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1.
目的:利用三维激光扫描仪扫描全牙列模型,对获得的数据进行处理。重构牙颌的三维图形。方法:将获得的三维点云数据进行处理,包括数据平滑、特征提取、数据分割、自由曲面建模等实现牙颌的三维重构。结论:得到牙颌的三维重建数字模型.牙颌模型的建立将极大地提高后期医生设计牙齿的质量与效率。  相似文献   

2.
目的:利用三维激光扫描仪扫描全牙列模型,对获得的数据进行处理,重构牙颌的三维图形。方法:将获得的三维点云数据进行处理,包括数据平滑、特征提取、数据分割、自由曲面建模等实现牙颌的三维重构。结论:得到牙颌的三维重建数字模型,牙颌模型的建立将极大地提高后期医生设计牙齿的质量与效率。  相似文献   

3.
三维扫描技术和基于CT图像的三维重构是目前主流的牙齿建模方法。由于三维扫描技术只能得到牙冠部分的三维数据模型,而被牙龈包裹的牙根数据却无法采集。利用CT图像进行三维重构虽然可以得到完整的牙齿数据模型,但建模耗时长且成本高。针对上述建模方法的不足,提出一种基于牙冠与牙根特征的牙齿建模方法。此方法基于牙体测量数据,建立牙冠与牙根数据间的关联规则,根据Cardinal样条插值和Tangent权的Laplacian网格变形算法进行三维建模。最后将建模结果与原始数据对比,实验证明建模方法高效可行。  相似文献   

4.
本文主要对三维数据点重构曲面网格模型方法进行了综述。从三维数据点集重构曲面一般遵循以下三个步骤:1)重构曲面网格模型;2)网格简化;3)拟合曲面(通常为Bezier,NURBS),其中重构曲面网格为关键的一点,三维数据点集由三维数字化仪采集得到,不同的数字化设备,得到的三维数据点集可能会有差别,重构曲面网格的算法也不尽相同,本文介绍了几种对于不同数据形式,有代表性的重构曲面网格算法。  相似文献   

5.
基于工业CT切片数据的CAD模型重构   总被引:1,自引:0,他引:1  
为了使工业CT(computed tomography)扫描获得的切片数据能够被CAD软件直接处理并进行模型重构,在得到切片轮廓点坐标数据的基础上,提出了用IGES(Initial Graphics Exchange Specification)格式作为边缘轮廓坐标数据和CAD软件交换标准的方法,并采用VC^++设计了IGES格式转换软件。实现了IGES格式文件的生成,并用逆向软件Imageware重构出三维CAD模型,取得了较好的效果。  相似文献   

6.
从点集重构曲面网格方法综述   总被引:1,自引:0,他引:1  
本文主要对三维数据点重构曲面网格模型方法进行了综述。从三维数据点集重构曲面一般遵循以下三个步骤:1)重构曲面网格模型;2)网格简化;3)拟合曲面(通常为Bezier,NURBS),其中重构曲面网格为关键的一步;三维数据点集由三维数字化仪采集得到,不同的数字化设备,得到的三维数据点集可能会有差别,重构曲面网格的算法也不尽相同。本文介绍了几种对于不同数据形式、有代表性的重构曲面网格算法。  相似文献   

7.
以汽车发动机风扇为研究对象,采用ATOS光学测量系统对风扇表面数字化得到其三角网格模型,利用三角网格数据预处理技术、过渡曲面特征提取方法、三维重构及实体造型原理对叶片进行逆向造型,并对重构的模型进行光顺性和精度校检。获得符合设计要求的叶片实体模型。  相似文献   

8.
近年来,深度学习在图像处理中表现显著,因此研究者开始将深度学习用于磁共振成像的重构.现有的深度学习模型需要依赖大量数据进行训练,而医学图像很难获得大量数据,因此,为有效的提高MR成像重构的质量,本文提出一个在小数据集上表现良好的深度学习MRI重构方法.本文对U-Net模型进行改进,结合GoogleLeNet和ResNet的优势,提出了UGR-Net模型,并与数据一致性层结合得到级联的UGR-Net.在多种加速因子下使用3种欠采样模式对脑部复数数据进行欠采样,并对级联CNN网络、级联U-Net模型、新提出的级联UGR-Net重构模型的重构性能进行了比较.实验结果表明,级联UGR-Net在视觉和定量指标上均优于级联CNN模型和级联U-Net模型.  相似文献   

9.
基于Voronoi图的二维地层剖面重构   总被引:2,自引:0,他引:2  
本文着手地质结构几何重构问题的研究,将由地质勘测得到的稀疏异质数据点的几何拓扑信息作为初始数据,重新构造二维地层截面图。重构分三步完成:首先构造输入数据点集的Voronoi图模型,然后合并相邻同质Voronoi多边形,最后对每个地层边界作光顺处理。该算法已成功地运行了许多实例,实验结果显示这种方法非常有效,而且推广到
到三维地质结构重构。  相似文献   

10.
基于小波变换与自回归模型的网络流量预测   总被引:8,自引:1,他引:8  
本文提出一种基于小波变换与自回归模型的网络流量预测方法,将流量数据构成的原始序列进行小波分解,并将分解得到的近似部分和各细节部分分别单支重构到原级别上;对各个重构后的序列建立自回归模型,由所拟合的模型分别进行预测;结合各个重构后序列的预测结果,可以得到对原始序列的预测结果。实验结果表明,这种方法比传统的几种网络流量预测方法具有更高的预测准确度。  相似文献   

11.
Three dimensional reconstruction of coronary arteries from two views   总被引:8,自引:0,他引:8  
Geometric representation and measurements of localized lumen stenosis of coronary arteries are important considerations in the diagnosis of cardiovascular diseases. This discrete narrowing of the arteries typically impairs blood flow in regions of the heart, and can be present along the entire length of the artery. Three-dimensional (3-D) reconstruction of coronary arterial tree allows clinician to visualize vascular geometry. Three-dimensional representation of tree topology facilitates calculation of hemodynamic measurements to study myocardial infarction and stenosis. The 3-D arterial tree, computed from two views, can provide more information about the tree geometry than individual views. In this paper, a 3-step algorithm for 3-D reconstruction of arterial tree using two standard views is presented. The first step is a multi-resolution segmentation of the coronary vessels followed by medial-axis detection along the entire arterial tree for both views. In the second step, arterial trees from the two views are registered using medial-axis representation at the coarsest resolution level to obtain an initial 3-D reconstruction. This initial reconstruction at the coarsest level is then modified using 3-D geometrical a priori information. In the third step, the modified reconstruction is projected on the next higher-resolution segmented medial-axis representation and an updated reconstruction is obtained at the higher resolution. The process is iterated until the final 3-D reconstruction is obtained at the finest resolution level. Linear programming based constrained optimization method is used for registering two views at the coarse resolution. This is followed by a Tree-Search method for registering detailed branches at higher resolutions. The automated 3-D reconstruction method was evaluated on computer-simulated as well as human angiogram data. Results show that the automated 3-D reconstruction method provided good registration of computer-simulated data. On human angiogram data, the computed 3-D reconstruction matched well with manual registration.  相似文献   

12.
对激光三维扫描系统获得的没有任何附加信息的轮廓线点云数据进行处理,首先采用求最大连通域的方法删除噪声点,利用设定相邻点连线夹角正切阈值的方法精简数据,然后采用基于局部切平面簇的方法对数据点云进行切平面的估算、法向量的调整和计算距离函数,用改进的MC方法输出三维网格,并且应用基于顶点的网格删除算法对三维网格进行简化,在估算切平面的时候采用新的估算原则,提高了重建速度,改善了重建效果,所表述的重建流程,成功地解决了激光扫描系统所得轮廓数据点的表面重建问题。  相似文献   

13.
针对带有精确截面信息的有序离散点的三维曲面重构问题,提出了一种NURBS曲面快速重构方法.该方法有效地减少了运算数据量,提高了运算效率,同时改进了传统曲面拟合在处理非均匀截面数据点时曲线曲面形状的失真和运算的不稳定现象,最后应用三维图形标准以及图形函数库在实际系统中验证了该方法的有效性.  相似文献   

14.
We present an approach to identify noncooperative individuals at a distance from a sequence of images, using 3-D face models. Most biometric features (such as fingerprints, hand shape, iris, or retinal scans) require cooperative subjects in close proximity to the biometric system. We process images acquired with an ultrahigh-resolution video camera, infer the location of the subjects' head, use this information to crop the region of interest, build a 3-D face model, and use this 3-D model to perform biometric identification. To build the 3-D model, we use an image sequence, as natural head and body motion provides enough viewpoint variation to perform stereomotion for 3-D face reconstruction. We have conducted experiments on a 2-D and 3-D databases collected in our laboratory. First, we found that metric 3-D face models can be used for recognition by using simple scaling method even though there is no exact scale in the 3-D reconstruction. Second, experiments using a commercial 3-D matching engine suggest the feasibility of the proposed approach for recognition against 3-D galleries at a distance (3, 6, and 9 m). Moreover, we show initial 3-D face modeling results on various factors including head motion, outdoor lighting conditions, and glasses. The evaluation results suggest that video data alone, at a distance of 3 to 9 meters, can provide a 3-D face shape that supports successful face recognition. The performance of 3-D–3-D recognition with the currently generated models does not quite match that of 2-D–2-D. We attribute this to the quality of the inferred models, and this suggests a clear path for future research.   相似文献   

15.
Clinical interventional hemodynamic studies quantify the ventricular function from two-dimensional (2-D) X-ray projection images without having enough information of the actual three-dimensional (3-D) shape of this cardiac cavity. This paper reports a left ventricle 3-D reconstruction method from two orthogonal angiographic projections. This investigation is motivated by the lack of information about the actual 3-D shape of the cardiac cavity. The proposed algorithm works in 3-D space and considers the oblique projection geometry associated with the biplane image acquisition equipment. The reconstruction process starts by performing an approximate reconstruction based on the Cylindrical Closure Operation and the Dempster-Shafer theory. This approximate reconstruction is appropriately deformed in order to match the given projections. The deformation procedure is carried out by an iterative process that, by means of the Dempster-Shafer and the fuzzy integral theory, combines the information provided by the projection error and the connectivity between voxels. The performance of the proposed reconstruction method is evaluated by considering first the reconstruction of two 3-D binary databases from two orthogonal synthetized projections, obtaining errors as low as 6.48%. The method is then tested on real data, where two orthogonal preprocessed angiographic images are used for reconstruction. The performance of the technique, in this case, is assessed by means of the projection error, whose average for both views is 7.5%. The reconstruction method is also tested by performing the 3-D reconstruction of a ventriculographic sequence throughout an entire cardiac cycle.  相似文献   

16.
In mixed-species forests of complex structure, the delineation of tree crowns is problematic because of their varying dimensions and reflectance characteristics, the existence of several layers of canopy (including understorey), and shadowing within and between crowns. To overcome this problem, an algorithm for delineating tree crowns has been developed using eCognition Expert and hyperspectral Compact Airborne Spectrographic Imager (CASI-2) data acquired over a forested landscape near Injune, central east Queensland, Australia. The algorithm has six components: 1) the differentiation of forest, non-forest and understorey; 2) initial segmentation of the forest area and allocation of segments (objects) to larger objects associated with forest spectral types (FSTs); 3) initial identification of object maxima as seeds within these larger objects and their expansion to the edges of crowns or clusters of crowns; 4) subsequent classification-based separation of the resulting objects into crown or cluster classes; 5) further iterative splitting of the cluster classes to delineate more crowns; and 6) identification and subsequent merging of oversplit objects into crowns or clusters. In forests with a high density of individuals (e.g., regrowth), objects associated with tree clusters rather than crowns are delineated and local maxima counted to approximate density. With reference to field data, the delineation process provided accuracies > ∼70% (range 48-88%) for individuals or clusters of trees of the same species with diameter at breast height (DBH) exceeding 10 cm (senescent and dead trees excluded), with lower accuracies associated with dense stands containing several canopy layers, as many trees were obscured from the view of the CASI sensor. Although developed using 1-m spatial resolution CASI data acquired over Australian forests, the algorithm has application elsewhere and is currently being considered for integration into the Definiens product portfolio for use by the wider community.  相似文献   

17.
Processing images acquired by multi-camera systems is nowadays an effective and convenient way of performing 3D reconstruction. The basic output, i.e. the 3D location of points, can easily be further processed to also acquire information about additional kinematic data: velocity and acceleration. Hence, many such reconstruction systems are referred to as 3D kinematic systems and are very broadly used, among other tasks, for human motion analysis. A prerequisite for the actual reconstruction of the unknown points is the calibration of the multi-camera system. At present, many popular 3D kinematic systems offer so-called wand calibration, using a rigid bar with attached markers, which is from the end user’s point of view preferred over many traditional methods. During this work a brief criticism on different calibration strategies is given and typical calibration approaches for 3D kinematic systems are explained. In addition, alternative ways of calibration are proposed, especially for the initialization stage. More specifically, the proposed methods rely not only on the enforcement of known distances between markers, but also on the orthogonality of two or three rigidly linked wands. Besides, the proposed ideas utilize common present calibration tools and shorten the typical calibration procedure. The obtained reconstruction accuracy is quite comparable with that obtained by commercial 3D kinematic systems.  相似文献   

18.
Building Three-Dimensional Object Models from Image Sequences   总被引:3,自引:0,他引:3  
We present the results from a working system designed to reconstruct a complete CAD/CAM surface model for objects that have both smooth and sharp surface boundaries. The input is a sequence of images of the object; the output is a 3-D surface mesh that can be manipulated and rendered with standard CAD/CAM tools. It is now well known that complete surface information (second-order differential surface properties) can be recovered at edges generated by the extremal boundary of a 3-D surface, In this paper we present new results in applying this theoretical framework to many views of a real object to build a complete 3-D model. Our experiments place these multiple frames in a common coordinate system using known motion, if available, or by otherwise automatically computing object motion based on our classification of edges in the reconstruction process. Experimental results are shown for bath real and synthetic data.  相似文献   

19.
Recent advances in range finding techniques have made the task of acquiring surface data for 3-D objects easier and more accurate. With most advanced techniques, range and color data are acquired simultaneously. Since the number of such acquired data is generally very large, a surface model capable of compressing data while maintaining a specified accuracy is required. The objective of this work is to construct a polyhedral representation of input data for surfaces. This representation adapts to local intrinsic surface properties while preserving their discontinuities. In this paper, we present an accuracy-based adaptive sampling and reconstruction technique for hierarchical triangulation of 3D objects. We have developed a parallel algorithm for adaptive mesh generation that recursively bisects mesh elements by increasing the number of mesh nodes according to local surface properties, such as surface orientation, curvature, and color. The recursive subdivision based on such viewpoint-invariant properties yields a hierarchical surface triangulation that is intrinsic to the surface. This approach also satisfies the absolute accuracy criteria, since nodes are generated as required until the entire surface has been approximated within a specified level of accuracy. We have also developed a parallel algorithm that detects and preserves both depth (C0) and orientation (C1) discontinuities, without the formation of cracks which normally occur during independent subdivision. The algorithm has been successfully applied to adaptive sampling and reconstruction of both range and color images of human faces and Japanese antique dolls with fine grained color-texture.  相似文献   

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