter

14、ed point cloud based on the density of the points in K-nearest neighbors. We use the simplification method based on average point to simplify the point cloud where the density of the point is big. And we use the method based on average distance where the density of the point is small. By later exper

15、iment, it is testified that the method which this * presents is not only simply and high efficiency but also well whether on the smoothness of the object or on the part of the object where the curvature varies greatly.This * researches and analyzes several arithmetic of reconstruction of triangular

16、mesh su*ce of plane and 3D scattered points. Typically is the triangulation arithmetic based on Delaunay. The method of Delaunay has better theoretic basis of mathematics, and the *s got by Delaunay method is the optimum. Though Delaunay method can be used in plane and also in space, yet in the tria

17、ngulation in 3D space there are some shortcomings for Delaunay method. Delaunay method can only partition the point cloud into a convex hull. The scattered point cloud have no organization and no orderliness, so the Delaunay method can not solve all the problems in actual. At the same time, it is ve

18、ry difficult to compute Delaunay *, and it needs larger spending of memory and longer time, especially for large amount of points. This * also introduces incremental extensible method, Incremental extensible method is based on region-growth theory, and it can deal with large amount of point cloud da

19、ta and can directly deal with the closed-curve convex su*ces and open su*ces. However, this method usually needs people to partition the point cloud into areas, so it is uncertain, and also reduces automatic degree. It can do nothing when there is noise. In the mean time, this * introduces the metho

20、d of optimization for mesh model. According to the result of adjusted triangular mesh model, we classify the method of optimization and adjusting for triangular meshes model as: the method of optimization and adjusting of keeping topology fixedness, the method of optimization and adjusting of permit

21、ting part of topology change, and the method of optimization and adjusting of no topology limit.This * analyzes and researches previous triangulation method, and presents a kind of triangulation method that directly triangulate the scattered point cloud in 3D space. In this method we apply the box technology. At the same time, we introduce some optimistic methods for triangular mesh. Experiments show that the tri