3D reconstruction of polyhedral objects from single parallel projections using cubic corner

This paper presents a direct method to recover the geometry of the 3D polyhedron depicted in a single parallel projection. It uses two sets of information, the list of faces in the object, obtained automatically from the drawing, and a user-identified cubic corner, to compute for the coordinates of the vertices in the drawing and thus establish the 3D geometry of the whole polyhedron. The algorithm exploits the topological structure of the polyhedron, implicit in the connectivities between the faces, resulting in a complexity that is linear in the number of faces. The method is extended to objects with no cubic corners as well. The algorithm works well for recovering objects from accurate line drawings, producing accurate 3D objects. A simple extension to the algorithm allows it to handle inaccurate drawings such as sketches, and produce 3D objects that are consistent with our human perception of the drawings.     

不完全投影数据图像重建的ART算法研究

ART算法是一种经典的图像重建方法,适合于不完全投影数据重建。为了提高重建速度,通常对权因子进行简化,其结果是在重建图像中普遍存在椒盐噪声。提出了一种改善重建质量的方法,在每次迭代后对重建图像进行有选择的平滑,将平滑结果作为下一次迭代的初值,其特点是将图像处理和图像重建相结合。仿真实验表明该方法非常有效,不但提高了重建质量,而且克服了利用Box模板进行平滑所造成的图像模糊现象。     

A Bayesian approach to reconstruction from incomplete projectionsof a multiple object 3D domain

An estimation approach is described for three-dimensional reconstruction from line integral projections using incomplete and very noisy data. Generalized cylinders parameterized by stochastic dynamic models are used to represent prior knowledge about the properties of objects of interest in the probed domain. The object models, a statistical measurement model, and the maximum a posteriori probability performance criterion are combined to reformulate the reconstruction problem as a computationally challenging nonlinear estimation problem. For computational feasibility, a suboptimal hierarchical algorithm is described whose individual steps are locally optimal and are combined to satisfy a global optimality criterion. The formulation and algorithm are restricted to objects whose center axis is a single-valued function of a fixed spatial coordinate. Simulation examples demonstrate accurate reconstructions with as few as four views in a 135° sector, at an average signal-to-noise ratio of 3.3     

Volumetric template fitting for human body reconstruction from incomplete data

In this paper, we present a method for reconstructing 3D human body from incomplete data, which are point clouds captured by inexpensive RGB-D cameras. Making use of the volumetric mesh in a template, the fitting process is robust. This method produces high quality fitting results on incomplete data, which are hard to be offered by the surface fitting based methods. The method is formulated as an optimization procedure, so that the results of volumetric fitting rely on the quality of initial shape (i.e., the shape of template). In order to find a good initial shape, we develop a template selection algorithm to choose a template in an iterative manner by using the statistical models of human bodies. Experimental results show that our method can successfully reconstruct human body with good quality to be used in design and manufacturing applications.     

Bayesian image and pattern reconstruction from incomplete and noisy data

A Bayesian iterative method can be the basis for a wide range of technologies in the field of pattern recognition and image reconstruction. It involves finding the most probable solutions for images or patterns, if functionals describing the likelihood function and a priori information, respectively, are already known. The article describes the basic principles and recent advances in the development of BIM and its applications in various fields, mainly in tomography and restoration of functions from incomplete and noisy data.     

下视SAR数据3维表面重建

目的 合成孔径雷达(SAR)因成像方法、几何角度等原因使得采集到的数据具有稀疏性及残缺性,如果直接用其进行建模,不能真实地还原物体。针对下视SAR数据的特点,提出一种在建模过程中能够自动修补稀疏及残缺数据的重建方法。方法 首先引入大津法对3维SAR数据进行预处理,然后将2维图像分割方法中的Chan-Vese模型推广应用到下视SAR数据的表面重建中,在初始表面及轮廓指示函数的求取过程中引入距离函数和内积函数。结果 将本文方法与等值面抽取法的重建结果进行比较,本文方法在重建的过程中能够自动修补空洞,重建出的模型表面更加光滑,能更加真实地反映原物体的特征。结论 可以将本文方法推广应用到稀疏及残缺SAR数据的建模中。     

Automatic form feature recognition and 3D part reconstruction from 2D CAD data

In this paper, a method which can recognize form features and reconstruct 3D part from 2D CAD data automatically is proposed. First, we use the divide-and-conquer strategy to extract the vertex-edge data from each 2D engineering drawing of IGES format. Then, a set of production rules are developed to facilitate the form feature matching process. A new structure of form feature adjacency graph (FFAG) is devised to record the related attibutes of each form feature. Finally, to avoid the combinatorial subparts composition problem, a sweeping operation and volumetric intersection approach is used to rapidly reconstruct the remaining 3D objects. The last reconstructed 3E object is used as the base of the FFAG. All the recognized form features in the FFAG can be classified as depression or protrusion features on the 3D part base. The FFAG structure can be easily transformed into CSG/DSG structure, which is readily integrated with the downstream CAPP/CAM systems. A detailed example is provided to illustrate the feasibility and effectiveness of the proposed system.     

3D reconstruction of buildings from LiDAR data considering various types of roof structures

In this article, a different approach has been proposed to detect and reconstruct buildings in 3D space. In this regard, some potentially primary features were produced and a genetic algorithm (GA) was employed in order to select the optimum features. The selected features were utilized to detect the building by using k-nearest neighbour (k-NN) algorithm. The detection results were used as inputs of reconstruction procedure. The proposed approach for 3D reconstruction consists of three main steps: roof planes were separated in the first step. Then, the corners of each plane boundary were extracted in order to provide the roof reconstruction possibility. Finally, the walls were reconstructed and merged to roofs and the final 3D model was obtained. Results evaluation indicated that the average value of buildings detection in the test areas was 87.84% in Quality. Moreover, the average value of buildings reconstruction in the test areas was 76.95% in object based Quality, and 95.66% in Quality of building planes that were greater than 25 m², respectively. Also, the average of altimetric and planimetric RMS of the test areas were 0.3 m and 0.75 m, respectively.     

Automated reconstruction of 3D input data for noise simulation

Noise is one of the main problems in urban areas. To monitor and manage noise problems, governmental organisations at all levels are obliged to regularly carry out noise studies. The simulation of noise is an important part of these studies. Currently, different organisations collect their own 3D input data as required in noise simulation in a semi-automated way, even if areas overlap. This is not efficient, but also differences in input data may lead to differences in the results of noise simulation which has a negative impact on the reliability of noise studies. To address this problem, this paper presents a methodology to automatically generate 3D input data as required in noise simulations (i.e. buildings, terrain, land coverage, bridges and noise barriers) from current 2D topographic data and point clouds. The generated data can directly be used in existing noise simulation software. A test with the generated data shows that the results of noise simulation obtained from our generated data are comparable to results obtained in a current noise study from practice. Automatically generated input data for noise simulation, as achieved in this paper, can be considered as a major step in noise studies. It does not only significantly improve the efficiency of noise studies, thus reducing their costs, but also assures consistency between different studies and therefore it improves the reliability and reproducibility. In addition, the availability of countrywide, standardised input data can help to advance noise simulation methods since the calculation method can be adopted to improved ways of 3D data acquisition and reconstruction.     

3D geometry reconstruction from orthographic views: A method based on 3D image processing and data fitting

Industrial esthetic designers typically produce hand-drawn sketches in the form of orthographic projections. A subsequent translation from 2D-drawings to 3D-models is usually necessary. This involves a considerably time consuming process, so that some automation is advisable.     

三维重构中层次性断层数据的处理技术

针对基于层次性断层数据的三维重构,通过引入嵌套矩阵构造嵌套树,再通过构造最小生成树的方法来解决轮廓线相邻层次间的对应问题,并以两轮廓环相互覆盖区域的大小作为约束条件.该方法把基于覆盖的轮廓线对应法和基于全局的轮廓线对应方法结合起来,降低了重构时轮廓拓扑关系判断的复杂性,又能准确的确定轮廓线间的对应关系.     

基于雷达复杂1维距离数据的3维重建算法

基于刚体目标3维运动过程中的几何不变性,可以利用目标上多个散射点在单天线雷达1维距离像序列中的1维距离数据,重建出目标未知的3维结构和运动路径。针对此1维到3维的几何重构问题,提出了一种雷达刚体目标结构和运动的3维重建算法,该算法可利用散射点复杂的1维距离数据进行重建,并且采用非线性优化技术实现了对目标重建参数的捆绑调整(bundle adjustment)。另外,该算法中引入了目标的平移模型,使目标的平移参数能够与旋转参数一并求解,从而避免了距离对准操作的误差对重建精度的影响。仿真实验结果表明,由于重建数据中散射点的数量以及目标3维运动的丰富性得到了显著提高,尤其是最优化技术在算法中的成功应用,重建算法的鲁棒性得到了有效增强。     

3D heart-vessel reconstruction from biplane angiograms

Biplane angiography generates just two time equivalent X-ray images. These X-ray systems can be rotated independently from each other (restricted by possible collisions only). The article explains how highly accurate 3D models of vessel systems can be reconstructed, visualized, and quantitatively evaluated from these X-ray images     

低成本基于多幅图像的三维人体重建

提出一种基于多幅图像的低成本的重建目标三维人体模型的方法。首先建立每幅图像上特征点与原始模型特征点之间的对应关系,然后使用基于径向基函数方法对原始模型进行变形从而获得目标模型并对目标模型应用三种过滤器进行局部修复,最后使用视角无关的方法实现纹理映射和基于顶点混合的方法实现皮肤骨骼运动系统。实验结果表明该方法精度高,实用快捷且成本低廉。     

Photorealistic 3D reconstruction from handheld cameras

One of the major challenges in the fields of computer vision and computer graphics is the construction and representation of life-like virtual 3D scenarios within a computer. The VISIRE project attempts to reconstruct photo-realistic 3D models of large scenarios using as input multiple freehand video sequences, while rendering the technology accessible to the non-expert. VISIRE is application oriented and hence must deal with multiple issues of practical relevance that were commonly overlooked in past experiences. The paper presents both an innovative approach for the integration of previously unrelated experiences, as well as a number of novel contributions, such as: an innovative algorithm to enforce closedness of the trajectories, a new approach to 3D mesh generation from sparse data, novel techniques dealing with partial occlusions and a method for using photo-consistency and visibility constrains to refine the 3D mesh. Tomas Rodriguez was born in Madrid in 1961. Bachelor in Physics and Master in Electronics by the Universidad Complutense de Madrid. He started his career in the private R&D sector in 1987, when he specialized in computer vision and parallel processing systems. In the early nineties he participated in the EVA project; one of the most outstanding traffic monitoring system of the time. For more than 10 years, he has been involved in international research projects within the ambit of EUREKA, ESPRIT, V and VI Framework programmes. During this time, he coordinated eight international projects (CAMELOT, CITRONE, ON-LIVE, SAID, VISIRE, EVENTS, ITALES, HOLONICS) and acted as principal investigator in two additional ones (CITRUS and VICTORIA). Since the early days, he had the opportunity to collaborate with some of the most prestigious research institutions in Europe: Franhoufer Inst., INRIA, CNRS, University of Oxford, University of Lund, DFKI, Siemens C-Lab, Philips Research Labs, etc. Evaluator of R&D projects for the Spanish Ministry for Science and reviewer of international scientific journals, he is currently the R&D manager and coordinator for European projects at Eptron SA. His recent interests include: computer vision, real time software, industrial control, parallel processing, iTV, and mobile technologies, etc.     

基于不完全数据的TAN学习算法

TAN算法是一种针对复杂数据且在实际中具有极强的学习能力的有效算法,它已被广泛应用于数据挖掘、机器学习和模式识别领域。由于现实世界中的数据大多是不完全数据,研究了怎样使TAN有效地从不完全数据中学习。首先,用一种有效的方法直接从不完全数据中估计条件互信息,然后应用估计条件互信息法去扩展基本的TAN算法来处理不相关数据,最后实验比较了扩展的TAN算法和基本的TAN算法。实验结果表明,在大多数不完全数据集合上扩展的TAN算法精确性明显高于基本的TAN算法。虽然扩展的TAN算法时间复杂度高于基本的TAN算法,但在可接受范围之内。此估计条件互信息的方法能够容易地和其它技术相结合来进一步提高TAN算法的性能。     

由单幅二维灰度图像重构物体表面形状*

鉴于目前很少有论文讨论完整的由单幅二维灰度图像重构物体表面形状的算法,包括它的控制参数的估计及算法的实现,介绍了一种完整的SFS算法.它在考虑自遮掩影响的情况下,有效地估计了SFS算法中涉及的各种控制参数,并引入亮度约束、灰度梯度约束和可积性约束,计算出表面高度和表面向量,实现三维重构.与传统的算法相比,本算法无论是在速度还是在精度方面都达到了比较高的水平,具有一定的应用前景.最后还指出了在MATLAB中实现需要注意的问题.     

基于单张图像的三维人脸重建

利用一种基于法线的模型变形方法,从单张图像重建高质量的三维人脸.利用球谐函数和一个初始参考模型计算得到模型上每个顶点的法线,利用法线使参考模型变形.实验结果表明:提出的算法可以从单幅图像重建具有细节的高质量三维人脸.     

Derivation of sky-view factors from lidar data

The use of lidar (light detection and ranging), an active light-emitting instrument, is becoming increasingly common for a range of potential applications. Its ability to provide fine-resolution spatial and vertical-resolution elevation data makes it ideal for a wide range of studies. This article demonstrates the ability of lidar data to measure sky-view factors (ψ_s). The lidar data are used to generate a spatial map of ψ_s, which are then compared against photographically derived ψ_s at selected locations. At each location, three near-surface elevation measurements were taken and compared with collocated lidar-derived estimates. Generally a good agreement was found between the two methodologies, although with decreasing ψ_s, the lidar technique tended to overestimate ψ_s. This can be attributed in part to the spatial resolution of the lidar sampling. Nevertheless, airborne lidar systems can easily map ψ_s over a large area, potentially improving the use of such data in atmospheric and meteorological models.