Polyhedral objects identification through the orthographic projection views generation

This paper presents a new method to automatic recognition of polyhedra. Given images taken from different viewpoints of designated polyhedra, algorithms are developed to interpret them as the same object. Based on the heuristic inference of the polyhedral scene regularities and the gradient space analysis, this method will restore the 3-D information of the polyhedra. The 3-D data is used for the generation of the orthographic projection views of the observed object which consist of the top view, the front view, and the side view.     

Providing multiple views for objects

The need for multiple views of an object is often encountered in software practice. This paper presents our experience in addressing this need under a software architecture known as the law‐governed architecture. We introduce the notion of a surrogate object which allows an object to appear different and behave differently when used from different parts of a system. This concept requires some minor modifications to the classical inheritance‐based object‐oriented systems, mostly involving a judicious use of delegation. A concrete implementation of surrogates under the law‐governed architecture is described and some applications of surrogates are briefly discussed. Copyright © 2000 John Wiley & Sons, Ltd.     

Estimation of three-dimensional objects from orthographic views with inconsistencies

Many algorithms to construct 3-D solid objects from orthographic views assume the bottom-up approach. This paper describes a method for identifying conflictions found in inconsistent views which improbably present complete objects and estimating solid objects. The sources of inconsistencies are extra segments, missing segments and incorrect classifications of line types (visible lines or hidden lines). In order to supply candidates for missing segments, probable segments are generated not from three views but from two views. The signs appearing in each step of the bottom-up algorithm are examined, and then the heuristic method for selecting more probable segments is developed. The estimation of solid objects and identification of incoherences are useful, for example, to detect improper input of three views and incorrect recognition of engineering drawings.     

Construction of 3D solid objects from orthographic views

An algorithm to generate three-dimensional solid objects, made up of planar surfaces, from the given three conventional engineering orthographic views is presented in this paper. Consisting of six major steps, the algorithm has been programmed in C on IRIS 1400 graphics workstation. The algorithm generates all possible solutions. The infinite space has been divided into finite subspaces by making use of the surface normals and the direction of travel of the edges that connect the faces. Classification of the probable 3D subobjects into the certain and uncertain ones has proved to be very useful in reducing the time taken by the algorithm. Several illustrative examples, simple as well as complex giving single and multiple solutions, are included.     

Learning to generate novel views of objects for class recognition

Multi-view object class recognition can be achieved using existing approaches for single-view object class recognition, by treating different views as entirely independent classes. This strategy requires a large amount of training data for many viewpoints, which can be costly to obtain. We describe a method for constructing a weak three-dimensional model from as few as two views of an object of the target class, and using that model to transform images of objects from one view to several other views, effectively multiplying their value for class recognition. Our approach can be coupled with any 2D image-based recognition system. We show that automatically transformed images dramatically decrease the data requirements for multi-view object class recognition.     

应用多个正交视角轮流逼近3维目标的坐标

为实现目标的快速、精确3维定位和跟踪,提出一种正交摄像机视频定位系统及其坐标轮流逼近的迭代定位算法。系统中平面摄像机光轴按照正交方式布置,拍摄方向均指向原点。不同于现有的大部分计算机视觉方法,本算法中没有影响定位效率和精度问题的图像配准操作。证明了迭代算法的收敛性。数值验证和实际试验表明,本算法计算简单、误差稳定性好,收敛快,因此具有良好的应用潜力。     

New methods for matching 3-d objects with single perspective views

In this paper we analyze the ability of a computer vision system to derive properties of the three-dimensional (3-D) physical world from viewing two-dimensional (2-D) images. We present a new approach which consists of a model-based interpretation of a single perspective image. Image linear features and linear feature sets are backprojected onto the 3-D space and geometric models are then used for selecting possible solutions. The paper treats two situations: 1) interpretation of scenes resulting from a simple geometric structure (orthogonality) in which case we seek to determine the orientation of this structure relatively to the viewer (three rotations) and 2) recognition of moderately complex objects whose shapes (geometrical and topological properties) are provided in advance. The recognition technique is limited to objects containing, among others, straight edges and planar faces. In the first case the computation can be carried out by a parallel algorithm which selects the solution that has received the largest number of votes (accumulation space). In the second case an object is uniquely assigned to a set of image features through a search strategy. As a by-product, the spatial position and orientation (six degrees of freedom) of each recognized object is determined as well. The method is valid over a wide range of perspective images and it does not require perfect low-level image segmentation. It has been successfully implemented for recognizing a class of industrial parts.     

Constructing a wire-frame from views on arbitrary view planes for objects with conic sections inclined to all view planes

A new and efficient approach to construct a 3D wire-frame of an object from its orthographic projections is described. The input projections can be two or more and can include regular and complete auxiliary views. Each view may contain linear, circular and other conic sections. The output is a 3D wire-frame that is consistent with the input views.The approach can handle auxiliary views containing curved edges. This generality derives from a new technique to construct 3D vertices from the input 2D vertices (as opposed to matching coordinates that is prevalent in current art). 3D vertices are constructed by projecting the 2D vertices in a pair of views on the common line of the two views. The construction of 3D edges also does not require the addition of silhouette and tangential vertices and subsequently splitting edges in the views. The concepts of complete edges and n-tuples are introduced to obviate this need. Entities corresponding to the 3D edge in each view are first identified and the 3D edges are then constructed from the information available with the matching 2D edges. This allows the algorithm to handle conic sections that are not parallel to any of the viewing directions. The localization of effort in constructing 3D edges is the source of efficiency of the construction algorithm as it does not process all potential 3D edges.Working of the algorithm on typical drawings is illustrated.     

VinEd — Asystem for programmanipulation through user-definable simultaneous views

Programmers’ mental representations of programs do not obey the order and immediate content of program texts. Multiple visible representations, or views, of programs help programmers to construct mental representations needed in, e.g., maintenance tasks. We have implemented VinEd, a language-independent editor framework that supports an unlimited number of user-definable and editable views. Views are defined by transformation programs that construct views from the original representation. VinEd extends the notion of views to any activity that can be based on the original program, e.g., program compilation. Thus VinEd can be extended to include a complete set of programming tools.     

Efficient image retrieval through vantage objects

We describe a new indexing structure for general image retrieval that relies solely on a distance function giving the similarity between two images. For each image object in the database, its distance to a set of m predetermined vantage objects is calculated; the m-vector of these distances specifies a point in the m-dimensional vantage space. The database objects that are similar (in terms of the distance function) to a given query object can be determined by means of an efficient nearest-neighbor search on these points. We demonstrate the viability of our approach through experimental results obtained with two image databases, one consisting of about 5200 raster images of stamps, the other containing about 72,000 hieroglyphic polylines.     

Faster joins, self-joins and multi-way joins using join indices

We propose a new algorithm, called Stripe-join, for performing a join given a join index. Stripe-join is inspired by an algorithm called ‘Jive-join’ developed by Li and Ross. Stripe-join makes a single sequential pass through each input relation, in addition to one pass through the join index and two passes through a set of temporary files that contain tuple identifiers but no input tuples. Stripe-join performs this efficiently even when the input relations are much larger than main memory, as long as the number of blocks in main memory is of the order of the square root of the number of blocks in the participating relations. Stripe-join is particularly efficient for self-joins. To our knowledge, Stripe-join is the first algorithm that, given a join index and a relation significantly larger than main memory, can perform a self-join with just a single pass over the input relation and without storing input tuples in intermediate files. Almost all the I/O is sequential, thus minimizing the impact of seek and rotational latency. The algorithm is resistant to data skew. It can also join multiple relations while still making only a single pass over each input relation. Using a detailed cost model, Stripe-join is analyzed and compared with competing algorithms. For large input relations, Stripe-join performs significantly better than Valduriez's algorithm and hash join algorithms. We demonstrate circumstances under which Stripe-join performs significantly better than Jive-join. Unlike Jive-join, Stripe-join makes no assumptions about the order of the join index.     

利用XML视图更新关系数据库

XML已成为数据交换的一个重要介质,也被作为一个接口,即一个关系数据库的一个视图。此前,关于利用XML视图查询关系数据库(例如Silkroute)的问题有人已经做过深入探讨。对于关系数据库上XML视图的可更新性,首先考虑的是如何通过一个XML视图更新一个关系数据库的问题,把嵌套的关系代数作为一个关系数据库的XML视图,然后再考虑这个视图什么时候是可更新的问题。     

Formal anonymity models for efficient privacy-preserving joins

Organizations, such as federally-funded medical research centers, must share de-identified data on their consumers to publicly accessible repositories to adhere to regulatory requirements. Many repositories are managed by third-parties and it is often unknown if records received from disparate organizations correspond to the same individual. Failure to resolve this issue can lead to biased (e.g., double counting of identical records) and underpowered (e.g., unlinked records of different data types) investigations. In this paper, we present a secure multiparty computation protocol that enables record joins via consumers’ encrypted identifiers. Our solution is more practical than prior secure join models in that data holders need to interact with the third party one time per data submission. Though technically feasible, the speed of the basic protocol scales quadratically with the number of records. Thus, we introduce an extended version of our protocol in which data holders append k-anonymous features of their consumers to their encrypted submissions. These features facilitate a more efficient join computation, while providing a formal guarantee that each record is linkable to no less than k individuals in the union of all organizations’ consumers. Beyond a theoretical treatment of the problem, we provide an extensive experimental investigation with data derived from the US Census to illustrate the significant gains in efficiency such an approach can achieve.     

Reconstruction of three-dimensional objects through matching oftheir parts

The problem of re-assembling an object from its parts or fragments has never been addressed with a unified computational approach, which depends on the pure geometric form of the parts and not on application-specific features. We propose a method for the automatic reconstruction of a model based on the geometry of its parts, which may be computer-generated models or range-scanned models. The matching process can benefit from any other external constraint imposed by the specific application     

A symmetric fragment and replicate algorithm for distributed joins

It is shown that the fragment and replicate (FR) distributed join algorithm is a special case of the symmetric fragment and replicate (SFR) algorithm, which improves the FR algorithm by reducing its communication. The SFR algorithm, like the FR algorithm, is applicable to N-way joins and nonequijoins and does tuple balancing automatically. The authors derive formulae that show how to minimize the communication in the SFR algorithm, discuss its performance on a parallel database prototype, and evaluate its practicality under various conditions. It is claimed that SFR improves the worst-case cost for a distributed join, but it will not displace specialized distributed join algorithms when the later are applicable     

Investigation of smoothness-increasing accuracy-conserving filters for improving streamline integration through discontinuous fields

Streamline integration of fields produced by computational fluid mechanics simulations is a commonly used tool for the investigation and analysis of fluid flow phenomena. Integration is often accomplished through the application of ordinary differential equation (ODE) integrators--integrators whose error characteristics are predicated on the smoothness of the field through which the streamline is being integrated--smoothness which is not available at the inter-element level of finite volume and finite element data. Adaptive error control techniques are often used to ameliorate the challenge posed by inter-element discontinuities. As the root of the difficulties is the discontinuous nature of the data, we present a complementary approach of applying smoothness-enhancing accuracy-conserving filters to the data prior to streamline integration. We investigate whether such an approach applied to uniform quadrilateral discontinuous Galerkin (high-order finite volume) data can be used to augment current adaptive error control approaches. We discuss and demonstrate through numerical example the computational trade-offs exhibited when one applies such a strategy.     

Execution trace analysis through massive sequence and circular bundle views

An important part of many software maintenance tasks is to gain a sufficient level of understanding of the system at hand. The use of dynamic information to aid in this software understanding process is a common practice nowadays. A major issue in this context is scalability: due to the vast amounts of information, it is a very difficult task to successfully navigate through the dynamic data contained in execution traces without getting lost.In this paper, we propose the use of two novel trace visualization techniques based on the massive sequence and circular bundle view, which both reflect a strong emphasis on scalability. These techniques have been implemented in a tool called Extravis. By means of distinct usage scenarios that were conducted on three different software systems, we show how our approach is applicable in three typical program comprehension tasks: trace exploration, feature location, and top-down analysis with domain knowledge.     

Supporting tailorable program visualisation through literate programming and fisheye views

This paper describes the ‘Jaba’ program editor and browser that allows users to tailor the level of abstraction at which they visualise, browse, edit and document object-oriented programs. Its design draws on concepts from literate programming, holophrasting displays, fisheye visualisation and hypertext to allow programmers to rapidly move between abstract and detailed views of Java classes. The paper focuses on the motivation for, and user interface issues surrounding, the integration of these facilities in Jaba. Limitations in the current tools and theories for programming support are identified, and modifications are proposed and demonstrated. Examples include overcoming the static post-hoc documentation support provided by Javadoc, and normalising Furnas's ‘degree of interest’ fisheye visualisation formula to avoid excessive suppression of program segments.     

Disassembly sequences for objects built from unit cubes

The geometrical problem of finding a possible disassembly sequence for an object is considered for a limited class of objects: those whose parts can be made from collections of unit cubes. For such objects, we consider motions of their component parts which are translations in one of three orthogonal directions.

A working program has been implemented in -11, which finds a disassembly sequence for an object defined by a 3D cube map. Each disassembly step may consist of either one or two linear motions of single parts. Removal of subassemblies consisting of more than one part is not considered.

To ensure properly the validity of a disassembly motion, both local and global geometric information must be considered. The local geometric feasibility of a motion relates to whether an infinitesimal motion can be made, and it is determined by the surface contacts (mates) between a part and other parts. The global geometric feasibility of a motion relates to whether a finite (or infinite) motion can be made in a particular direction. It depends not only on the relationship between the part to be moved and those that it touches, but also on its relationship with, potentially, all the other parts in the assembly. To determine the global geometric feasibility of a motion, the idea of coupling between two faces is introduced. Coupling is a directional quantity which gives the finite limit on the relative motion between two faces. By considering the coupling information for all the faces of a part, it is easy to determine the finite motions that are possible in any direction.