Mathematical morphological operations of boundary-represented geometric objects

The resemblance between the integer number system with multiplication and division and the system of convex objects with Minkowski addition and decomposition is really striking. The resemblance also indicates a computational technique which unifies the two Minkowski operations as a single operation. To view multiplication and division as a single operation, it became necessary to extend the integer number system to the rational number system. The unification of the two Minkowski operations also requires that the ordinary convex object domain must be appended by a notion of inverse objects or negative objects. More interestingly, the concept of negative objects permits further unification. A nonconvex object may be viewed as a mixture of ordinary convex object and negative object, and thereby, makes it possible to adopt exactly the same computational technique for convex as well as nonconvex objects. The unified technique, we show, can be easily understood and implemented if the input polygons and polyhedra are represented by their slope diagram representations.     

Collision-free object movement using vector fields

Presents a technique for automatically providing animation and collision avoidance in a general-purpose computer graphics system. The technique, which relies on an expanded notion of vector fields, allows users to set up and animate objects easily, then prevents objects from colliding as the animation proceeds. This technique automatically generates volume octree vector fields around objects in a scene. These vector fields affect object motion and animation, and also provide for automatic collision avoidance for arbitrary objects. Applications of collision avoidance in an animation system encompass any scene containing object movement above or around other objects     

New bounds on the number of frictionless fingers requied to immobilize

Using a novel second-order mobility theory that was recently developed by the authors, this article develops new lower bounds on the number of frictionless fingers required to immobilize generic planar objects. We show that any generic smooth or polygonal planar object can be immobilized with three convex fingers or fixtures that have sufficiently flat curvature. Further, if it is possible to specify the fingertip curvature, then any generic smooth or polygonal object can be immobilized with two, possibly concave, fingers. © 1995 John Wiley & Sons, Inc.     

A Smooth Concurrency Revolution with Free Objects

In this paper, the author propose viewing a program as a collection of "free" objects, each of which has its own thread of control and executes its operations within atomic transactions. Such objects would communicate by asynchronous message passing with futures - objects that encapsulate the results of server invocations and let clients retrieve them while hiding the actual state of readiness from the client. Except for the unleashing of newly created free objects, there's no need for specific language constructs other than those already available in 00 languages. After all, C++ has been successful in part because it looked like C, Java has been successful in part because it looked like C++, and C# looks like both. With free objects, the program looks exactly like a traditional OO program, with one exception: certain object creations fork new activity threads and must be distinguished as such. This column discusses how to do that.     

运动视频对象分割的一种快速算法

为了能够实时地对运动视频对象进行分割,提出了一种对视频序列图象中的运动对象进行快速分割提取的算法,该算法首先对图象进行滤波,并求出连续两帧图象之间的差分,然后应用“同化填充”技术和基于对象的“整体运动估计”来对差分图象进行修正,进而得到对象模板,同时利用模板缓冲区的帧间迭代来维持模板的完整性,该算法不仅不依赖于固定背景,而且能够消除差分图中的显露背景,还能得到运动目标较为精确的形状,并且算法简单,快速,鲁棒性好。     

基于可信计算平台的可信动态客体监管系统的设计与实现

大部分安全操作系统在处理客体时,没有区分具体的客体类型,均采用统一的方法进标识,而且多数安全操作系统中采用传统访问控制方法保护的客体均是静态客体,忽略了对动态客体的保护,使得黑客或攻击者可以进行欺骗和中间人攻击,因此,安全操作系统中的动态客体并不可信.首先分析了操作系统中客体的类型,提出了可信动态客体的概念,并分析了其特点.为了防止动态客体泄露信息,提出了基于TPM的可信动态客体监管系统.一方面,该系统要求主体必须在TPM中注册,确保主体身份合法性,才能利用可信动态客体进行信息传递;另一方面,在TPM中必须存储创建该可信动态客体的属主的身份信息,以确保可信动态客体身份的合法性.最后进行了安全和性能分析,分析表明该可信动态客体监管系统可以阻止黑客利用动态客体进行欺骗和中间人攻击,防止信息泄露,为进一步建立可信计算环境提供了基础.     

Polyhedral Objects Metamorphosis Using Convex Decomposition and Morphology

A new technique is presented for computing continuous shape transformations between polyhedral objects. The polyhedron shape transformations can be divided into polyhedron metamorphosis and bi-directional local rigid body rotation transformation. By decomposing two objects into sets of individual convex sub-objects respectively, and establishing the matching between two subsets, the approach can solve the metamorphosis problem of two non-homotopic objects (including concave objects and holey objects). Compared with other methods, this metamorphosis algorithm can be executed automatically for arbitrary polyhedrons and no need user interaction. The user has the ability to choose an automatic matching or to select interactively pairs of corresponding matching convex subsets to obtain special effects. Experiments show that this method can generate natural, high-fidelity, eye-pleasing metamorphosis results with simple computation.     

What Is the Set of Images of an Object Under All Possible Illumination Conditions?

The appearance of an object depends on both the viewpoint from which it is observed and the light sources by which it is illuminated. If the appearance of two objects is never identical for any pose or lighting conditions, then–in theory–the objects can always be distinguished or recognized. The question arises: What is the set of images of an object under all lighting conditions and pose? In this paper, we consider only the set of images of an object under variable illumination, including multiple, extended light sources and shadows. We prove that the set of n-pixel images of a convex object with a Lambertian reflectance function, illuminated by an arbitrary number of point light sources at infinity, forms a convex polyhedral cone in IRⁿ and that the dimension of this illumination cone equals the number of distinct surface normals. Furthermore, the illumination cone can be constructed from as few as three images. In addition, the set of n-pixel images of an object of any shape and with a more general reflectance function, seen under all possible illumination conditions, still forms a convex cone in IRⁿ. Extensions of these results to color images are presented. These results immediately suggest certain approaches to object recognition. Throughout, we present results demonstrating the illumination cone representation.

     

Implementing Fault-Tolerant Distributed Objects

This paper describes a technique for implementing k-resilient objects–distributed objects that remain available, and whose operations are guaranteed to progress to completion, despite up to k site failures. The implementation is derived from the object specification automatically, and does not require any information beyond what would be required for a nonresilient nondistributed implementation. It is therefore unnecessary for an applications programmer to have knowledge of the complex protocols nonnally employed to implement fault-tolerant objects. Our technique is used in ISIS, a system being developed at Cornell to support resilient objects.     

The Amulet environment: new models for effective user interfacesoftware development

The Amulet user interface development environment makes it easier for programmers to create highly interactive, graphical user interface software for Unix, Windows and the Macintosh. Amulet uses new models for objects, constraints, animation, input, output, commands, and undo. The object system is a prototype instance model in which there is no distinction between classes and instances or between methods and data. The constraint system allows any value of any object to be computed by arbitrary code and supports multiple constraint solvers. Animations can be attached to existing objects with a single line of code. Input from the user is handled by “interactor” objects which support reuse of behavior objects. The output model provides a declarative definition of the graphics and supports automatic refresh. Command objects encapsulate all of the information needed about operations, including support for various ways to undo them. A key feature of the Amulet design is that all graphical objects and behaviors of those objects are explicitly represented at run time, so the system can provide a number of high level built-in functions, including automatic display and editing of objects, and external analysis and control of interfaces. Amulet integrates these capabilities in a flexible and effective manner     

基于序列轮廓线的凸面目标全自动重构方法

凸面目标在成像时会表现尺寸较小、纹理稀疏或缺乏、透光、反光等特点.在对其进行三维重构时,传统的立体视觉匹配、主动视觉扫描(激光或结构光)等重构方法无法提供良好的解决方案.针对此类目标的重构难题,本文提出一种基于序列轮廓线的全自动重构方法.该方法首先采集目标的序列轮廓影像,然后提取高精度的轮廓线,再利用多个视角的轮廓线对初始外包体进行空间切割得到目标的初始三维模型,接着根据角度和面积约束对初始三维模型中的面进行合并,最后利用合并后的面重新对外包体进行精细切割得到目标的精确三维刻面模型.通过对凸面目标(注射器针头,直径约为3mm)的重构实验证明,利用本文的方法重构得到的模型角度误差小于0.7,执行时间小于15s,重构过程无需人工干预,能有效解决凸面目标的三维重构及视觉测量难题.     

基于线性规划的碰撞检测算法研究

介绍了虚拟环境中一种基于凸多面体面信息对偶线性规划模型(DualModel)的快速旋转和移动物体之间干涉碰撞实时检测方法。该文详细介绍了建模过程和求解步骤,物体由构成凸多面体的三角形面信息表示,而物体的运动由一组虚拟现实环境中的全局移动和旋转矩阵表示。这种数学编程方法具有数据结构简单、算法可靠和速度快等优点,同时能够很好地解决高速(运动帧)碰撞的问题。这一方法通过使用主-对偶(primal-dual)内点方法来解线性规划方程,具有很好的效果,能够检测多物体对之间的碰撞。实验结果表明,基于数学编程的方法相对两种著名的工具包I-COLLIDE和SOLID,具有速度快和稳定可靠的优点,而I-COLLIDE和SOLID工具包基于两种著名的算法:LinCanny(LC)最近特征算法和GJK算法(EnhancedGilbertJohnsonandKeethialgorithm)。     

Reflective workpiece detection and localization for flexible robotic cells

A smart vision system for industrial robotic cells is presented. It can recognize and localize a reflective workpiece, and allows for automatic adjustments of the robot program. The purpose of the study is to improve industrial robots awareness of the environment and to increase adaptability of the manufacturing processes where full control over environment is not achievable. This approach is particularly relevant to small batch robotic production, often suffering from only partial control of the process parameters, such as the order of jobs, workpiece position, or illumination conditions.A distinguishing aspect of the study is detection of workpieces made of diverse materials, including shiny metals. Reflective surfaces are common in the industrial manufacturing, but are rarely considered in the research on object recognition because they hinder many of the object recognition algorithms. The proposed solution has been qualified and tested on a selected benchmark in a realistic workshop environment with artificial light conditions. The training of the object recognition software is an automatic process and can be executed by non-expert industrial users to allow for recognition of different types of objects.     

A Robust Illumination Estimate for Chromatic Adaptation in Rendered Images

We propose a method that improves automatic colour correction operations for rendered images. In particular, we propose a robust technique for estimating the visible and pertinent illumination in a given scene. We do this at very low computational cost by mostly re-using information that is already being computed during the image synthesis process. Conventional illuminant estimations either operate only on 2D image data, or, if they do go beyond pure image analysis, only use information on the luminaires found in the scene. The latter is usually done with little or no regard for how the light sources actually affect the part of the scene that is being viewed. Our technique goes beyond that, and also takes object reflectance into account, as well as the incident light that is actually responsible for the colour of the objects that one sees. It is therefore able to cope with difficult cases, such as scenes with mixed illuminants, complex scenes with many light sources of varying colour, or strongly coloured indirect illumination.     

Application of redundant computation in program debugging

Programmers spend most of their time and resources in localizing program defects. On the other hand, they commit many errors by manipulating dynamic data improperly, which may produce dynamic memory problems, such as dangling pointer, memory leaks, and inaccessible objects. Dangling pointers can occur when a function returns a pointer to an automatic variable, or when trying to access a deleted object. Inaccessible objects occur when a pointer is assigned to point to another object, leaving the original object inaccessible, either by using the new operator or regular assignment operator. Memory leaks occur when a dynamic data is allocated but never de-allocated. The existence of such dynamic memory problems causes the programs to behave incorrectly. Improper usage of dynamic data is a common defect that is easy to commit, but is difficult to diagnose and discover. In this paper, we propose a dynamic approach that detects different types of program defects including those that occur as a result of misusing the dynamic data in computer programs. Our approach uses the notion of redundant computation to identify the suspicious locations in the program that may contain defects. Redundant computation is an execution of a program statement(s) that does not contribute to the program output. The notion of redundant computation is introduced as a potential indicator of defects in programs. We investigate the application of redundant computation in debugging programs. The detection of redundant computation indicates deficiency that may represent a bug in the program. The results of the experiment show that, the redundant computation detection can help the debuggers to localize the source(s) of the program defects.     

On planar path transformation

A flip or edge-replacement is considered as a transformation by which one edge e of a geometric object is removed and an edge f (f≠e) is inserted such that the resulting object belongs to the same class as the original object. Here, we consider Hamiltonian planar paths as geometric objects. A technique is presented for transforming a given planar path into another one for a set S of n points in convex position in the plane. Under these conditions, we show that any planar path can be transformed into another planar path by at most 2n−5 flips. For the case when the points are in general position we provide experimental results regarding transformability of any planar path into another. We show that for n?8 points in general position any two paths can be transformed into each other. For n points in convex position we show that there are n²n−2 directed Hamiltonian planar paths. An algorithm is presented which uses flips of size 1 and flips of size 2 to generate all such paths with O(n) time between the generation of two successive paths.     

A new approach for the voxelization of volumetric CSG graphs

This paper presents a new approach for the voxelization of volumetric scene graphs. The algorithm generates slices of each primitive intended to be voxelized using an FPGA based pixel processor. The Blist representation is used for the volume scene tree which reduces storage requirement for each voxel to the log(H+1) bits. The most important advantage of this voxelization algorithm is that any volume scene tree expression can be evaluated without using any computation or stack. Also the algorithm is not object specific, i.e. the same algorithm can be used for the voxelization of different types of objects (convex and concave objects, polygons, lines and surfaces).     

最优化凸分组在目标检测中的应用研究

针对不同场景下静态图像中单目标的检测问题,结合自然界各个目标特有的凸属性特点,提出了一种基于最优化凸分组的目标检测方法。比较系统地论述了最优化凸分组的基本原理,介绍了详细的实现过程,主要包括Canny边缘检测参数的设置、基于边缘点的线段拟合、凸分组中凸多边形的构造以及最优化凸多边形的判定。实验结果表明,该方法对任意场景下的单目标检出率和检测准确性良好,结合目标凸属性的最优化判定方式具有检出速度快,且不受机器学习中的样本数据影响的特点,具有很好的普遍适应性。