三维GIS的基本问题与研究进展

经过多年的研究和探索,三维GIS取得了很大成果,成为GIS领域的重要研究内容之一。该文首先分析了三维GIS应实现的功能,然后从三维数据获取、三维空间数据模型、三维空间关系的描述和表达、三维可视化和三维空间分析等几个方面评述了三维GIS的研究进展。     

Java3D在钢结构建模中的应用

Java3D是基于Java平台的、功能强大的面向对象的三维图形应用程序接口(API)，它的设计是对目前流行的诸如OpenGL和Direct3D的3D图形API的重大革新。利用Java3D能使三维建模变得更加快捷和清晰。该文就如何应用Java3D建立三维钢结构模型进行了初步的探讨。     

计算机三维物体实体组建方法的研究

在计算机绘图和三维图像显示,例如激光扫描共焦显微图像、CT图像、MRI图像等的绘制和显示中,三维物体的组建是必不可少的。目前,三维物体的组建都是基于二维物体组建的基础之上。二维物体组建是基于连通性进行二维连通区域检出的,因而三维物体的组建速度比较慢。为此,文章提出一种新方法:围线积分法区域标号和链接表法三维叠片,用于三维图像中三维物体实体的组建。这种方法的基本原理是在三维二值图像中,先采用围线积分法区域标号,组建二维物体切片,再采用链接表法三维叠片,由二维物体切片组建三维实体。这种方法的优点是组建速度比较快。     

基于弹簧质点模型的二维/三维映射算法*

提出了一种用于服装设计的二维/三维映射算法.该算法基于弹簧质点变形模型,服装裁剪片二维到三维映射及三维到二维映射可以在该模型中得到统一的实现.在服装裁剪片二维到三维的映射过程中,二维裁剪片被放置在人体模型附近的初始位置,在缝合力的作用下,裁剪片自动变形并缝合到人体模型上.在服装裁剪片三维到二维映射的过程中,三维裁剪片被初始映射到指定的平面内,在弹性变形力的作用下,逐步变形并得到最终的二维裁剪片.在进行服装裁剪片二维到三维映射的过程中,考虑了干涉检验的问题.     

2D representation of facial surfaces for multi-pose 3D face recognition

The increasing availability of 3D facial data offers the potential to overcome the intrinsic difficulties faced by conventional face recognition using 2D images. Instead of extending 2D recognition algorithms for 3D purpose, this letter proposes a novel strategy for 3D face recognition from the perspective of representing each 3D facial surface with a 2D attribute image and taking the advantage of the advances in 2D face recognition. In our approach, each 3D facial surface is mapped homeomorphically onto a 2D lattice, where the value at each site is an attribute that represents the local 3D geometrical or textural properties on the surface, therefore invariant to pose changes. This lattice is then interpolated to generate a 2D attribute image. 3D face recognition can be achieved by applying the traditional 2D face recognition techniques to obtained attribute images. In this study, we chose the pose invariant local mean curvature calculated at each vertex on the 3D facial surface to construct the 2D attribute image and adopted the eigenface algorithm for attribute image recognition. We compared our approach to state-of-the-art 3D face recognition algorithms in the FRGC (Version 2.0), GavabDB and NPU3D database. Our results show that the proposed approach has improved the robustness to head pose variation and can produce more accurate 3D multi-pose face recognition.     

数字城市中三维数字社区的解决方案

数字社区是数字城市建设的基本单元。该文着重讨论了数字社区的三维解决方案,包括:社区三维数据的获取、社区物业信息三维化管理、社区三维建筑规划、社区三维道路规划、社区地下三维管线、社区网络服务以及社区招商演示等几方面。详细论述了三维可视地理信息系统在三维数字社区的实现中所起的作用。     

A Prototypical 3D Graphical Visualizer for Object-Oriented Systems

is paper describes a framework for visualizing object-oriented systems within a 3D interactive environment.The 3D visualizer represents the structure of a program as Cylinder Net that simultaneously specifies two relationships between objects within 3D virtual space.Additionally,it represents additional relationships on demand when objects are moved into local focus.The 3D visualizer is implemented using a 3D graphics toolkit,TOAST,that implements 3D Widgets 3D graphics to ease the programming task for 3D visualization.     

3D sparse signal recovery via 3D orthogonal matching pursuit

Though many three-dimensional (3D) compressive sensing schemes have been proposed, recovery algorithms in most of these schemes are designed for 1D or 2D signals, which cause some serious drawbacks, e.g., huge memory usage, and high decoder complexity. This paper proposes a 3D separable operator (3DSO) which is able to completely exploit the spatial and spectral correlation to sparsify and samples the 3D signal in three dimensions. A 3D orthogonal matching pursuit (3D-OMP) algorithm is then employed to recover the 3D sparse signal, which is able to reduce the computational complexity of the decoder significantly with guaranteed accuracy. In the proposed algorithm, we represent each 3D signal as a weighted sum of 3D atoms, which allow us to sample the 3D signal with 3D separable sensing operator. Then the best matched atoms are selected to construct the 3D support set, and the 3D signal is optimally recovered from the 3D support set in the sense of the least squares. Experimental results show that the 3D-OMP approach achieves higher recovery quality but requires less computational time than the Kronecker Compressive Sensing (KCS) scheme.     

3D/4DGIS/TGIS现状研究及其发展动态

3D-GIS是目前GIS界最热门的研究项目之一,论文从三维数据获取方式、三维数据模型和结构、三维可视化和三维空间分析等几个方面的研究现状进行评述;在此基础上描述了4DGIS/TGIS的特征、相关技术和发展前景;最后对3D/4DGIS在未来发展中面临的问题进行了探讨。     

一种支持空间拓扑分析的3维数据模型

3维空间数据模型是构建3维空间数据库和3维GIS的基础，有着极为重要的研究意义。为了能更好地表示空间3维对象，提出了一种基于3D-realms的数据模型，它是对基于2D-realms的空间数据模型的3维扩展，并详细给出了该模型的基本定义、语义描述和基于该模型的3维空间对象操作，运用分层的方法可将该模型分为4层：3维几何原语层、3D-realms层、3维基本空间构建要素层和3维基本空间对象层（包括点、线、面和体）。其中，由于每个较低层都是构建较高层中元素的基础，因此可为上层提供支持。实验表明，基于3D-realms的3维空间数据模型不仅能保证拓扑关系的正确性，而且能较好地表示3维空间对象，并能有效地支持3维空间拓扑分析操作。     

On the learning machine for three dimensional mapping

In this paper, we investigate the neural network with three-dimensional parameters for applications like 3D image processing, interpretation of 3D transformations, and 3D object motion. A 3D vector represents a point in the 3D space, and an object might be represented with a set of these points. Thus, it is desirable to have a 3D vector-valued neural network, which deals with three signals as one cluster. In such a neural network, 3D signals are flowing through a network and are the unit of learning. This article also deals with a related 3D back-propagation (3D-BP) learning algorithm, which is an extension of conventional back-propagation algorithm in the single dimension. 3D-BP has an inherent ability to learn and generalize the 3D motion. The computational experiments presented in this paper evaluate the performance of considered learning machine in generalization of 3D transformations and 3D pattern recognition.     

基于人体行为3D模型的2D行为识别

针对行为识别中行为者朝向变化带来的问题, 提出了一种基于人体行为3D模型的2D行为识别算法. 在学习行为分类器时, 以3D占据网格表示行为样本, 提取人体3D关节点作为描述行为的特征, 为每一类行为训练一个基于范例的隐马尔可夫模型(Exemplar-based hidden Markov model, EHMM), 同时从3D行为样本中选取若干帧作为3D关键姿势集, 这个集合是连接2D观测样本和人体3D关节点特征的桥梁. 在识别2D行为时, 2D观测样本序列可以由一个或多个非标定的摄像机采集. 首先在3D关键姿势集中为每一帧2D观测样本寻找与之最匹配的3D关键姿势帧, 之后由行为分类器对2D观测样本序列对应的3D关键姿势序列进行识别. 该算法在训练行为分类器时要进行行为者的3D重构和人体3D关节点的提取, 而在识别2D行为时不再需要进行3D重构. 通过在3个数据库上的实验, 证明该算法可以有效识别行为者在任意朝向下的行为, 并可以适应不同的行为采集环境.     

基于X3D技术的虚拟现实电子商务网站

本文给出了一种结合虚拟现实技术与三维视频技术的电子商务应用的开发过程,通过应用X3D技术,可以充分结合XML技术与VRML技术的优势,更好地被各种主流开发技术所支持,并且使传统的网站用户界面进入了三维的现实应用效果。由于X3D技术是一种发展中的技术,本文使用了Delone & McLean的IS success模型对该网站系统进行了评估,并且分析了X3D技术在现有条件下的相关不足,为该技术的改进和发展提供了有价值的信息和数据。     

Manifold Constrained Transfer of Facial Geometric Knowledge for 3D Caricature Reconstruction

3D caricatures are important attractive elements of the interface in virtual environment such as online game. However, very limited 3D caricatures exist in the real world. Meanwhile, creating 3D caricatures manually is rather costly, and even professional skills are needed. This paper proposes a novel and effective manifold transfer algorithm to reconstruct 3D caricatures according to their original 2D caricatures. We first manually create a small dataset with only 100 3D caricature models and use them to initialize the whole 3D dataset. After that, manifold transfer algorithm is carried out to refine the dataset. The algorithm comprises of two steps. The first is to perform manifold alignment between 2D and 3D caricatures to get a "standard" manifold map; the second is to reconstruct all the 3D caricatures based on the manifold map. The proposed approach utilizes and transfers knowledge of 2D caricatures to the target 3D caricatures well. Comparative experiments show that the approach reconstructs 3D caricatures more effectively and the results conform more to the styles of the original 2D caricatures than the Principal Components Analysis (PCA) based method.     

考古地层的三维重建方法*

基于现有三维可视化技术,分别介绍了3D图形库接口、3D GIS技术、3D GMS技术、虚拟现实技术等可以实现考古地层三维重建的方法,并从地层三维建模的角度比较了各种方法的特点,探讨了较为实用的考古地层三维重建途径.     

Static and dynamic 3D facial expression recognition: A comprehensive survey

Automatic facial expression recognition constitutes an active research field due to the latest advances in computing technology that make the user's experience a clear priority. The majority of work conducted in this area involves 2D imagery, despite the problems this presents due to inherent pose and illumination variations. In order to deal with these problems, 3D and 4D (dynamic 3D) recordings are increasingly used in expression analysis research. In this paper we survey the recent advances in 3D and 4D facial expression recognition. We discuss developments in 3D facial data acquisition and tracking, and present currently available 3D/4D face databases suitable for 3D/4D facial expressions analysis as well as the existing facial expression recognition systems that exploit either 3D or 4D data in detail. Finally, challenges that have to be addressed if 3D facial expression recognition systems are to become a part of future applications are extensively discussed.     

SVG的3D实现

针对SVG在3D图形的描述与绘制上存在局限性的问题,提出了一种SVG的3D实现方法;详细介绍了SVG的2D坐标系到3D坐标系的转换原理,给出了转换到3D坐标系后的SVG-3D图形的绘制与操控流程,并以在3D场景中绘制一个正立方体和圆球体为例,介绍了在HTML页面中采用JavaScript创建3D场景和绘制与操控这2个图形的实现。     

Integrated approach of streaming 3d multimedia contents in real-time for mobile devices

It is popular to watch a 3D video through a 3D display nowadays. However, it is still difficult to enjoy the 3D multimedia contents with a mobile device even if a mobile device with a 3D display is currently introduced into the market. The main technological challenges for watching 3D contents via the mobile devices can be identified as the following: generating and streaming 3D contents. Generating 3D contents requires extra computational resources. Moreover, streaming 3D contents demands additional network bandwidth for receiving and transmitting the 3D data. To overcome these technological challenges, we propose ReMA, a novel 3D video streaming system in this paper. We devised a novel architecture for transmitter, receiver, and a distribution system to efficiently disseminate and generate 3D videos for the mobile devices. We implemented ReMA in a real test-bed and conducted a thorough empirical evaluation study to see the feasibility of streaming 3D contents for the mobile devices. Based on our empirical study, the resulting system presents a great promise in streaming 3D video in real-time to the mobile devices.     

三维有限差分计算中大规模网格生成及显示技术

针对爆炸与冲击问题并行仿真计算软件PMMIC-3D（Parallel Multi-Material in Cell 3D）的计算网格为正交六面体网格的特点,开发与PMMIC-3D接口统一的可对任意复杂三维实体模型进行大规模有限差分网格生成的三维前处理软件MESH-3D.MESH-3D采用CSG和STL模型两种建模方式进行复杂实体建模,并采用基于边的整体切片算法,借鉴计算机图形学中的扫描线填充算法完成三维有限差分网格划分.在绘制网格时,删除网格单元的公共面,大大缩短计算时间和减少存储空间,实现对网格的快速消隐显示.MESH-3D可实现百亿量级网格单元的生成和显示.三维前处理软件MESH-3D的开发有力地支持爆炸与冲击问题的仿真计算.