CN101615304A - A method for generating robust visual shells - Google Patents
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Abstract
一种生成鲁棒的可视外壳的方法,属于三维建模领域。包括如下步骤:获取物体在至少两个不同视点下同一时刻的图像集合;对所述图像集合中的每幅图像进行并行处理,获得轮廓信息并保存;根据所述轮廓信息利用线段加权求交法构建物体的初始线段集合模型;利用线段集合中心线性过滤对初始线段集合模型进行修正得到结果线段集合模型;利用线段集合多边形检测对物体进行表面重建,得到物体的可视外壳。通过加权线段求交,线段集合中心线性过滤与线段集合多边形检测的方法计算物体的可视外壳,克服传统线段求交与表面边界检测不准确的缺点,同时保证算法结果的精确度,增强了算法的鲁棒性。
A method for generating robust visual shells, belonging to the field of 3D modeling. The method comprises the following steps: acquiring an image set of an object at the same time at least two different viewpoints; performing parallel processing on each image in the image set to obtain and save contour information; using a line segment weighted intersection method according to the contour information Construct the initial line segment set model of the object; modify the initial line segment set model by using the linear filter of the line segment set center to obtain the result line segment set model; use the line segment set polygon detection to reconstruct the surface of the object to obtain the visible shell of the object. Calculate the visual shell of the object through the method of weighted line segment intersection, line segment set center linear filtering and line segment set polygon detection, which overcomes the shortcomings of traditional line segment intersection and surface boundary detection, while ensuring the accuracy of the algorithm results and enhancing the algorithm robustness.
Description
【技术领域】 【Technical field】
本发明涉及一种三维建模的方法,尤其是涉及一种生成鲁棒的可视外壳的方法。The invention relates to a method for three-dimensional modeling, in particular to a method for generating a robust visible shell.
【背景技术】 【Background technique】
快速获取物体三维造型技术在计算机视觉、虚拟现实、人工智能、机械制造、数字娱乐和文物保护等领域有着广泛的应用。目前,三维模型获取技术主要有利用建模软件构造三维模型、通过仪器设备获取三维模型以及利用影像序列来重建场景三维模型这三种方法。第一种方法利用建模软件如3DMax、AutoCAD构造三维模型,可以精确地构造虚拟物体和渲染奇特的效果,但相应软件使用复杂,建模周期长;第二种方法利用三维扫描设备获得三维信息,建模精度高,周期短,但设备较昂贵;第三种方法根据影像序列建模,用户只需使用普通数码相机围绕目标对象进行拍摄,通过相片影像信息重建模型,其数据采集设备简单,效率高。因此,基于影像序列的三维重建以其简单的操作,低廉的设备,较高的效率已成为计算机视觉的重要研究对象。Rapid acquisition of 3D object modeling technology has a wide range of applications in the fields of computer vision, virtual reality, artificial intelligence, machinery manufacturing, digital entertainment, and cultural relics protection. At present, the 3D model acquisition technology mainly includes three methods: using modeling software to construct a 3D model, obtaining a 3D model through instruments and equipment, and using image sequences to reconstruct a 3D model of a scene. The first method uses modeling software such as 3DMax and AutoCAD to construct a 3D model, which can accurately construct virtual objects and render strange effects, but the corresponding software is complex to use and the modeling cycle is long; the second method uses 3D scanning equipment to obtain 3D information , the modeling accuracy is high, the cycle is short, but the equipment is more expensive; the third method is based on the image sequence modeling, the user only needs to use an ordinary digital camera to shoot around the target object, and reconstruct the model through the photo image information, the data acquisition equipment is simple, efficient. Therefore, 3D reconstruction based on image sequence has become an important research object of computer vision because of its simple operation, low-cost equipment and high efficiency.
基于二维的影像序列建模是指由物体的一组二维照片上的侧影轮廓信息来重建物体原始模型的技术,其中二维照片的拍摄角度越多,重建结果越逼近真实物体。由于相机视点和侧影轮廓所产生的锥体相交得到的可视外壳把物体包括在内,所以只能得到与真实物体逼近的物体模型。目前基于可视外壳技术的算法主要分为两大类:体素裁剪方法和表面重建方法。Two-dimensional image sequence modeling refers to the technology of reconstructing the original model of the object from the silhouette information of a group of two-dimensional photos of the object. The more shooting angles of the two-dimensional photos, the closer the reconstruction result is to the real object. Since the visible shell obtained by the intersection of the camera viewpoint and the cone generated by the silhouette contains the object, only an object model close to the real object can be obtained. At present, algorithms based on visual shell technology are mainly divided into two categories: voxel clipping methods and surface reconstruction methods.
体素裁剪方法,Martin和Aggarwal最早提出了从不同角度的相机拍摄到的照片生成可视外壳的体素方法。后来,Chien提出了在平行拍摄条件下利用八叉树结构来表示可视外壳的方法,通过八叉树的数据结构存储空间裁剪的体素信息,这种空间表达式能高效地处理空间的分割与存储信息,提高了运算效率。R.Szeliski在Chien的基础下提出来了在任意角度拍摄的八叉树改进算法。但总体上说,基于体素裁剪的方法有以下几个缺点:(1)重建出来的可视外壳精确度较低;(2)时间复杂度,空间复杂度较高,即使在引入八叉树的存储结构后,问题仍然没有得到很好的解决;(3)表面是由相互独立的体素元素间接生成的,相互之间缺乏紧密联系且多数的情况下会产生冗余信息。随着多处理器并行技术的发展,体素剪裁方法可以得到很好的改进。Voxel cropping method, Martin and Aggarwal first proposed a voxel method to generate a visual shell from photos taken by cameras at different angles. Later, Chien proposed a method of using octree structure to represent the visual shell under the condition of parallel shooting. The data structure of octree is used to store the voxel information of spatial clipping. This kind of spatial expression can efficiently deal with the division of space. And store information, improve the operation efficiency. On the basis of Chien, R.Szeliski proposed an improved octree algorithm for shooting at any angle. But generally speaking, the method based on voxel cropping has the following disadvantages: (1) the accuracy of the reconstructed visible shell is low; (2) the time complexity and space complexity are high, even when the octree is introduced (3) The surface is indirectly generated by independent voxel elements, which lack close connection with each other and will generate redundant information in most cases. With the development of multi-processor parallel technology, voxel clipping methods can be well improved.
表面重建方法能够解决体素方法的第3个缺点。Matsuik提出了多边形求交的方法,此算法用相机的拍摄视点与图片上的侧影轮廓线所形成的锥体直接求交生成可视外壳。后来,Franco使用了极线几何与边界检测的方法直接重构物体表面,提高了算法效率。这种方法所包含的工作有:多面体求交运算,多边形求交运算,检测边的运算。根据每个锥体的侧面去切割物体表面,直接记录物体的面信息。这种方法虽然解决了表面之间的连贯性,但随着拍摄照片数量的增多,物体的重建表面会非常复杂。并且大部分表面重建方法的稳定性都会受到边界点的影响,经常会导致重建表面不完整,尤其是当重建的物体有着复杂的拓扑结构时。除此之外在通过表面重建方法建模时,还需要考虑不同的约束条件,例如平滑约束性、遮挡边缘和纹理边缘、部分遮挡、可靠性。The surface reconstruction method can solve the third shortcoming of the voxel method. Matsuik proposed a polygon intersection method. This algorithm uses the cone formed by the camera's shooting viewpoint and the silhouette contour line on the picture to directly intersect to generate a visible shell. Later, Franco used the method of epipolar geometry and boundary detection to directly reconstruct the surface of the object, which improved the efficiency of the algorithm. The work included in this method includes polyhedron intersecting operations, polygon intersecting operations, and edge detection operations. Cut the surface of the object according to the side of each cone, and directly record the surface information of the object. Although this method solves the coherence between surfaces, as the number of photographs increases, the reconstructed surface of the object will be very complicated. And the stability of most surface reconstruction methods will be affected by the boundary points, often resulting in incomplete reconstruction of the surface, especially when the reconstructed object has a complex topology. In addition to this, different constraints need to be considered when modeling by surface reconstruction methods, such as smoothness constraints, occluded and textured edges, partial occlusion, reliability.
【发明内容】 【Content of invention】
有鉴于此,有必要提供一种重建精度高、鲁棒性强的生成可视外壳的方法。In view of this, it is necessary to provide a method for generating visual shells with high reconstruction accuracy and strong robustness.
一种生成鲁棒的可视外壳的方法,包括如下步骤:获取物体在至少两个不同视点下同一时刻的图像集合;对所述图像集合中的每幅图像进行并行处理,获得轮廓信息并保存;根据所述轮廓信息利用线段加权求交法构建物体的初始线段集合模型;利用线段集合中心线性过滤对初始线段集合模型进行修正得到结果线段集合模型;利用线段集合多边形检测对物体进行表面重建,得到物体的可视外壳。A method for generating a robust visual shell, comprising the steps of: acquiring a collection of images of an object at the same moment under at least two different viewpoints; performing parallel processing on each image in the collection of images, obtaining contour information and saving ; Utilize the line segment weighted intersection method to construct the initial line segment set model of the object according to the profile information; use the line segment set center linear filter to correct the initial line segment set model to obtain the result line segment set model; utilize the line segment set polygon detection to reconstruct the surface of the object, Get the visual shell of the object.
通过加权线段求交,线段集合中心线性过滤与线段集合多边形检测的方法计算物体的可视外壳,克服传统线段求交与表面边界检测不准确的缺点,同时保证方法计算结果的精确度,增强了鲁棒性。Calculate the visual shell of the object through the method of weighted line segment intersection, linear filter of line segment set center and line segment set polygon detection method, which overcomes the inaccurate shortcomings of traditional line segment intersection and surface boundary detection, and at the same time ensures the accuracy of the calculation results of the method and enhances the robustness.
优选地,所述视点均匀分布于以物体为中心的水平圆周上,在各视点下采用数码相机拍摄物体图像。Preferably, the viewpoints are uniformly distributed on a horizontal circle centered on the object, and a digital camera is used to capture images of the object under each viewpoint.
优选地,采用canny边缘检测算子的最优阶梯边缘检测算法获得图像的轮廓信息。Preferably, the contour information of the image is obtained by using an optimal ladder edge detection algorithm of a canny edge detection operator.
优选地,构建初始线段集合模型的方法包括如下步骤:Preferably, the method for constructing the initial line segment set model includes the following steps:
对每一个视点下的物体的轮廓,将其离散为点的集合,所述集合中的点都位于物体的轮廓上,构成点轮廓,每一个视点与相应点轮廓构成一个视点锥体;For the contour of the object under each viewpoint, it is discretized into a set of points, and the points in the collection are all located on the contour of the object to form a point contour, and each viewpoint and the corresponding point contour form a viewpoint cone;
视点锥体的一条母线与其他视点锥体相交产生母线线段集,利用线段加权求交法对母线线段集进行处理得到该视点锥体一条母线下的结果集;One bus line of the viewpoint cone intersects with other viewpoint cones to generate a bus line segment set, and the line segment weighted intersection method is used to process the bus line segment set to obtain the result set under one bus line of the viewpoint cone;
将每一个视点锥体中与相应的点轮廓中点的数量相同的所有母线与其他的视点锥体相交后经过与上述步骤相同的处理后的结果集的集合即为物体的初始线段集合模型。Intersect all generatrix lines in each viewpoint cone with the same number of corresponding point outline midpoints and other viewpoint cones, and the result set after the same processing as the above steps is the initial line segment set model of the object.
优选地,所述线段加权求交法包括如下步骤:Preferably, the line segment weighted intersection method includes the following steps:
将母线线段集中的所有线段用具有一维参数的起点和终点表示;Represent all line segments in the set of bus line segments with a start point and an end point with one-dimensional parameters;
定义以母线线段集中最小起点为起点,最大终点为终点的第一线段属于加权线段集,母线线段集包括多个线段组,每一个线段组由母线与一个视点锥体相交得到,线段组的数量与其他视点锥体的数量相同;It is defined that the first line segment whose starting point is the minimum starting point of the bus line segment set and the maximum end point is the end point belongs to the weighted line segment set. The bus line segment set includes multiple line segment groups. Each line segment group is obtained by the intersection of the bus line and a viewpoint cone. The line segment group The number is the same as the number of other view frustums;
设定一临时集为空;set a temporary set to empty;
检查一个线段组中的每一条线段与加权线段集中的所有线段是否重叠,如果重叠,将重叠结果插入临时集,并将与该重叠结果关联的加权计数器加一;checks whether each segment in a segment group overlaps all segments in the weighted segment set, and if so, inserts the overlapping result into the temporary set and increments the weighting counter associated with the overlapping result;
根据所述临时集将加权线段集更新,并清空临时集;updating the weighted line segment set according to the temporary set, and emptying the temporary set;
逐个处理每个线段组,直到母线线段集中所有的线段均被处理完;Process each line segment group one by one until all the line segments in the bus line segment set are processed;
从最终的加权线段集中选取加权计数器最大的线段构成结果集。Select the line segment with the largest weighted counter from the final weighted line segment set to form the result set.
优选地,更新加权线段集的步骤包括:Preferably, the step of updating the weighted line segment set includes:
若加权线段集中的线段与临时集中的线段有重叠,则将该线段的重叠部分去除形成新的线段,否则保留;If the line segment in the weighted line segment set overlaps with the line segment in the temporary set, remove the overlapping part of the line segment to form a new line segment, otherwise keep it;
将上述处理的线段集合与临时集合并。Merge the collection of line segments processed above with the temporary collection.
优选地,表面重建包括如下步骤:Preferably, surface reconstruction includes the following steps:
将初始线段集合模型中的线段根据法向量进行分类;Classify the line segments in the initial line segment set model according to the normal vector;
同一类线段中根据线段共面的情况获得一组平面,各平面根据截距的不同进行区分;In the same type of line segment, a set of planes is obtained according to the coplanarity of the line segments, and each plane is distinguished according to the intercept;
相邻的平面相交得到边界;Adjacent planes intersect to obtain boundaries;
相邻边界相交得到顶点,由顶点构成用于表面重建的多边形;Adjacent boundaries are intersected to obtain vertices, which form polygons for surface reconstruction;
重复处理初始线段集合模型中的所有线段。Repeat for all segments in the initial segment set model.
【附图说明】 【Description of drawings】
图1为视点锥体相交的示意图;Fig. 1 is a schematic diagram of viewpoint cone intersection;
图2为生成可视外壳的流程图;Fig. 2 is a flowchart of generating a visual shell;
图3为构建物体初始线段集合模型的流程图。Fig. 3 is a flowchart of constructing an initial line segment set model of an object.
【具体实施方式】 【Detailed ways】
本实施例中,生成可视外壳的方法包括如下步骤:In this embodiment, the method for generating a visual shell includes the following steps:
S1:获取物体在至少两个不同视点下同一时刻的图像集合。此步骤用于采集所需建模的物体原始信息,采集的视点越多信息量越大,重建精度越高,本实施例采集视点为12个。各视点的图像采集工具采用普通的数码相机即可。各视点均匀分布于以物体为中心的水平圆周上。同一时刻,物体从12个不同的视点拍摄,取得一个图像集合。S1: Obtain a collection of images of an object at the same moment from at least two different viewpoints. This step is used to collect the original information of the object to be modeled. The more viewpoints collected, the greater the amount of information and the higher the reconstruction accuracy. In this embodiment, 12 viewpoints are collected. An ordinary digital camera can be used as the image acquisition tool of each viewpoint. The viewpoints are evenly distributed on a horizontal circle centered on the object. At the same moment, the object is photographed from 12 different viewpoints to obtain an image collection.
S2:对图像集合中的每幅图像进行并行处理,获得轮廓信息并保存。在这个步骤中,采用边缘检测算法处理得到图像的轮廓信息。图像的边缘是指图像局部区域亮度变化显著的部分,图像的边缘部分集中了图像的大部分信息,确定与提取图像边缘对于整个图像场景的识别与理解是非常重要的。本实施例采用canny边缘检测算子的最优阶梯边缘检测算法获得图像的轮廓信息。具体包括:S2: Parallel processing is performed on each image in the image collection to obtain contour information and save it. In this step, the edge detection algorithm is used to process the contour information of the image. The edge of the image refers to the part of the image where the brightness of the local area changes significantly. The edge part of the image concentrates most of the information of the image. Determining and extracting the edge of the image is very important for the recognition and understanding of the entire image scene. In this embodiment, the optimal ladder edge detection algorithm of the canny edge detection operator is used to obtain the contour information of the image. Specifically include:
S202:用高斯滤波器平滑图像。S202: Smooth the image with a Gaussian filter.
S204:用一阶偏导的有限差分来计算梯度的幅值和方向;S204: Using the finite difference of the first-order partial derivative to calculate the magnitude and direction of the gradient;
S206:对梯度幅值进行非极大值抑制;S206: performing non-maximum suppression on the gradient amplitude;
S208:用双阈值算法检测和连接边缘。根据上述方法得到图像的轮廓信息后保存,用于进一步的处理。S208: Detect and connect edges with a double-threshold algorithm. The contour information of the image is obtained according to the above method and saved for further processing.
S3:根据轮廓信息利用线段加权求交法构建物体的初始线段集合模型。详细的步骤如下:S3: Construct the initial line segment set model of the object by using the line segment weighted intersection method according to the contour information. The detailed steps are as follows:
S302:取得一个轮廓,将轮廓离散为点的集合,构成点轮廓。每一个视点与相应的点轮廓构成一个视点锥体。S302: Obtain a contour, and discretize the contour into a set of points to form a point contour. Each viewpoint and corresponding point outline form a viewpoint cone.
S304:视点锥体的一条母线与其他视点锥体相交得到母线线段集。母线与其他视点锥体中某一个视点锥体相交可能得到一个点,也可能得到一条线段或多条互不重叠的线段。如图1所示,为以视点A为顶点的视点锥体的一条母线l与其他视点锥体中某一个视点锥体相交的示意图。母线l与该视点锥体相交产生两条线段l1、l2,形成线段组S1={l1、l2}。该母线l与所有其他的视点锥体相交即生成该母线l下的母线线段集{Si}i=1 N,本实施例中,N=11,即母线l与其他11个视点锥体相交,因此母线线段集为{S1、S2、......、S11},包括11个线段组。S304: A generatrix of the viewpoint cone intersects with other viewpoint cones to obtain a generatrix line segment set. Intersecting a generatrix with one of the other viewpoint cones may result in a point, or a line segment or multiple non-overlapping line segments. As shown in FIG. 1 , it is a schematic diagram in which a generatrix l of a viewpoint cone with viewpoint A as the vertex intersects with a certain viewpoint cone among other viewpoint cones. The intersection of the generatrix l and the viewpoint cone produces two line segments l 1 , l 2 , forming a line segment group S 1 ={l 1 , l 2 }. The bus line l intersects with all other viewpoint cones to generate the bus line segment set {S i } i=1 N under the bus line l. In this embodiment, N=11, that is, the bus line l intersects with other 11 viewpoint cones , so the bus line segment set is {S 1 , S 2 , ..., S 11 }, including 11 line segment groups.
S306:利用线段加权求交法对母线线段集进行处理得到该视点锥体一条母线下的结果集。母线线段集{S1、S2、......、S11}中,S1至S11相互之间,利用线段加权求交法对母线线段集进行处理得到该母线l下的结果集,线段加权求交方法的核心思想是将多组处于同一直线上的所有线段相互之间重叠次数最多的部分表示出来。该结果集中可能只有一条线段,也可能有多条线段。S306: Using the line segment weighted intersection method to process the bus line segment set to obtain a result set under one bus line of the viewpoint cone. In the bus line segment set {S 1 , S 2 , ..., S 11 }, between S 1 and S 11 , use the line segment weighted intersection method to process the bus line segment set to obtain the result under the bus line l Set, the core idea of the weighted intersection method of line segments is to represent the part with the most overlap among all line segments of multiple groups on the same straight line. There may be only one line segment in the result set, or there may be many line segments.
S308:将结果集加入初始线段集合。S308: Add the result set to the initial line segment set.
S310:检查自视点引向的点是否是其所在点轮廓上的处理的最后一个点。若是,则进行下一步处理,若不是,返回至S304。S310: Check whether the point directed from the view point is the last point processed on the outline of the point where it is located. If yes, proceed to the next step, if not, return to S304.
S312:检查所处理的轮廓是否是最后一个轮廓。若是,则表示初始线段集合添加完毕,若不是,则返回S302。S312: Check whether the processed contour is the last contour. If yes, it means that the initial line segment set has been added, if not, return to S302.
S314:获得初始线段集合模型。S314: Obtain an initial line segment set model.
上述的S306的步骤中,示例算法如下:In the above step of S306, the example algorithm is as follows:
将母线线段集{Si}i=1 N中所有的线段用具有一维参数的起点和终点表示。因为母线线段集中所有的线段都位于母线上,因此其在空间中方向一样,所以可以只用具有一维参数的起点和终点表示一条线段。其中
S602:找到aik中的最小值a0,bik中的最大值b0。用[a0,b0]表示第一线段,且该第一线段属于加权线段集SOLSS,即SOLSS={[a0,b0]}。元素计数器M=1,记录加权线段集SOLSS中的元素个数。S602: Find the minimum value a 0 in a ik and the maximum value b 0 in b ik . The first line segment is represented by [a 0 , b 0 ], and the first line segment belongs to the weighted line segment set S OLSS , that is, S OLSS ={[a 0 , b 0 ]}. The element counter M=1, records the number of elements in the weighted line segment set S OLSS .
S604:选择一个线段组,如S1。S604: Select a line segment group, such as S 1 .
S606:取该线段组中的一条线段,如[a11,b11]。设定临时集S为空集,即 S606: Take a line segment in the line segment group, such as [a 11 , b 11 ]. Set the temporary set S as an empty set, namely
S608:检查S606中所取线段与加权线段集SOLSS中的所有线段是否有重叠。所述重叠是指两条线段中某条线段的起点和/或终点处于另一条线段上。如果重叠,则将重叠的结果插入临时集S,将与该重叠结果关联的加权计数器加1,并将加权线段集SOLSS中涉及重叠的线段去除该重叠结果后也插入该临时集S。如[a11,b11]=[2,4],[a0,b0]=[1,9],则重叠结果为[2,4],与[2,4]关联的加权计数器加1。S608: Check whether the line segment taken in S606 overlaps with all the line segments in the weighted line segment set S OLSS . The overlapping means that the starting point and/or the ending point of one of the two line segments is on the other line segment. If it overlaps, then insert the overlapping result into the temporary set S, add 1 to the weighted counter associated with the overlapping result, and insert the overlapping line segment in the weighted line segment set S OLSS into the temporary set S after removing the overlapping result. Such as [a 11 , b 11 ]=[2,4], [a 0 , b 0 ]=[1,9], then the overlapping result is [2,4], and the weighted counter associated with [2,4] adds 1.
S610:更新加权线段集SOLSS。删除S608中加权线段集SOLSS中涉及重叠的线段,并将临时集S与加权线段集SOLSS合并得到新的加权线段集SOLSS。根据新的加权线段集中线段的条数M,按照起点从小到大的顺序编排线段[a0,b0]、[a1,b1]、......、[aM,bM]。如S608示例中的处理结果为SOLSS={[1,2]、[2,4]、[4,9]},其中[2,4]的加权计数器数值为1,[1,2]和[4,9]的加权计数器的数值为0。S610: Updating the weighted line segment set S OLSS . Delete overlapping line segments in the weighted line segment set S OLSS in S608 , and merge the temporary set S with the weighted line segment set S OLSS to obtain a new weighted line segment set S OLSS . According to the number M of line segments in the new weighted line segment set, arrange the line segments [a 0 , b 0 ], [a 1 , b 1 ], ..., [a M , b M ] in ascending order of starting point ]. As in the example of S608, the processing result is S OLSS ={[1, 2], [2, 4], [4, 9]}, where the weighted counter value of [2, 4] is 1, [1, 2] and The value of the weighted counter for [4, 9] is 0.
S612:检查是否是线段组中最后一条线段。若不是,则转入步骤S606;若是,则进行下一步。S612: Check whether it is the last line segment in the line segment group. If not, go to step S606; if yes, go to the next step.
S614:检查是否是最后一个线段组。若不是,则转入步骤S604;若是,则进行下一步。S614: Check whether it is the last line segment group. If not, go to step S604; if yes, go to the next step.
S616:从上述处理的结果SOLSS中选取加权计数器最大线段构成结果集。S616: Select the largest line segment of the weighted counter from the result S OLSS of the above processing to form a result set.
图像点轮廓包括紧密相邻的点,从视点到点轮廓上的点的射线集合同样是紧密相邻。通过加权线段求交的方法可以有效地计算出一条射线和其他锥体的相交后所得的结果集,对点轮廓的所有射线计算得到的结果集的集合应该是规则的紧密排列,而通过加权线段求交的方法计算一条射线中的线段集合的近似交集结果会受到噪声的影响产生偏差,所以有必要对其进行修正。The image point outline includes closely adjacent points, and the set of rays from the viewpoint to points on the point outline is also closely adjacent. The method of intersecting weighted line segments can effectively calculate the result set obtained by the intersection of a ray and other cones. The set of result sets calculated for all rays of the point profile should be regularly arranged closely, and by weighted line segments The intersection method to calculate the approximate intersection of the line segment set in a ray will be affected by noise and produce deviations, so it is necessary to correct it.
S4:对初始线段集合模型进行修正得到结果线段集合模型。该修正方法是中心线过滤法,其针对的对象是一个视点下所有母线线段集经处理后的结果集的集合。S4: Correct the initial line segment set model to obtain the result line segment set model. The correction method is a centerline filtering method, and its object is the set of processed result sets of all bus line segment sets under a viewpoint.
假如{Si}i=1 N(N为线段个数,Si是第i条线段)是一组线段集合,并且Si=[ai,bi],其中ai≤bi,这组线段集合的中心线性过滤器{S′i}i=1 N:If {S i } i=1 N (N is the number of line segments, S i is the i-th line segment) is a set of line segments, and S i =[a i , b i ], where a i ≤ bi , this Central linear filter {S′ i } i=1 N of set of line segments:
li=bi-ai;表示Si的长度l i =b i -a i ; indicates the length of S i
a′i=(bi+ai)/2-l′i/2;重新确定的起点。a' i = ( bi + a i )/2-l' i /2; re-determined starting point.
b′i=(bi+ai)/2+l′i/2;重新确定的终点。b' i = ( bi + a i )/2+l' i /2; re-determined end point.
如果直接使用
S5:利用结果线段集合模型对物体进行表面重建。如果一个光锥平面对于多个视点可见,则该光锥平面会相交于多个可见视点下的视点锥体,显然只有它们的交集才会落在最终的多面体可视外壳的内部。该光锥平面与其他所有相片锥体相交得到的多边形即为物体的可视外壳信息。本实施例中采取上述原理进行表面重建,具体步骤包括:S5: Using the resulting line segment set model to reconstruct the surface of the object. If a light cone plane is visible to multiple viewpoints, the light cone plane will intersect the viewpoint cones under multiple visible viewpoints, and obviously only their intersection will fall inside the final polyhedral visible shell. The polygon obtained by intersecting the light cone plane with all other photo cones is the visible shell information of the object. In this embodiment, the above principles are adopted for surface reconstruction, and the specific steps include:
S502:将初始线段集合模型中的线段根据法向量进行分类,即法向量相近的线段分为一类,应用中可设定一个阈值,作为判断法向量相近的标准。S502: Classify the line segments in the initial line segment set model according to the normal vectors, that is, the line segments with similar normal vectors are classified into one category, and a threshold can be set in the application as a criterion for judging the similar normal vectors.
S504:对处于相同类的所有线段,计算该线段集合所产生的平面组。所有法向量相同的线段共面构成该平面组中的一个平面,并根据平面的截距对平面进行区分。S504: For all line segments in the same class, calculate the plane group generated by the set of line segments. All line segments with the same normal vector are coplanar to form a plane in this plane group, and the planes are distinguished according to the intercept of the plane.
S506:对每一个平面查找与其相邻的平面,相邻的平面相交得到边界。S506: Search for each plane adjacent to it, and intersect the adjacent planes to obtain a boundary.
S508:相邻的边界相交得到顶点,顶点按次序连接得到用于表面重建的多边形。S508: Adjacent boundaries intersect to obtain vertices, and the vertices are connected in sequence to obtain polygons for surface reconstruction.
S510:处理下一个同类线段集合直到所有的线段都处理完成,即可得到物体的可视外壳。S510: Processing the next set of similar line segments until all the line segments are processed, then the visible shell of the object can be obtained.
以上所述实施例仅表达了本发明的一种实施方式,其描述较为具体和详细,但并不能因此而理解为对本发明专利范围的限制。应当指出的是,对于本领域的普通技术人员来说,在不脱离本发明构思的前提下,还可以做出若干变形和改进,这些都属于本发明的保护范围。因此,本发明专利的保护范围应以所附权利要求为准。The above-mentioned embodiment only expresses one implementation mode of the present invention, and its description is relatively specific and detailed, but it should not be understood as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.
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CN103679815B (en) * | 2013-12-19 | 2017-01-25 | 北京北科光大信息技术股份有限公司 | Visible shell generation method and device based on surface search |
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