Reasoning about geological space: Coupling 3D GeoModels and topological queries as an aid to spatial data selection

Topological relationships between geological objects are of great interest for mining and petroleum exploration. Indeed, adjacency, inclusion and intersection are common relationships between geological objects such as faults, geological units, fractures, mineralized zones and reservoirs. However, in the context of 3D modeling, actual geometric data models used to store those objects are not designed to manage explicit topological relationships. For example, with Gocad^© software, topological analyses are possible but they require a series of successive manipulations and are time consuming. This paper presents the development of a 3D topological query prototype, TQuery, compatible with Gocad^© modeling platform. It allows the user to export Gocad^© objects to a data storage model that regularizes the topological relationships between objects. The development of TQuery was oriented towards the use of volumetric objects that are composed of tetrahedrons. Exported data are then retrieved and used for 3D topological and spatial queries. One of the advantages of TQuery is that different types of objects can be queried at the same time without restricting the operations to voxel regions. TQuery allows the user to analyze data more quickly and efficiently and does not require a 3D modeling specialist to use it, which is particularly attractive in the context of a decision-making aid. The prototype was tested on a 3D GeoModel of a continental red-bed copper deposit in the Silurian Robitaille Formation (Transfiguration property, Québec, Canada).     

拓扑关系在图形对象表示与识别中的应用

工程图纸识别中,图形对象的表示方法是研究的重点和难点。在矢量化的基础上提出了一种基于拓扑结构的图形对象表示与识别方法,该方法通过矢量化获得各个图形对象的矢量基元,通过建立矢量基元的影响区域确定各矢量基元的拓扑邻接关系图,进而确定图形对象之间的位置关系,为进一步理解识别工程图纸提供了基本的信息。然后介绍了一个应用实例：圆弧角的识别。在实验中,分别用标准数据和真实图纸进行了测试,实验结果显示该算法具有较高的识别精度和识别效率。     

Non-rigid 3D shape tracking from multiview video

We present a fast and efficient non-rigid shape tracking method for modeling dynamic 3D objects from multiview video. Starting from an initial mesh representation, the shape of a dynamic object is tracked over time, both in geometry and topology, based on multiview silhouette and 3D scene flow information. The mesh representation of each frame is obtained by deforming the mesh representation of the previous frame towards the optimal surface defined by the time-varying multiview silhouette information with the aid of 3D scene flow vectors. The whole time-varying shape is then represented as a mesh sequence which can efficiently be encoded in terms of restructuring and topological operations, and small-scale vertex displacements along with the initial model. The proposed method has the ability to deal with dynamic objects that may undergo non-rigid transformations and topological changes. The time-varying mesh representations of such non-rigid shapes, which are not necessarily of fixed connectivity, can successfully be tracked thanks to restructuring and topological operations employed in our deformation scheme. We demonstrate the performance of the proposed method both on real and synthetic sequences.     

Development of a semantic product modeling system for initial hull structure in shipbuilding

In the initial stage of ship design, designers represent geometry, arrangement, and dimension of hull structures, which correspond to product model information, with 2D geometric primitives such as points, lines, arcs, and drawing symbols on 2D drawings. However, designers must translate the product model information defined on the 2D drawings more intelligently in the following design stages. Thus, design semantics could be lost and design processes that follow could be delayed because of errors by mistranslating the information. Here, design semantics mean design intents of the designer, that is, functions and structures which the product must have.In this study, a semantic product model data structure of an initial ship hull structure was proposed, and a semantic product modeling system was developed based on the proposed data structure. The proposed data structure can store semantic product model information such as product design results with the use of 2D wire frame geometrical data, part attributes, and design knowledge. Hence, this information can be used to generate a 3D solid model and production material information for CAPP as needed.The applicability of the proposed data structure and the developed system was verified by applying them to the deadweight 300,000 ton of Very Large Crude oil Carrier’s product modeling procedure. The application results showed that the proposed data structure and the developed system can be efficiently used for overall initial ship design environment.     

基于四面体的三维地质模型剖切算法研究

为了获取三维地质体任意方向的剖面图,在四面体建模的基础上,利用面与面之间的相切关系以及四面体剖切后拓扑关系的一致性,在三角形自分解基础上完成了三维地质体的任意剖切,并在VC环境下利用OpenGL对该剖切进行了显示。仿真结果表明,该方法实现了三维地质体任意方向的剖切处理,提高了绘制地质剖面图的效率。     

地质断层三维可视化模型的构建方法与实现技术

全面而系统地研究了地质断层三维可视化构模的原理、方法及实施过程.针对地质断层三维构模的特点与要求,设计了一种基于边界表示、面向地质实体并兼顾拓扑关系的三维矢量数据模型,以有效地组织和描述包含断层的复杂地质体几何结构模型.提出了断层与地层的统一构模技术,给出了在其实现过程中所遇到的关键问题(如断层面的推演拟合、地层层面重构、断层与地层的交切处理与局部重构)的解决方案.基于断层的属性、断层数据所反映的断层面的特征和质量,应用3种方法来拟合断层面.在地层层面重构时,考虑到了断层面在地层面网格加密、插值时的约束和屏蔽作用,实现了具有多值面的逆断层网格生成技术.应用三角网切割算法TRICUT来实现断层与地层的交切处理.通过北京奥运公园场区基岩地质模型中的断层构模实例验证了这些技术方法的有效性.     

形状自适应的二维水印方法

通过对空间数据的拓扑一致性问题的分析,给出了一种基于拓扑的空间数据模型,在此基础上提出了一种空间拓扑规则发现机制.利用所得的空间拓扑规则,判断空间数据是否具有拓扑不一致性,进而采取相应的策略进行拓扑一致性维护,以提高空间数据的质量.     

基于钻孔信息的二维剖面图的三维实体重建*

为了有效地表示地质应用领域的三维实体,针对矿山地质三维数据的特征,提出了基于钻孔信息的地质体分层模型重建策略。给定原始地质钻孔数据,利用自适应神经网络预测地质体横剖面内信息未知区域的品位属性,生成分层数据;结合离散网络模型自动创建相邻数据分层内控制点之间的拓扑关系,由此建立三维实体的表面模型;然后利用OpenGL造型系统对上述模型进行可视化渲染。最后为验证建模方法的有效性,开发了一套地质体三维建模实验系统,并结合实证数据进行了仿真分析。     

军事工程实体信息及数据描述方法研究

针对军事工程真三维连续特性及其实体表达的不确定性,给出了军事工程实体信息及数据描述方法,目的是为视景仿真、毁伤建模与仿真等应用领域提供服务。在表达军事工程地理实体认知的基础上,提出了实体信息描述要求;以概念建模为顶层设计,从地学、几何、拓扑、材质等层面进行抽象,给出了军事工程真三维空间集成建模方法;抽象点、线、面、体等实体,给出了军事工程实体模型集成表达方法,并以UML类模型表达了军事工程实体的数据模型。该方法应用于军事工程实体建模,能够较好地表示军事工程三维空间对象,并能有效支持围绕军事工程实体的各种拓扑操作和军事应用。     

20-sim software for hierarchical bond-graph/block-diagram models

We discuss the modeling and simulation package 20-sim, a tool for modeling and simulation of dynamic behavior of engineering systems. Engineering systems as application domain means that we focus on systems that span multiple physical domains and the information domain. The 20-sim software is an interactive tool, where model entry and model processing are fully integrated. This means that already during model entry and editing, models can be checked on their consistency. 20-sim has its own simulator, using sophisticated numerical integration methods, taken from. internationally accepted numerical libraries. The use of 20-sim is demonstrated by an example, in which a 3-dof scara robot with controller is modeled and simulated.     

Toward a Meta-Model for Computational Engineering

Geometric modeling and finite element analysis have matured in recent decades. Both methods are used extensively in engineering design. However, the link between geometric modeling, physical modeling and finite element analysis is currently cumbersome, error-prone, and ad-hoc. Topological domain modeling provides the missing link. In this paper, we propose a combined topological modeling and finite element modeling method that allows not only topological modeling, but also promotes geometric and physical modeling, by providing a topological base space for the definition of finite element meshes, fields, and the definition and solution of boundary value problems. We call the method the Constructive Topological Domain Method (CTDM). In this method, Primitive Topological Domains (PTDs), each possessing a natural coordinate space, are combined in multiple n-dimensional Cartesian coordinate spaces, called charts, using generalizations of Boolean set operations, to create Constructed Topological Domains (CTDs) capable of acting as the base spaces of fiber bundles. The charts are glued together to create an atlas, within which the CTD is defined. The fiber of the bundle may describe, in addition to geometry, physical fields like density, stress, and temperature. Finite element meshes may be defined upon each of the PTDs from which the CTD is constructed, enabling the definition and solution of boundary value problems, thus avoiding the difficult and messy problem of creating a single finite element mesh to represent the entire CTD. A modified finite element method, to handle the individually meshed PTDs, is described. The boundary conditions may be specified as analytical or as finite element-based fields upon each of the PTDs. The CTDM appears to be a promising approach to robust mathematical and computational modeling of physical objects. Simple examples are presented. ID="A1"Correspondance and offprint requests to: W. Gerstle, Department of Civil Engineering, University of New Mexico, Albuquerque, NM 87131, USA. E-mail: gerstle@unm.edu     

Boolean operations on multi-region solids for mesh generation

An algorithm for Boolean operations on non-manifold models is proposed to allow the treatment of solids with multiple regions (internal interfaces) and degenerate portions (shells and wires), in the context of mesh generation. In a solid modeler, one of the most powerful tools to create three-dimensional objects with any level of geometric complexity is the Boolean set operators. They are intuitive and popular ways to combine solids, based on the operations applied to point sets. To assure that the resulting objects have the same dimension as the original objects, without loose or dangling parts, a regularization process is usually applied after a Boolean operation. In practice, the regularization is performed classifying the topological elements and removing internal or lower-dimensional structures. However, in many engineering applications, the adopted geometric model may contain idealized internal parts, as in the case of multi-region models, or lower-dimensional parts, as in the case of solids that contain dangling slabs that are represented as zero-thickness surfaces or wireframes in the model. Therefore, the aim of this work is the development of a generic algorithm that allows the application of the Boolean set operations in a geometric modeling environment applied to finite and boundary element mesh generation. This environment adopts a non-manifold boundary representation that considers an undefined number of topological entities (group concept), and works with objects of different dimensions and with objects not necessarily plane or polyhedral (parametric curved surfaces). Numerical examples are presented to illustrate the proposed methodology.     

三维渗流有限元软件GWSS开发与应用

针对复杂地质条件的三维地质建模、复杂建筑物的几何建模和复杂防渗排水系统作用下渗流场精细模拟等三维渗流场有限元分析的难点问题,采用IDL开发面向水工结构和岩土工程的渗流有限元分析软件GWSS（Ground Water Simulation System）.该软件包括系统控制模块、数据管理模块、前处理模块、计算模块、后处理模块和制图输出模块等六大模块.前处理模块具有基于钻孔和钻孔剖面的三维地质建模、几何建模与有限元网格生成等功能;计算模块主要用于各种闸坝、堤防、隧道和地下洞室等渗流问题的计算分析等;后处理模块可显示各渗流要素的三维云图和任意截面的二维云图等.GWSS已经在国内四十多个工程的渗流计算中得到应用和检验.     

Feature-based 3D non-manifold freeform object construction

This paper presents a novel technique for modeling a 3D non-manifold freeform model around a 3D reference model. To represent both the design abstractions and the incomplete topological information, a new non-manifold data structure is first defined. Our data structure embodies the functional vitalities of both the boundary representation data structure and the complex-based data structure. Along with our data structure, a set of topological operators is defined to manipulate the entities in the data structure. Based on the non-manifold data structure and the topological operators, we develop a technique to construct 3D freeform objects around a reference model. Intuitive 2D sketches are adopted to specify the detailed profile of the object constructed. The construction method is feature-based – every reference model has pre-defined features, and the feature template of the constructed object is related to the features of the reference model by feature node encoding. Therefore, the surfaces derived from one reference model can be regenerated automatically on another reference model with the same features. The geometry coverage of our geometric modeling approach includes both manifold and non-manifold 3D freeform objects.     

Knowledge modeling for design decisions

In this paper, we share our experience in modeling and representing design knowledge relevant for engineering design decisions. We define an object model where classes are used to capture design standards and requirements relevant to designed objects. The traditional object model is customized to the representation of design knowledge in two major ways: (1) Classes representing design objects are augmented with design validation information. (2) Associations between classes are made explicit and used to reduce the redundancy and maintain the consistency of the knowledge. We define the semantics of the resulting object model and formulate the axioms that define its consistency. The object model is defined in the context of stamping design knowledge.     

Algebraic Specification of a 3D-Modeler Based on Hypermaps

We present the algebraic specification of a prototype interactive geometric modeler for 3D objects, whose topologies are represented by 3-dimensional generalized maps. After a reminder of some topological models, particularly maps and extensions, we begin with the more general frame of n-dimensional hypermaps. We specify algebraically a hierarchy of operations on hypermaps and generalized maps, which are embedded in a 3-dimensional Euclidean space. We make precise the modeling area and give the main functionalities of the modeler. We detail high-level operations on 3D objects, and some technical features of this software. Some constructions are explained using pictures. We show that hypermaps and algebraic specification constitute an efficient formal frame for developing large pieces of software in the area of boundary representation.     

Enhanced NURBS modeling and visualization for large 3D geoengineering applications: An example from the Jinping first-level hydropower engineering project,China

Large engineering projects with complex underlying geologic structures require 3D geological integration and analysis. Presented is an example of a large hydroelectric dam, highlighting the need for 3D visualization and modeling as a requirement for the engineering design and construction process. Due to the complex nature of these projects, geological analysis using 3D modeling is commonly necessary. In this paper we present an integrated 3D geological modeling methodology for the analysis of large amounts of exploration data, and subsequent geological interpretation based on the non-uniform rational B-spline (NURBS) technique, the triangulated irregular network (TIN) algorithm and boundary representation. The procedural details and application of the proposed approach are demonstrated with reference to an actual hydropower engineering project. The new approach offered a good scheme to solve the inconsistencies among storage, accuracy and operational speed of the model. A 3D model was developed and validated using testing data from the engineering project. Visual analysis of the 3D model helps engineers to comprehend the complexity of geological structures, and enables arbitrary cutting, rock-mass quality classification, and digital drilling.     

层状地质体建模与可视化

针对已有的层状地质体模型不便进行分析的弱点，提出一个改进模型．该模型不仅可以显式地表示层状地质体的结构元素，而且可以显式地表示它们的空间关系．利用此模型开发的相应软件分别应用于霍林河煤矿床、天津热储层和苍山星球撞击构造的建模和可视化中，均取得良好效果。