大型隧道工程三维数值分析的并行计算方法

建立了黄浦江某大型越江隧道的三维精细非线性有限元模型,采用接触均衡的并行计算技术,解决了大型隧道工程数值模拟时规模庞大的问题。数值模拟了越江隧道的静应力场,比较了两种不同分区方案对并行加速比的影响。数值模拟结果能够为大型隧道工程设计提供参考依据。     

A survey of content based 3D shape retrieval methods

Recent developments in techniques for modeling, digitizing and visualizing 3D shapes has led to an explosion in the number of available 3D models on the Internet and in domain-specific databases. This has led to the development of 3D shape retrieval systems that, given a query object, retrieve similar 3D objects. For visualization, 3D shapes are often represented as a surface, in particular polygonal meshes, for example in VRML format. Often these models contain holes, intersecting polygons, are not manifold, and do not enclose a volume unambiguously. On the contrary, 3D volume models, such as solid models produced by CAD systems, or voxels models, enclose a volume properly. This paper surveys the literature on methods for content based 3D retrieval, taking into account the applicability to surface models as well as to volume models. The methods are evaluated with respect to several requirements of content based 3D shape retrieval, such as: (1) shape representation requirements, (2) properties of dissimilarity measures, (3) efficiency, (4) discrimination abilities, (5) ability to perform partial matching, (6) robustness, and (7) necessity of pose normalization. Finally, the advantages and limitations of the several approaches in content based 3D shape retrieval are discussed.

Parallel computing of 3D smoking simulation based on OpenCL heterogeneous platform

Open Computing Language (OpenCL) is an open royalty-free standard for general purpose parallel programming across Central Processing Units (CPUs), Graphic Processing Units (GPUs) and other processors. This paper introduces OpenCL to implement real-time smoking simulation in a virtual surgery training simulation system. Firstly, the Computational Fluid Dynamics (CFD) is adopted to construct the real-time smoking simulation model based on the Navier?CStokes (N-S) equations of an incompressible fluid under the condition of normal temperature and pressure. Then we propose a parallel computing technique based on OpenCL to accomplish the parallel computing of smoking simulation model on CPU and GPU, respectively. Finally, we render the smoke in real time by using a three-dimensional (3D) texture volume rendering method. Experimental results show that the parallel computing technique we have proposed achieve a satisfactory effect on image quality and rendering rate both on CPU and GPU.     

多模式3维视频形状编码

目的 具有立体感和高端真实感的3D视频正越来越受到学术界和产业界的关注和重视,未来在3D影视、机器视觉、远程医疗、军事航天等领域将有着广泛的应用前景。对象基3D视频是未来3D视频技术的重要发展趋势,其中高效形状编码是对象基3D视频应用中的关键问题。但现有形状编码方法主要针对图像和视频对象,面向3D视频的形状编码算法还很少。为此,基于对象基3D视频的应用需求,提出一种基于轮廓和链码表示的高效多模式3D视频形状编码方法。方法 对于给定的3D视频形状序列逐帧进行对象轮廓提取并预处理后,进行对象轮廓活动性分析,将形状图像分成帧内模式编码图像和帧间预测模式编码图像。对于帧内编码图像,基于轮廓内链码方向约束和线性特征进行高效编码。对于帧间编码图像,采用基于链码表示的轮廓基运动补偿预测、视差补偿预测、联合运动与视差补偿预测等多种模式进行编码,以充分利用视点内对象轮廓的帧间时域相关性和视点间对象轮廓的空域相关性,从而达到高效编码的目的。结果 实验仿真结果显示所提算法性能优于经典和现有的最新同类方法,压缩效率平均能提高9.3%到64.8%不等。结论 提出的多模式3D视频形状编码方法可以有效去除对象轮廓的帧间和视点间冗余,能够进行高效编码压缩,性能优于现有同类方法,可广泛应用于对象基编码、对象基检索、对象基内容分析与理解等。     

模型显著域上的形状调控和处理

基于3维数字模型的显著性度量和显著域处理技术,提出一种模型显著域上的形状调控和处理方法。该方法首先基于曲面上采样顶点处局部投影高度的Gaussian加权平均双边滤波定义数字模型的表面显著性;然后利用定义在模型显著域上的形状调控函数——显著域低通形状调控函数、显著域高通形状调控函数和显著域增强形状调控函数,使模型的显著特征得到有效抑制、提升和增强,实现了针对模型表面显著特征的形状调控和处理。实验结果表明,该方法能够方便快速地实现3维数字模型的不同形状造型效果。     

D3DPR:基于Direct3D9的并行图形绘制系统

根据Direct3D9图形库的特征,提出了支持Direct3D9应用程序级透明并行图形绘制系统D3DPR的系统结构及其实现原理.D3DPR分为资源分配和资源绘制2类逻辑节点.通过资源分配节点并行图形库DPGL的截取技术和资源绘制节点的重构技术,任何单机的Direct3D9应用程序都不需要经过修改即可实时转变为由PC集群并行绘制,从而得到更高的绘制性能和高分辨率的多屏拼接显示效果,为用户提供具有更强真实感和沉浸感的虚拟环境.     

基于分层策略的三维非刚性模型配准算法

在三维非刚性模型分析中,通常需要对不同姿态下的模型进行配准。针对传统配准算法存在复杂度高、计算量大、精确度低等问题,提出一种新的基于分层策略的三维非刚性模型配准算法。首先,定义热核签名函数为模型的标量域,使用同源聚类算法提取模型的特征点和特征区域,进而提出三维几何模型的树形表示方法:它的根节点为三维几何模型,内部节点为模型的特征区域,叶节点为包含在相应区域的特征点。然后,根据三维几何模型的树形表示提出模型的分层配准算法。在SHREC 2010模型配准数据集上对比分析了分层配准算法、推广的多维尺度变换算法（GMDS）和博弈论方法在等距变换、孔洞、小孔洞、尺度变换、局部尺度变换、重采样、噪声、散粒噪声以及拓扑变换等情况下的性能。实验结果表明,在以上三维几何模型数据受干扰的情况下,分层配准算法的准确性明显优于GMDS方法和博弈论方法,同时具有较低的计算复杂度。     

一个并行三维图形处理系统的设计

本文介绍了一三维图形并行处理系统的设计，着重研究了三维图形处理系统体系结构问题，具体设计了一种并行处理结构，讨论了系统硬件和软件的设计，描述了系统的工作过程，分析了系统的特点     

Justification of a certain algorithm for shape optimization in 3D elasticity

The trabecular bone adapts its form to mechanical loads and is able to form structures that are both lightweight but very stiff. In this sense, it is a problem (for the Nature or living entities) similar to the structural optimization, especially the topology optimization. The structural optimization system developed by the authors previously was based directly on the bio-mechanical models. The paper aims to clarify the approach of using the bio-mechanical models of the trabecular bone remodelling phenomenon as a base for the structural optimization. The justified algorithm for shape optimization mimics the natural phenomenon to satisfy the condition of constant value of the strain energy density on the structural surface, issuing from the considerations in the area of mechanics. The main body of the paper contains the analysis of the stiffness optimization problem in the framework of speed method approach to shape optimization. The given numerical example (cantilever beam in bending) includes the influence of the structural surface curvature on the optimization procedure. The presented in the paper approach can be used as a method of structural optimization unrelated already to trabecular bone remodelling phenomenon.     

Perceptual-saliency extremum lines for 3D shape illustration

Owing to their efficiency for conveying perceptual information of the underlying shape and their pleasing perceiving in visual aesthetics experience, line drawings are now becoming a widely used technique for illustrating 3D shapes. Using a center-surrounding bilateral filter operator on Gaussian-weighted average of local projection height between mesh vertices and their neighbors, a new perceptual-saliency measure which can depict surface salient features, is proposed in this paper. Due to the definition of perceptual-saliency measure, our perceptual-saliency extremum lines can be considered as the ridge-valley lines of perceptual-saliency measure along the principal curvature directions on triangular meshes. The experimental results demonstrate that these extremum lines effectively capture and depict 3D shape information visually, especially for archaeological artifacts.     

Characterization of 3D shape parts for semantic annotation

3D content stored in big databases or shared on the Internet is a precious resource for several applications, but unfortunately it risks being underexploited due to the difficulty of retrieving it efficiently. In this paper we describe a system called the “ShapeAnnotator” through which it is possible to perform non-trivial segmentations of 3D surface meshes and annotate the detected parts through concepts expressed by an ontology. Each part is connected to an instance that can be stored in a knowledge base to ease the retrieval process based on semantics. Through an intuitive interface, users create such instances by simply selecting proper classes in the ontology; attributes and relations with other instances can be computed automatically based on a customizable analysis of the underlying topology and geometry of the parts. We show how our part-based annotation framework can be used in two scenarios, namely for the creation of avatars in emerging Internet-based virtual worlds, and for product design in e-manufacturing.     

Comparative analysis of shape descriptors for 3D objects

Multimedia Tools and Applications - One of the basic characteristics of an object is its shape. Several research areas in mathematics and computer science have taken an interest in object...     

Hybrid Parallel Bundle Adjustment for 3D Scene Reconstruction with Massive Points

Bundle adjustment(BA) is a crucial but time consuming step in 3D reconstruction.In this paper,we intend to tackle a special class of BA problems where the reconstructed 3D points are much more numerous than the camera parameters,called Massive-Points BA(MPBA) problems.This is often the case when high-resolution images are used.We present a design and implementation of a new bundle adjustment algorithm for efficiently solving the MPBA problems.The use of hardware parallelism,the multi-core CPUs as well as GPUs,is explored.By careful memory-usage design,the graphic-memory limitation is effectively alleviated.Several modern acceleration strategies for bundle adjustment,such as the mixed-precision arithmetics,the embedded point iteration,and the preconditioned conjugate gradients,are explored and compared.By using several high-resolution image datasets,we generate a variety of MPBA problems,with which the performance of five bundle adjustment algorithms are evaluated.The experimental results show that our algorithm is up to 40 times faster than classical Sparse Bundle Adjustment,while maintaining comparable precision.     

A computational framework for the 3D structure determination of viruses with unknown symmetry

The protein shell of all virus structures resolved to this date exhibit some form of symmetry, most of them are spherical viruses with icosahedral symmetry; the study of viruses whose symmetry is not known, of structures which do not exhibit any symmetry, as well as the study of the genetic material of a virus are considerably more challenging. Increasing the resolution of the structure determination and solving structures with no symmetry represents a quantum leap in virus structure determination based upon electron microscopy. Computing is a major component of the structure determination process. Nowadays it is not feasible to increase the resolution of the structure determination of large macromolecules like viruses or to solve structures with no symmetry without novel parallel algorithms and environments enabling structural biologists to use parallel systems, clusters of workstations, or providing access to grid computing.