Polygonal Objects Research Articles

Energy-Bounded Caging: Formal Definition and 2-D Energy Lower Bound Algorithm Based on Weighted Alpha Shapes

Caging grasps are valuable as they can be robust to bounded variations in object shape and pose, do not depend on friction, and enable transport of an object without full immobilization. Complete caging of an object is useful but may not be necessary in cases where forces such as gravity are present. This letter extends caging theory by defining energy-bounded cages with respect to an energy field such as gravity. This letter also introduces energy-bounded-cage-analysis-2-D (EBCA-2-D), a sampling-based algorithm for planar analysis that takes as input an energy function over poses, a polygonal object, and a configuration of rigid fixed polygonal obstacles, e.g., a gripper, and returns a lower bound on the minimum escape energy. In the special case when the object is completely caged, our approach is independent of the energy and can provably verify the cage. EBCA-2-D builds on recent results in collision detection and the computational geometric theory of weighted $\alpha$ -shapes and runs in $O(s^2 + s n^2)$ time where $s$ is the number of samples, $n$ is the total number of object and obstacle vertices, and typically $n \textless\textless s$ . We implemented EBCA-2-D and evaluated it with nine parallel-jaw gripper configurations and four nonconvex obstacle configurations across six nonconvex polygonal objects. We found that the lower bounds returned by EBCA-2-D are consistent with intuition, and we verified the algorithm experimentally with Box2-D simulations and RRT* motion planning experiments that were unable to find escape paths with lower energy. EBCA-2-D required an average of 3 min per problem on a single-core processor but has potential to be parallelized in a cloud-based implementation. Additional proofs, data, and code are available at: http://berkeleyautomation.github.io/caging/.

Space-Time Topological Graphs

GIScience 2016 Short Paper Proceedings Space-Time Topological Graphs C. Robertson 1 Wilfrid Laurier University, 75 University Ave, Waterloo, ON Email: crobertson@wlu.ca Abstract The integration of space and time in geospatial analyses is an active research area. While methods for characterizing sequences of spatial point objects over time have evolved greatly over recent years, the treatment of space-time change in complex geographic objects such as linear features and polygons has seen much less attention. In this paper we consider the directed graph as a representation for temporal change in spatial objects, where edges are formed by spatial relationships. With this representation, the large foundation of graph- theoretic metrics and algorithms can be used for the analysis of space-time change in geographic objects. We present preliminary findings using several exemplar datasets: range expansion of polygons representing animal home ranges, the spatial path of Hurricane Katrina, and a forest insect outbreak. In particular, we investigate the dynamics of space-time change in these datasets using well-known metrics for characterizing graph structures. 1. Introduction Understanding space-time change continues to be a challenging and increasingly required task for geospatial analysis, as more spatial datasets are evolving into long-term records of spatial and temporal change (e.g, satellite archives, long-term radio collar studies). However, models of space-time change remain to be fulll developed. Stell et al. (2011) introduced a bigraph representation of space-time change, whereby objects were represented as nodes at discrete time points, and linked through relations. As well, Del Mondo et al. 2012 further developed this model with an explicit spatiotemporal graph representation, distinguishing between filial relations (based on explicit identity) and purely topological relations (derived from spatial relationships). We build on these ideas from the perspective of space-time analysis in order to analyze spatial changes in polygon objects over time. We use several space-time polygon datasets in order to explore a how space-time topological graphs can be used as a representation for spatial-temporal analysis generally. 1.1 Polygon models of space-time change Sadahiro and Umemura (2001) introduced a framework for the analysis of spatio-temporal polygon distributions based on events derived from spatial overlap relations in neighbouring time-steps. The scope of events was extended in Robertson et al. (2007) to include proximity- based spatial relations, describing various types of movement occurring over the change interval, known as spatial-temporal analysis of moving polygons (STAMP). The STAMP framework is temporally discrete, such that an appropriate temporal grain is required a priori in order to represent change. Metrics associated with space-time change include counts of event types, area change, directional change, all of which can be accumulated along paths of the graph representing continuous spatial relationships over time. In Sadahiro (2001) the graph representation of polygon change events was introduced. In this paper we build on this framework order to integrate existing graph metrics into the spatial-temporal analysis of polygon distributions.

Symmetric caging formation for convex polygonal object transportation by multiple mobile robots based on fuzzy sliding mode control

In this paper, the problem of object caging and transporting is considered for multiple mobile robots. With the consideration of minimizing the number of robots and decreasing the rotation of the object, the proper points are calculated and assigned to the multiple mobile robots to allow them to form a symmetric caging formation. The caging formation guarantees that all of the Euclidean distances between any two adjacent robots are smaller than the minimal width of the polygonal object so that the object cannot escape. In order to avoid collision among robots, the parameter of the robots radius is utilized to design the caging formation, and the A⁎ algorithm is used so that mobile robots can move to the proper points. In order to avoid obstacles, the robots and the object are regarded as a rigid body to apply artificial potential field method. The fuzzy sliding mode control method is applied for tracking control of the nonholonomic mobile robots. Finally, the simulation and experimental results show that multiple mobile robots are able to cage and transport the polygonal object to the goal position, avoiding obstacles.

Two-Finger Caging of Polygonal Objects Using Contact Space Search

Multifinger caging offers a rigorous and robust object grasping approach. Focusing on two-finger caging, this paper describes an algorithm for finding all two-finger cage formations of planar polygonal objects based on contact-space formulation. The paper shows that two-finger cages have several useful properties in contact space. First, the critical points of the cage representation in the hand's configuration space appear as critical points of the interfinger distance function in contact space. Second, these critical points can be graphically characterized directly on the object's boundary. Third, contact space admits a natural rectangular decomposition such that all critical points lie on the rectangle boundaries, and the sublevel sets of contact space and free space are topologically equivalent. These properties lead to a caging graph that can be readily constructed in contact space. Starting from a desired immobilizing grasp of a polygonal object, the caging graph is searched for the minimal, intermediate, and maximal caging regions surrounding the immobilizing grasp. An example constructed from real-world data illustrates and validates the method.

High-quality slab-based intermixing method for fusion rendering of multiple medical objects

The visualization of multiple 3D objects has been increasingly required for recent applications in medical fields. Due to the heterogeneity in data representation or data configuration, it is difficult to efficiently render multiple medical objects in high quality. In this paper, we present a novel intermixing scheme for fusion rendering of multiple medical objects while preserving the real-time performance. First, we present an in-slab visibility interpolation method for the representation of subdivided slabs. Second, we introduce virtual zSlab, which extends an infinitely thin boundary (such as polygonal objects) into a slab with a finite thickness. Finally, based on virtual zSlab and in-slab visibility interpolation, we propose a slab-based visibility intermixing method with the newly proposed rendering pipeline. Experimental results demonstrate that the proposed method delivers more effective multiple-object renderings in terms of rendering quality, compared to conventional approaches. And proposed intermixing scheme provides high-quality intermixing results for the visualization of intersecting and overlapping surfaces by resolving aliasing and z-fighting problems. Moreover, two case studies are presented that apply the proposed method to the real clinical applications. These case studies manifest that the proposed method has the outstanding advantages of the rendering independency and reusability.

A QUALITY ASSESSMENT METHOD FOR 3D ROAD POLYGON OBJECTS

Abstract. With the development of the economy, the fast and accurate extraction of the city road is significant for GIS data collection and update, remote sensing images interpretation, mapping and spatial database updating etc. 3D GIS has attracted more and more attentions from academics, industries and governments with the increase of requirements for interoperability and integration of different sources of data. The quality of 3D geographic objects is very important for spatial analysis and decision-making. This paper presents a method for the quality assessment of the 3D road polygon objects which is created by integrating 2D Road Polygon data with LiDAR point cloud and other height information such as Spot Height data in Hong Kong Island. The quality of the created 3D road polygon data set is evaluated by the vertical accuracy, geometric and attribute accuracy, connectivity error, undulation error and completeness error and the final results are presented.

GPU-based smooth free-form deformation with sharp feature awareness

In an accurate free-form deformation of a polygonal object, only the linear geometry, e.g., triangles or planar polygons, is deformed as triangular Bézier patches or trimmed tensor product Bézier patches; the related normal field is not considered. Thus, the geometry appearance and shading of the deformed object are typically not smooth. In this paper, both the linear geometry and normal of a polygonal object are simultaneously considered in the framework of accurate free-form deformation. First, each triangle and its normal field are deformed as two cubic triangular Bézier patches. Then, the curved geometry corresponding to the deformed triangles is locally adjusted to tone the smoothness of the geometry appearance according to the deformed normal field. The deformed normal field is adjusted accordingly. As a result, a smooth free-form deformation with visually plausible smooth geometry and shading is obtained. Furthermore, the sharp features in the polygonal object can be preserved. Because the curved geometry and normal field adjustments are local operations, all of the above computations can be performed in parallel on a GPU. The experimental results show that the method can deform a complex polygonal object as a smooth object in real time while preserving sharp features.

파일 및 병렬 처리를 이용한 표면 객체의 복셀화 방안

This paper suggests an efficient method for making the high resolution volexlized model from a polygonal surface object. A distinctive strength of the method is that a surface model, however complex one, can be transformed and formed an absolute voxelized solid model in a various resolution. It caused by producing a voxel by integrating the informations for the candidated voxels separately detected in each 3D-axial direction. This method reduces memory complexity by storing the information of voxels that is produced during the 2-phase volxelization(surface and inner voxelization) of a surface object in a binary file. For the computational efficiency, a parallel process using multi-threads is applied in the process of the inner voxelization, it also takes advantage of time complexity.

THE POSSIBILITIES TO SUPPORT ZB GIS DATABASE UPDATE USING OBJECT-BASED IMAGE ANALYSIS IN ECOGNITION DEVELOPER SOFTWARE

The process of updating a spatial database is a necessary part of database management in order to keep the stored information of an acceptable quality. The first step of database update requires change detection. Many methods have been suggested to detect changes, mostly pixel-based. Recently, with the spread of very high resolution images and object-based image analysis, object-based methods were developed, too. This article presents object-based change detection method for update of the vector database ZB GIS, that is a geometric base of the Slovak National infrastructure of spatial information, using orthophoto of the area of interest. The method stages include the following: segmentation of orthophoto using the geometry of database objects and further according to spectral and spatial information, classification according to ZB GISR, defining reclassification rules between two classes. The proposed method was tested in two localities – Malženice (agricultural landscape) and Chopok-Jasna (mountainous landscape) reaching the overall accuracy of classification 87.12% and 84.55%, respectively. The main limitation of the method is that it can be applied only for polygonal objects.

M:N object matching between image and map object data sets by means of latent semantic analysis

In this article, we propose a method to find corresponding object-set pairs between image and map polygon object data sets by means of latent semantic analysis. Latent semantic analysis assigns each polygon object of both data sets to feature vectors in a continuous geometric space in which the similarities between the vectors are proportional to the priorities to constitute a corresponding object-set pair. Thus, object clusters can be obtained by applying an agglomerative hierarchical clustering to the feature vectors. These object clusters are separated into object-set pairs according to the data sets to which the objects belong and are evaluated with a geometric matching criterion to find corresponding object-set pairs. We applied the proposed method to the segmentation result of a composite image with six normalized difference vegetation index (NDVI) images and a forest inventory map. The proposed method was compared to a graph-embedding-based method. The results showed that the proposed method found more corresponding object-set pairs with a similar accuracy in terms of shape similarities and shared information of found pairs.

Microscopic measurements of planar viscoelastic body eccentric impacts on a convex corner

This paper presents the effects of the target edge shape on eccentric impact motions, which were experimentally investigated by concurrently measuring the microscopic deformation of the target edge around a contact point and the global trajectory. This study is important for understanding the impact motions that occur between viscoelastic deformable polygonal objects with friction. The materials used in this experiment were four types of resin and one metal; four convex shapes and one circular shape were used for the impacted target plate. Interestingly, anomalous trajectories of the impact plate that varied with the target edge shape were found beyond the regime of rigid body dynamics, and were strongly dependent on the tangential deformation of the edge. In addition, it was found that the tangential deformation amount had a correlation with the bounce-off angle of the impact body for all materials used. That is, the target edge had a weaker tangential stiffness with sharpening of the edge shape, and thus, remarkably, absorbed the tangential impact energy as strain energy, due to a tangential deformation of the edge. Consequently, the bounce-off angle of the elastic body became smaller than that generally expected from rigid body dynamics, and sometimes even became negative because the direction of the contact force is significantly changed with increase in the tangential deformation of the edge.

Touring a sequence of disjoint polygons: Complexity and extension

In the Touring Polygons Problem (TPP) there is a start point s, a sequence of simple polygons P=(P1,…,Pk) and a target point t in the plane. The goal is to obtain a path of minimum possible length that starts from s, visits in order each of the polygons in P and ends at t. This problem was introduced by Dror, Efrat, Lubiw and Mitchell in STOC '03. They proposed a polynomial time algorithm for the problem when the polygons in P are convex and proved its NP-hardness for intersecting and non-convex polygons. They asked as an open problem whether TPP is NP-hard when the polygons are pairwise disjoint. In this paper, we prove that TPP is also NP-hard when the polygons are pairwise disjoint in any Lp norm even if each polygon consists of at most two line segments. This result complements approximation results recently proposed for the touring disjoint polygons problem. As a similar problem, we study the touring objects problem (TOP) and present an efficient polynomial time algorithm for it. This problem is similar to TPP but instead of polygons, we have solid polygonal objects that the tour cannot pass through.

Hough-transform based algorithm for the automatic invariant recognition of rectangular chocolates. Detection of defective pieces.

La Transformada de Hough (TH) ha sido usada para crear un algoritmo de reconocimiento invariante (rotación, traslación y cambio de escala) de objetos poligonales. En esta investigación, el sistema desarrollado ha sido exitosamente aplicado al reconocimiento automático invariante de chocolates rectangulares, incluyendo la identificación de piezas falladas. Como la ejecución total del sistema resultante es totalmente autónoma, los resultados pueden ser aplicados al control automático de calidad en aplicaciones industriales.

Variability of operator performance in remote-sensing image interpretation: the importance of human and external factors

This study tackles a common, yet underrated problem in remote-sensing image analysis: the fact that human interpretation is highly variable among different operators. Despite current technological advancements, human perception and interpretation are still vital components of the map-making process. Consequently, human errors can considerably bias both mapping and modelling results. In our study, we present a web-based tool to quantify operator variability and to identify the human and external factors affecting this variability. Human operators were given a series of images and were asked to hand-digitize different point, line, and polygon objects. The quantification of performance variability was achieved using both thematic and positional accuracy measures. Subsequently, a series of questions related to demographics, experience, and personality were asked, and the answers were also quantified. Correlation and regression analysis was then used to explain the variability in operator performance. From our study, we conclude that: (1) humans were seldom perfect in visual interpretation; (2) some geographic objects were more complex to accurately digitize than others; (3) there was a high degree of variability among image interpreters when hand-digitizing the same objects; and (4) operator performance was mainly determined by demographic, non-cognitive, and cognitive personality factors, whereas external and technical factors influenced operator performance to a lesser extent. Finally, the results also indicated a gradual decline in performance over time, mimicking classical mental fatigue effects.

Natural Convection in a Differentially Heated Square Enclosure with a Solid Polygon

The aim of the present numerical study is to analyze the conjugate natural convection heat transfer in a differentially heated square enclosure containing a conductive polygon object. The left wall is heated and the right wall is cooled, while the horizontal walls are kept adiabatic. The COMSOL Multiphysics software is applied to solve the dimensionless governing equations. The governing parameters considered are the polygon type, 3 ≤ N ≤ ∞, the horizontal position, 0.25 ≤ X 0 ≤ 0.75, the polygon size, 0 ≤ A ≤ π/16, the thermal conductivity ratio, 0.1 ≤ K r ≤ 10.0, and the Rayleigh number, 103 ≤ Ra ≤ 106. The critical size of the solid polygon was found exists at low conductivities. The heat transfer rate increases with the increase of the size of the solid polygon, until it reaches its maximum value. Here, the size of the solid polygon is reaches its critical value. Further, beyond this critical size of the solid polygon, will decrease the heat transfer rate.

Optimal motion planning of juggling by 3-DOF manipulators using adaptive PSO algorithm

SUMMARYThree-DOF manipulators were employed for juggling of polygonal objects in order to have full control over object's configuration. Dynamic grasp condition is obtained for the instances that the manipulators carry the object on their palms. Manipulation problem is modeled as a nonlinear optimal control problem. In this optimal control problem, time of free flight is used as a free parameter to determine throw and catch times. Cost function is selected to get maximum covered horizontal distance using minimum energy. By selecting third-order polynomials for joint motions, the problem is changed to a constrained parameter selection problem. Adaptive particle swarm optimization method is consequently employed to solve the optimization problem. Effectiveness of the optimization algorithm is verified by a set of simulations in MSC. ADAMS.

Information-technologycal support of post launch calibration of optoelectronic monitoring sensors of “Sich” space system

We consider the study results directed to creation in Ukraine of postlaunch metrological assurance of remote sensing systems based on developed evidence-based techniques, deployed land-based infrastructure of control and calibration polygon (CCP) systems with the test objects (TO) and measuring instruments and created software and hardware systems. The CCP infrastructure in the area of National Space Facilities Control and Test Center (NSFCTC) (Yevpatoriya-19) is ground, using as the standard template for describing the CCP approved by the Working Group on Calibration and Validation of the CEOS Committee. Based on the results of experiments to determine the spectral reflectance characteristics of the selected TO on ground-based measurements which are synchronous with satellite imagery of the space system (SS) “Sich-2”, GIS database is created. It contains the vector layers of polygonal natural and man-made objects of NSFCTC, layers of the spectral characteristics measurement points, satellite images of the SS “Quick Bird-2” and “Sich-2”, the digital terrain model of CCP. Such devices for ground-based measurements are analyzed, which must be equipped the test plots of polygon for control and calibration activities: 1) as the number of available to researchers: the digital weather station, spectrometers ASP-100F, ASD FieldSpec 3FR, equipment for precision measurements of the geodetic reference mark coordinates, 2) and the instruments used at the polygons of the LANDNET Sites System of CEOS Committee: CIMEL sun photometers in the AERONET CIMEL network, portable sun photometers MICROTOPS II, gonio radiometric spectrometer systems.

Quantitative Models for Computing Distance and Directions: A Raster-Based Approach

Modeling Distance and Direction Relationships (DDR) is a key issue in spatial analysis and spatial reasoning. Various fields such as geology, hydrology, ecology, etc. apply DDR models to help digging out valuable patterns hidden in geoscientific dataset. This paper proposed two quantitative models through a raster-based approach for computing Euclidean distance and cardinal direction relationships, respectively, between a pair of spatial objects in a two-dimensional geographical space. The corresponding algorithms were designed and implemented. This new raster-based modeling can work universally on all types of spatial objects (point, line, polygon, or compound objects) and quantify DDR more accurately due to its sensitivity to object shapes. The usefulness of the modeling was demonstrated by various applications.

필지 객체의 형상 정합을 이용한 건물 설계도면의 좌표 등록

This study proposed a map registration method of a building construction plan drawing with shape matching of cadastral parcel polygon. In general, the drawing contains information about a building boundary and a cadastral parcel boundary. The shape of this cadastral parcel boundary should be same as that of the corresponding parcel polygon object in the KLIS continuous cadastral map. Thus, shape matching between two parcel boundary polygons from the drawing and cadastral map could present transformation parameters. Translation and scaling amounts could be obtained by difference of centroid coordinates and area ratio of the polygons, respectively. Rotation amount could be obtained by the rotation that presents the minimum Turning function dissimilarity of the polygons. The proposed method was applied for building construction plan drawings in eAIS for an urban area in Suwon. To assess positional accuracy of map registration, building polygons in registered drawings and aerial photos were compared. According to the accuracy of the cadastral map which is the reference dataset of the proposed method, the RMSE of corresponding buildings` corners was 0.95m and 2.37m in new and old urban areas, respectively.

Line segment confidence region-based string matching method for map conflation

In this paper, a method to detect corresponding point pairs between polygon object pairs with a string matching method based on a confidence region model of a line segment is proposed. The optimal point edit sequence to convert the contour of a target object into that of a reference object was found by the string matching method which minimizes its total error cost, and the corresponding point pairs were derived from the edit sequence. Because a significant amount of apparent positional discrepancies between corresponding objects are caused by spatial uncertainty and their confidence region models of line segments are therefore used in the above matching process, the proposed method obtained a high F-measure for finding matching pairs. We applied this method for built-up area polygon objects in a cadastral map and a topographical map. Regardless of their different mapping and representation rules and spatial uncertainties, the proposed method with a confidence level at 0.95 showed a matching result with an F-measure of 0.894.