Planar shape matching based on binary tree shape representation

In this paper we suggest a new way of representing planar two-dimensional shapes and a shape matching method which utilizes the new representation. Through merging of the neighboring boundary runs, a shape can be partitioned into a set of triangles. These triangles are inherently connected according to a binary tree structure. Here we use the binary tree with the triangles as its nodes to represent the shape. This representation is found to be insensitive to shape translation, rotation, scaling and skewing changes due to viewer's location changes (or the object's pose changes). Furthermore, the representation is of multiresolution.

In shape matching we compare the two trees representing two given shapes node by node according to the breadth-first tree traversing sequence. The comparison is done from top of the tree and moving downward, which means that we first compare the lower resolution approximations of the two shapes. If the two approximations are different, the comparison stops. Otherwise, it goes on and compares the finer details of the two shapes. Only when the two shapes are very similar, will the two corresponding trees be compared entirely. Thus, the matching algorithm utilizes the multiresolution characteristic of the tree representation and appears to be very efficient.     

Intrinsic Symmetry Detection on 3D Models with Skeleton‐guided Combination of Extrinsic Symmetries

The existing methods for intrinsic symmetry detection on 3D models always need complex measures such as geodesic distances for describing intrinsic geometry and statistical computation for finding non‐rigid transformations to associate symmetrical shapes. They are expensive, may miss symmetries, and cannot guarantee their obtained symmetrical parts in high quality. We observe that only extrinsic symmetries exist between convex shapes, and two intrinsically symmetric shapes can be determined if their belonged convex sub‐shapes are symmetrical to each other correspondingly and connected in a similar topological structure. Thus, we propose to decompose the model into convex parts, and use the similar structures of the skeleton of the model to guide combination of extrinsic symmetries between convex parts for intrinsic symmetry detection. In this way, we give up statistical computation for intrinsic symmetry detection, and avoid complex measures for describing intrinsic geometry. With the similar structures being from small to large gradually, we can quickly detect multi‐scale partial intrinsic symmetries in a bottom up manner. Benefited from the well segmented convex parts, our obtained symmetrical parts are in high quality. Experimental results show that our method can find many more symmetries and runs much faster than the existing methods, even by several orders of magnitude.     

Locomotion with articulated legs in pipes or ducts

Different implementations of remote controlled robots exist that can inspect and repair the interior of a pipe or duct. For this purpose they have video cameras and tools like a welding set or a grinder on board. This paper describes an approach with articulated legs that are pushed against the walls to obtain a grip. In contrast to wheels, for instance, legs overcome problems of common pipe inspection robots, like branches or obstacles in the pipe. The robot has a hierarchical control architecture with reflexive behaviour in the lower layers. In a two-dimensional simulation environment the robot performed successfully in several shapes of pipes. The results show that simple reflexive behaviour is sufficient to overcome even complex shapes. In the tested environment, reflexive behaviour prevented deadlock and ensured the robot's safe operation.     

Environmental Objects for Authoring Procedural Scenes

We propose a novel approach for authoring large scenes with automatic enhancement of objects to create geometric decoration details such as snow cover, icicles, fallen leaves, grass tufts or even trash. We introduce environmental objects that extend an input object geometry with a set of procedural effects that defines how the object reacts to the environment, and by a set of scalar fields that defines the influence of the object over of the environment. The user controls the scene by modifying environmental variables, such as temperature or humidity fields. The scene definition is hierarchical: objects can be grouped and their behaviours can be set at each level of the hierarchy. Our per object definition allows us to optimize and accelerate the effects computation, which also enables us to generate large scenes with many geometric details at a very high level of detail. In our implementation, a complex urban scene of 10 000 m², represented with details of less than 1 cm, can be locally modified and entirely regenerated in a few seconds.     

Computer‐aided virtual reconstruction of Italian ancient clocks

Italy has plenty of cultural heritages. The masterpieces are often placed in locations which are difficult to reach, moreover many artifacts, coming from man's creativity, have very complex functioning. The authors of this paper describe their experience in using the computer graphics capabilities in order to reproduce four ancient clocks functioning coming from different Italian regions. The study is based not only on the 3D‐shapes reconstruction but also on the simulation of their complex mechanisms in order to mimic their functioning. The realism of the reconstruction allows to use the graphical products in exhibits, museums and also for maintenance programs. The rendering techniques together with an accurate camera path, allow to get into the clock mechanisms and to appreciate all the features (and even secrets) that a simple glance cannot reveal. Copyright © 2006 John Wiley & Sons, Ltd.     

A Vision-Based Intelligent System for Packing 2-D Irregular Shapes

Packing two-dimensional shapes on a surface such that no shapes overlap and the uncovered surface area is minimized is an important problem that arises in a variety of industrial applications. This paper introduces an intelligent system which tackles the most difficult instance of this problem, where two-dimensional irregular shapes have to be packed on a regularly or irregularly shaped surface. The proposed system utilizes techniques not previously applied to packing, drawn from computer vision and artificial intelligence, and achieves high-quality solutions with short computational times. In addition, the system deals with complex shapes and constraints that occur in industrial applications, such as defective regions and irregularly shaped sheets. We evaluate the effectiveness and efficiency of the proposed method using 14 established benchmark problems that are available from the EURO Special Interest Group on Cutting and Packing.     

Simple negotiation schemes for agents with simple preferences: sufficiency,necessity and maximality

We investigate the properties of an abstract negotiation framework where agents autonomously negotiate over allocations of indivisible resources. In this framework, reaching an allocation that is optimal may require very complex multilateral deals. Therefore, we are interested in identifying classes of valuation functions such that any negotiation conducted by means of deals involving only a single resource at a time is bound to converge to an optimal allocation whenever all agents model their preferences using these functions. In the case of negotiation with monetary side payments amongst self-interested but myopic agents, the class of modular valuation functions turns out to be such a class. That is, modularity is a sufficient condition for convergence in this framework. We also show that modularity is not a necessary condition. Indeed, there can be no condition on individual valuation functions that would be both necessary and sufficient in this sense. Evaluating conditions formulated with respect to the whole profile of valuation functions used by the agents in the system would be possible in theory, but turns out to be computationally intractable in practice. Our main result shows that the class of modular functions is maximal in the sense that no strictly larger class of valuation functions would still guarantee an optimal outcome of negotiation, even when we permit more general bilateral deals. We also establish similar results in the context of negotiation without side payments.     

Efficient determination of low-frequency normal modes of large protein structures by cluster-NMA

The structure-function relationship is critical to understanding the biologically relevant functions of protein structures. Various experimental techniques and numerical modeling methods, normal mode analysis (NMA) in particular, have been employed to gain insight into this relationship. Experimental methods are often unable to provide all the desired information and comprehensive modeling techniques are often too computationally expensive. The authors build upon and optimize their cluster normal mode analysis (cNMA) tool, which uses embedded rigid-bodies and harmonic potentials to capture the biologically significant, low-frequency, oscillations of protein structures. cNMA represents atomic details with a scalable number of degrees-of-freedom, which can be chosen independent of structure size. This representation overcomes the otherwise quadratic order memory requirements and cubic order computational complexity associated with traditional all-atom NMA. cNMA is two orders of magnitude faster than traditional all-atom NMA when clustering by residue (very high resolution) and in the more traditional application using a fixed number of clusters, cNMA computationally scales as O(n), which is two orders of complexity faster than all-atom NMA. cNMA is presented and very large example structures with up to 10(6) atoms are analyzed on a notebook PC in the time scale of minutes/hours. The resulting mode shapes help identify biologically significant, conformational pathways.     

FP-VTON：基于注意力机制的特征保持虚拟试衣网络

随着互联网经济和人工智能技术的飞速发展,越来越多的消费者选择在网上购买衣服,虚拟试衣技术可以为消费者提供方便、快捷的试衣服务,为消费者提供更好的网上购物体验。当前,基于二维图像的虚拟试衣方法可以摒弃三维虚拟试衣所需昂贵的硬件成本和时间代价,但是仍然存在无法有效适应模特的不同体型及大姿态动作的问题,无法充分保留目标服装复杂纹理特征和局部细节特征的问题。为此,提出一种基于注意力机制的特征保持虚拟试衣网络FP-VTON,通过服装变形和服装融合两阶段网络生成虚拟试穿结果。针对传统卷积难以适应非刚性物体大尺寸变形的问题在两阶段网络中引入了捕捉全局特征的特征注意力机制,针对TPS变换翘曲严重的问题提出了服装保真损失函数对网格上点间的距离和斜率进行约束。通过与相关工作的定量和可视化定性实验对比,充分验证了FP-VTON在大姿态形变、复杂纹理服装和特殊体型的情况下可以生成更加逼真的图像,更加有效地保留服装的复杂纹理细节和用户的身份信息。     

基于V-矩的图像分类算法

基于一类不仅含有连续函数,还含有间断函数的正交完备函数系——V-系统,提 出相应的V-矩函数,并将之应用到图像分类中。V-系统中基函数的间断特性,使得V-矩函数 在描述含有多个闭合边界的形状时有特别的优势,这种优势表现为对这类复杂形状的特征提取 更加准确。因此用V-矩可以得到一种图像分类的有效算法。在几个通用数据库中的图像分类 实验表明,本文算法较Zernike 矩、不变矩和几何中心矩有更高的准确率,对噪声不敏感,特 别在含有多个闭合边界的复杂形状分类问题中,本文方法优势更为显著。     

用优化技术对样条曲面模型的研究

由于样条曲面具有灵活性，概念简单，易于通过操作控制点控制形状，所以样条曲面对于自由基建模具有十分重要的，但是，对于复杂形状，可通过大量控制点和用一些几何规则对曲面进行描述，本文将对有关这些规则描述和建立一些基本概念。     

Computing Size Functions from Edge Maps

Size functions are integer valued functions of two real variables which have been recently proposed for the representation and recognition of shape. A main limitation of the theory of size functions appeared to be the fragility of the produced representation with respect to edge fragmentation. In this paper it is shown that size functions can actually be defined without making assumptions on the topological structure of the viewed shape. Consequently, size functions can be profitably used even in the presence of fragmented edge maps. In order to demonstrate the potential of size functions for computer vision, a system for shape recognition is described and tested on two different domains. The very good performances of the system indicate that size functions are extremely effective for the analysis of shapes for which geometric models might be difficult to obtain.     

Context-aware services based on spatio-temporal zoning and crowdsourcing

Crowdsourcing offers great opportunities to recognise user context and prescribe relevant services for both offline and real-time activities. In this work, we present a zoning model that leverages spatio-temporal dimensions and then employs different contexts to recommend necessary customised services. The context model takes into consideration three context sets: fully restricted, fully unrestricted and semi-restricted with respect to both spatial and temporal dimensions. As a proof of concept, we apply this zoning model in a scenario where a very large crowd get together to perform spatio-temporal activities. The user context of the heterogeneous crowd is captured using the carried smartphones, i.e. via crowdsourcing. Depending on the context sets and zone, the system can recommend a set of services to each user. The system has been deployed since 2014 to support the spatio-temporal activities of a very large crowd. We present our implementation details and the user feedback, which is very encouraging.     

Shape description by time series

Time series modeling techniques are adapted to represent or describe two-dimensional closed contours. Both linear and nonlinear models are fitted. It is found that to detect small changes in shape nonlinear modeling is necessary, even though linear models may be sufficient to differentiate between shapes which differ widely. A nonlinear model called the noncausal quadratic Volterra model is developed for the purpose. Implementation is illustrated with shapes of aircraft     

Extending Superquadrics with Exponent Functions: Modeling and Reconstruction

Superquadrics are a family of parametric shapes which can model a diverse set of objects. They have received significant attention because of their compact representation and robust methods for recovery of 3D models. However, their assumption of intrinsical symmetry fails in modeling numerous real-world examples such as the human body, animals, and other naturally occurring objects. In this paper, we present a novel approach, which is called extended superquadric, to extend superquadric's representation power with exponent functions. An extended superquadric model can be deformed in any direction because it extends the exponents of superquadrics from constants to functions of the latitude and longitude angles in the spherical coordinate system. Thus, extended superquadrics can model more complex shapes than superquadrics. It also maintains many desired properties of superquadrics such as compactness, controllability, and intuitive meaning, which are all advantageous for shape modeling, recognition, and reconstruction. In this paper, besides the use of extended superquadrics for modeling, we also discuss the recovery of extended superquadrics from 3D information (reconstruction). Experiments on both realistic modeling and extended superquadric fitting are presented. Our results are very encouraging and indicate that the use of extended superquadric has potential benefits for the generation of synthetic images for computer graphics and that extended superquadric also is a promising paradigm for shape representation and recovery in computer vision.     

Context-Aware Skeletal Shape Deformation

We describe a system for the animation of a skeleton-controlled articulated object that preserves the fine geometric details of the object skin and conforms to the characteristic shapes of the object specified through a set of examples. The system provides the animator with an intuitive user interface and produces compelling results even when presented with a very small set of examples. In addition it is able to generalize well by extrapolating far beyond the examples.     

Contour-driven Sumi-e rendering of real photos

We propose a sketch-based system for rendering oriental brush strokes on complex shapes. While previous research has focused on methods for converting user-specified trajectories into oriental ink painting (Sumi-e) strokes, we propose an approach that takes as input the contours of complex shapes, estimates automatically the sizes of the brush footprints, their orientations, and the brush trajectory. Then, it renders them into oriental ink paintings. The approach performs in three steps; first complex shapes are decomposed into elementary shapes that can be rendered with a single brush stroke. Second, the brush trajectory estimation is formulated as the minimization of an energy function that measures the quality of the trajectory. Finally, the estimated trajectories are rendered into brush strokes by mapping on them footprint textures scanned from real images. We demonstrate that the proposed contour-driven approach is particularly suitable for converting real images into Sumi-e paintings with minimum interaction. To this end we develop a system where images are either interactively or automatically segmented into elementary shapes and converted into Sumi-e paintings. For the automatic segmentation, we observe that the strokes in Sumi-e paintings are nearly parallel to the edge tangent flow (ETF). We propose a segmentation procedure that is based on clustering the curves obtained by integrating the ETF of real images. Experiments on complex shapes show that the proposed contour-based approach produces a large variety of complex strokes compared to trajectory-based approaches.     

国际化标准框架下蒙文操作系统的设计

蒙文操作系统实现较为复杂的原因在于两个方面:①传统蒙文采用自顶向下竖写、每列从左向右排列的书写方式;②蒙文字符在不同文本上下文中采用变化相当复杂的显现字形.基于操作系统国际化体系结构,从蒙文字符集、蒙文字符的变形显现、蒙文文本的垂直显示、蒙文独特的图形用户界面等多个方面阐述了传统蒙文操作系统实现中面临的难点和技术方案;简要介绍了基于QtKDE桌面系统的实现;最后提出了蒙文操作系统实现仍需要解决的问题.     

Exploiting causal independence in large Bayesian networks

The assessment of a probability distribution associated with a Bayesian network is a challenging task, even if its topology is sparse. Special probability distributions based on the notion of causal independence have therefore been proposed, as these allow defining a probability distribution in terms of Boolean combinations of local distributions. However, for very large networks even this approach becomes infeasible: in Bayesian networks which need to model a large number of interactions among causal mechanisms, such as in fields like genetics or immunology, it is necessary to further reduce the number of parameters that need to be assessed. In this paper, we propose using equivalence classes of binomial distributions as a means to define very large Bayesian networks. We analyse the behaviours obtained by using different symmetric Boolean functions with these probability distributions as a means to model joint interactions. Some surprisingly complicated behaviours are obtained in this fashion, and their intuitive basis is examined.