Modeling Of Complex Objects Research Articles

An object-oriented data model for complex objects in three-dimensional geographical information systems

Developing a three-dimensional (3D) data model for Geographic Information Systems (GIS) is an essential and complex issue. 3D modelling in GIS is becoming ever more important for the development of cyber cities and digital earth, which have recently become feasible. A competent 3D model forms an efficient foundation for 3D visualization, query and spatial analysis. As a development of the existing 3D models, this study proposes particular improvements in handling complex 3D objects. We present an object-oriented data model for handling complex 3D objects in GIS. First, the conceptual data model is developed based on the principle of object-oriented (OO) data modelling. This model is designed based on the following three basic geometric elements: node, segment and triangle. Accordingly, the abstract geometric objects are defined: including points, lines, surfaces and volumes. Second, the corresponding 3D logical model is designed based on the defined abstract objects and the relationships between them. Third, a formal representation of the 3D spatial objects is described in detail. Fourth, a prototype 3D GIS is developed based on the proposed 3D data model. Finally, we describe the results of an experimental study to reconstruct 3D objects using this 3D GIS and a comparison with the performance of other 3D data models. The proposed model is able to handle complex objects, such as complex buildings and TV towers, which is an essential functionality for building large-scale cyber cities, such as for Hong Kong. The proposed data model proves to be very efficient, particularly in visualization and rendering. The experimental results show which the data volume of the proposed model is compacted and the visualization speed for 3D objects is improved, compared with the existing models.

BSPro COM-Server—interoperability between software tools using industrial foundation classes

The continuing development of the Industry Foundation Classes (IFC) standard by the International Alliance for Interoperability (IAI) creates new possibilities for achieving interoperability for design software through the use of a common object model of the building and its open data transfer standard. Several architectural CAD tools are already IFC-compliant. However, in-depth knowledge of the highly complex IFC object model is required to develop IFC-compliant software. It has proven quite difficult to read the huge amount of building data stored in an IFC file, extract the information needed by a particular application, and correctly update the IFC file with new data. To make this work easier for developers not familiar with the IFC, Olof Granlund Oy has developed a new development tool, BSPro COM-Server for IFC Files. Using this tool, a software developer of new or existing tools can achieve IFC compatibility with a quite reasonable amount of work.

A database perspective on geospatial data modeling

We study the representation and manipulation of geospatial information in a database management system (DBMS). The geospatial data model that we use as a basis hinges on a complex object model, whose set and tuple constructors make it efficient for defining not only collections of geographic objects but also relationships among these objects. In addition, it allows easy manipulation of nonbasic types, such as spatial data types. We investigate the mapping of our reference model onto major commercial DBMS models, namely a relational model extended to abstract data types (ADT) and an object-oriented model. Our analysis shows the strengths and limits of the two model types for handling highly structured data with spatial components.

Fractal antennas: a novel antenna miniaturization technique, and applications

Fractal geometry involves a recursive generating methodology that results in contours with infinitely intricate fine structures. This geometry, which has been used to model complex objects found in nature such as clouds and coastlines, has space-filling properties that can be utilized to miniaturize antennas. These contours are able to add more electrical length in less volume. In this article, we look at miniaturizing wire and patch antennas using fractals. Fractals are profoundly intricate shapes that are easy to define. It is seen that even though the mathematical foundations call for an infinitely complex structure, the complexity that is not discernible for the particular application can be truncated. For antennas, this means that we can reap the rewards of miniaturizing an antenna using fractals without paying the price of having to manufacture an infinitely complex radiator. In fact, it is shown that the required number of generating iterations, each of which adds a layer of intricacy, is only a few. A primer on the mathematical bases of fractal geometry is also given, focusing especially on the mathematical properties that apply to the analysis of antennas. Also presented is an application of these miniaturized antennas to phased arrays. It is shown how these fractal antennas can be used in tightly packed linear arrays, resulting in phased arrays that can scan to wider angles while avoiding grating lobes.

Rapid Prototyping Applications in Medicine. Part 1: NURBS-Based Volume Modelling

Rapid prototyping (RP) technology has extended traditional manufacturing applications in areas other than product engineering. Using RP to fabricate custom implants and prostheses for surgical planning and education is now an important area of research. Although, in theory, RP is capable of producing objects of any complexity, designing freeform shapes is difficult using current CAD systems. These CAD systems are geared toward the design of parts manufactured by traditional methods; they do not help designers exploit the extended opportunities offered by RP technology. Medical data cannot be input into these CAD systems directly for further modification and manipulation. The purpose of this project is to explore a new approach for modelling and prototyping biomedical objects. The work extends from volume modelling to RP and medicine. In this paper, Part 1 of two papers, a new approach to modelling complex objects, NURBS-based volume modelling, is proposed. A NURBS representation of volumes is developed to represent not only the surface boundary but also the interior of a 3D object. NURBS-based volume modelling inherits advantages from both NURBS modelling and voxel-based modelling. The key idea of the NURBS-based volume modelling is to exploit the flexibility of NURBS modelling and use the voxelised NURBS volumes as components for constructing complex objects. Part 2 deals mainly with issues of interfacing volume models to RP systems. A new approach to generate STL files through volume modelling and iso-surface extraction is proposed. This approach guarantees the validity of the final STL file inherently. Software development and case studies are also given.

Adaptive context trees and text clustering

In the finite-alphabet context we propose four alternatives to fixed-order Markov models to estimate a conditional distribution. They consist in working with a large class of variable-length Markov models represented by context trees, and building an estimator of the conditional distribution with a risk of the same order as the risk of the best estimator for every model simultaneously, in a conditional Kullback-Leibler sense. Such estimators can be used to model complex objects like texts written in natural language and define a notion of similarity between them. This idea is illustrated by experimental results of unsupervised text clustering.

A spatial model for complex objects with a broad boundary supporting queries on uncertain data

This paper proposes a new data model for spatial databases that supports spatial entities with a broad boundary. The model is proposed as a solution to the problem of handling uncertainty in spatial data. Broad boundaries absorb all the uncertainty by which spatial data are commonly affected and allow computations in presence of uncertainty without rough simplifications of the reality. A specific model for topological relations between regions with a broad boundary is then developed and hierarchically structured topological operators are proposed. Such operators allow users to progressively refine their queries and constitute the basis for a spatial extension to SQL. The model proposed in the paper can be easily integrated into existing data models for spatial databases.

The Relationlog system prototype

AbstractThe Relationlog system is a novel persistent deductive database system for advanced data and knowledge‐based applications. It directly supports the storage and inference of data with complex structures, especially data supported in nested relational and complex‐object models. The Relationlog system supports the Relationlog query language, which is a typed extension of Datalog with tuples and sets and stands in the same relationship to the nested relational and complex‐object models as Datalog stands to the relational model. It also supports an SQL‐like data definition language and a declarative data manipulation language. This article introduces the Relationlog language, discusses the system architecture, the design decisions incorporated within its implementation, and our experience in developing the system. Copyright © 2001 John Wiley & Sons, Ltd.

V-HairStudio: an interactive tool for hair design

Graphical models of natural objects have become increasingly complex and sophisticated. Although researchers have made significant progress in modeling complex objects in the last decade, representing human hair realistically continues to challenge us. It presents problems in all aspects of computer graphics technologies, such as shape modeling, manipulation, rendering, and dynamic simulation. The article introduces a hair-designing system. Based on the cluster hair model, this designing tool provides a rich set of functionality for interactive hairstyle design in two levels of abstraction. The system is more powerful, and at the same time, more convenient and efficient for hair styling and manipulation than previous modeling systems. We can divide existing hair models into two categories: explicit geometric models and volume-density models.

Programmable matter methods

Fine-grained, indefinitely-extended mesh architectures, which can aptly be termed ‘Programmable Matter’, play a complementary rather than competitive role vis-à-vis traditional architectures. Ideal areas of applicability are physical modeling, materials science, interactive modeling of complex objects, image processing, and pattern recognition. Moreover, these architectures are well suited to furnish a viable blueprint for computers built out of atomic-scale components, towards which technology is inexorably leading. In spite of a potentially huge performance gain over conventional computers, programmable matter is currently hard to exploit. In most cases, its raw computational resources do not directly match the structure of problems one might want to apply it to. Since much ad hoc programming is needed to attain a reasonable fraction of the theoretical performance, so far only niche applications have been explored. We are developing a modeling methodology that will give programmable matter a much broader scope of application. This methodology makes extensive use of synthetic dynamics inspired by physics (kinematic transformations, cellular automata and lattice gases, statistical–mechanical ensembles, simulated annealing, simulated staining, texture-locked loops, etc.), but harnesses these dynamics to data-processing tasks of a more general nature as are encountered in a variety of mundane applications. In particular, by means of suitable feedback, the massive pattern-generation resources of cellular automata machines are used to construct flexible pattern recognizers.

Organization of heterogeneous scientific data using the EAV/CR representation.

Entity-attribute-value (EAV) representation is a means of organizing highly heterogeneous data using a relatively simple physical database schema. EAV representation is widely used in the medical domain, most notably in the storage of data related to clinical patient records. Its potential strengths suggest its use in other biomedical areas, in particular research databases whose schemas are complex as well as constantly changing to reflect evolving knowledge in rapidly advancing scientific domains. When deployed for such purposes, the basic EAV representation needs to be augmented significantly to handle the modeling of complex objects (classes) as well as to manage interobject relationships. The authors refer to their modification of the basic EAV paradigm as EAV/CR (EAV with classes and relationships). They describe EAV/CR representation with examples from two biomedical databases that use it.

The Hipparcos transit data: What, why and how?

The Hipparcos Transit Data are a collection of partially reduced, fully calibrated observations of (mostly) double and multiple stars obtained with the ESA Hipparcos astrometry satellite. The data are publicly available, as part of the CD-ROM set distributed with the Hipparcos and Tycho Catalogues (ESA SP--1200, 1997), for about a third of the Hipparcos Catalogue entries including all confirmed or suspected non-single stars. The Transit Data consist of signal modulation parameters derived from the individual transits of the targets across the Hipparcos focal grid. The Transit Data permit re-reduction of the satellite data for individual objects, using arbitrarily complex object models in which time-variable photometric as well as geometric characteristics may be taken into account. We describe the structure and contents of the Transit Data files and give examples of how the data can be used. Some of the applications use standard astronomical software: Difmap or AIPS for aperture synthesis imaging, and GaussFit for detailed model fitting. Fortran code converting the data into formats suitable for these application programs has been made public in order to encourage and facilitate the use of Hipparcos Transit Data.

Determining interference between pairs of solids defined constructively in computer animation

This paper presents theory and implementation of a method for detecting interference between a pair of solid objects. Often at times, when performing simulations, two solids may unwittingly interpenetrate each other. The two components of the system presented in this paper are: (1) a surface representation method to model solid objects; and (2) a method for detecting interference. Body representation of a solid in this system is based upon enveloping each solid with surfaces (called positive entities). Most computer aided design (CAD) systems use solid modeling techniques to represent solid objects. Since most solid models use Boolean operations to model complex objects, a method is presented to envelop complex objects with parametric surfaces. A method for tracing intersection curves between two surfaces is also presented. Discontinuities on surfaces are defined as negative entitics in order to extend the method to complex solids. Determining interference is based upon a numerical algorithm for computing points of intersection between boundary curves and parametrized entities. The existence of segments of these curves inside the boundary of positive and negative entities is established by computing the circulation of a function around the boundary curve. Interference between two solids is then detected. No limitations are imposed on the convexity or simplicity of the boundary curves treated.

Extending SGML to accommodate database functions: A methodological overview

A method for augmenting an SGML document repository with database functionality is presented. SGML (ISO 8879, 1986) has been widely accepted as a standard language for writing text with added structural information that gives the text greater applicability. Recently there has been a trend to use this structural information as meta-data in databases. The complex structure of documents, however, makes it difficult to directly map the structural information in documents to database structures. In particular, the flat nature of relational databases makes it extremely difficult to model documents that are inherently hierarchical in nature. Consequently, documents are modeled in object-oriented databases (Abite-boul, Cluet, & Milo, 1993), and object-relational databases (Holst, 1995), in which SGML documents are mapped into the corresponding database models and are later reconstructed as necessary. However, this mapping strategy is not natural and can potentially cause loss of information in the original SGML documents. Moreover, interfaces for building queries for current document databases are mostly built on form-based query techniques and do not use the “look and feel” of the documents. This article introduces an implementation method for a complex-object modeling technique specifically for SGML documents and describes interface techniques tailored for text databases. Some of the concepts for a Structured Document Database Management System (SDDBMS) specifically designed for SGML documents are described. A small survey of some current products is also presented to demonstrate the need for such a system. © 1997 John Wiley & Sons, Inc.

Adaptive surface data compression

Three-dimensional (3D) visualization techniques are becoming an important tool for medical applications. Computer-generated 3D reconstructions of the human skull are used to build stereolithographic models, which can be used to simulate surgery or to create individual implants. Anatomy-based 3D models are used to simulate the physical behaviour of human organs. These 3D models are usually displayed by a polygonal description of their surface, which requires hundreds of thousands of polygons. For interactive applications this large number of polygons is a major obstacle. We have improved an adaptive compression algorithm that significantly reduces the number of triangles required to model complex objects without losing visible detail and have implemented it in our surgery simulation system. We present this algorithm using human skull and skin data and describe the efficiency of this new approach.

Generic object recognition using multiple representations

Real-world image understanding tasks often involve complex object models which are not adequately represented by a single representational scheme for the various recognition scenarios encountered in practice. Multiple representations, on the other hand, allow different matching strategies to be applied for the same object, or even for different parts of the same object. This paper is concerned with the derivation of hierarchical CAD models having multiple representations — concave/convex edges and straight homogeneous generalized cylinder — and their use for generic object recognition in outdoor visible imagery. It also presents a refocused matching algorithm that uses a hierarchically structured model database to facilitate generic object recognition. Experimental results demonstrating generic recognition of objects in perspective, aerial images are presented.

Generic object recognition using multiple representations

Real-world image understanding tasks often involve complex object models which are not adequately represented by a single representational scheme for the various recognition scenarios encountered in practice. Multiple representations, on the other hand, allow different matching strategies to be applied for the same object, or even for different parts of the same object. This paper is concerned with the derivation of hierarchical CAD models having multiple representations — concave/convex edges and straight homogeneous generalized cylinder — and their use for generic object recognition in outdoor visible imagery. It also presents a refocused matching algorithm that uses a hierarchically structured model database to facilitate generic object recognition. Experimental results demonstrating generic recognition of objects in perspective, aerial images are presented.

Advanced modeling techniques for computer graphics

In the past thirty years, modeling techniques in computer graphics have evolved significantly as the field has matured and attempted to portray the complexities of nature. Polygonal models, patches, points, and lines are insufficient to represent the complexities of natural objects and intricate man-made objects in a manageable and controllable fashion. Higher-level modeling techniques have been developed to provide an abstraction of the model, encode classes of objects, and allow high-level control and specification of the model. The goal of these advanced modeling techniques is to provide a concise, efficient, flexible, and controllable mechanism for specifying and animating models of complex objects and natural phenomena. Most of these advanced modeling techniques can be considered procedural modeling techniques: code segments or algorithms are used to abstract and encode the details of the model instead of explicitly storing vast numbers of low-level primitives. The use of algorithms unburdens the modeler/animator of low-level control, provides great flexibility, and allows amplification of his efforts through parametric control: a few parameters to the model yield large amounts of geometric details (Smith [1984] called this “database amplification”). This survey examines several types of procedural techniques, including fractals, grammar-based models, volumetric procedural models, implicit surfaces, and particle systems.

Unified 3D Models for Multisensor Image Synthesis

A method for modeling three-dimensional objects for multi-sensory images and feature prediction is presented. The object representation is a modified volume-surface octree created using volume intersection based on the object's silhouettes. This representation is easy to construct and is shown to be well adapted for the simulations of the physical processes that affect the generation of the different imagery. A novel technique is developed that eliminates false volumes in the model created during the process of backprojecting the silhouettes in the volume intersection algorithm. This technique is shown to be valid for the important class of objects defined by simple engineering drawings. The elimination of false volumes increases the accuracy of the volumetric fit of the simulated object to the modeled object. The improved model supports the generation of realistic imagery in three imaging modes: video, thermal, and laser radar. Thermal image simulation based on the modeling of complex objects with nonhomogeneities and time-varying heat generation is described. A computationally efficient, implicit finite difference method is described for the simulation of energy flow within objects and between the object surface and the environment, The prediction of laser radar (ladar) images uses a statistical model to predict speckle noise, which allows the synthesis of realistic imagery. Examples of the multisensory imagery produced by this scheme are presented. The imagery and features values predicted by this unified modeling scheme may be used to train multisensorbased object recognition systems.

Unified modeling of non-homogeneous 3D objects for thermal and visual image synthesis

This paper presents a new approach to integrated modeling of 3D objects for generating multi-sensory images. Specifically, the model supports the generation of visual and thermal images under different viewing, ambient and internal conditions. The model also predicts the values of features that are used by multisensory image interpretation systems. A representation known as the volume surface octree is used for object modeling. It is shown that the above representation is well suited for thermal modeling of complex objects with non-homogeneities and heat generation. An improved volume surface octree construction technique is presented. This technique increases storage efficiency without degrading the quality of image synthesis. A technique to incorporate non-homogeneities and heat generation using octree intersection is described. A computationally efficient, implicit finite difference method is described for heat flow simulation of objects with large number of octree nodes and with non-homogeneities. Several examples of the generated thermal and visual images are presented in this paper, which illustrate the usefulness of the approach. The model is designed to be used in a multi-sensor vision system that would use the images and features predicted by this model in a hypothesize-and-verify scheme.