Hardware-assisted visibility sorting for unstructured volume rendering

Harvesting the power of modern graphics hardware to solve the complex problem of real-time rendering of large unstructured meshes is a major research goal in the volume visualization community. While, for regular grids, texture-based techniques are well-suited for current GPUs, the steps necessary for rendering unstructured meshes are not so easily mapped to current hardware. We propose a novel volume rendering technique that simplifies the CPU-based processing and shifts much of the sorting burden to the GPU, where it can be performed more efficiently. Our hardware-assisted visibility sorting algorithm is a hybrid technique that operates in both object-space and image-space. In object-space, the algorithm performs a partial sort of the 3D primitives in preparation for rasterization. The goal of the partial sort is to create a list of primitives that generate fragments in nearly sorted order. In image-space, the fragment stream is incrementally sorted using a fixed-depth sorting network. In our algorithm, the object-space work is performed by the CPU and the fragment-level sorting is done completely on the GPU. A prototype implementation of the algorithm demonstrates that the fragment-level sorting achieves rendering rates of between one and six million tetrahedral cells per second on an ATI Radeon 9800.     

体绘制技术在医学可视化中的新发展

科学计算可视化体绘制算法能反映出体数据的内部信息，在医学，它已经从辅诊断发展成为辅助治疗的重要手段，体可视化技术是医学可视化的重要研究内容，其处理过程包括体数据的获取，模型的建立，数据的映射，绘制等操作，该文介绍了医学可视化中常使用的几种光照模型，针对基于图象空间和对象空间两种体绘制算法，介绍了它们的基本思想方法，并详细阐述了在近期的主要加速技术和提高图象质量方法的新进展，最后给出了实验数据和结论。     

GPU加速的台风可视化方法

自然现象的可视化是计算机图形学和虚拟现实领域的重要研究内容。对传统光线投射算法分析的基础上进行改进,提出基于球壳体的光线投射算法。将GPU运用于球壳体数据场的体绘制,设计了基于球壳体数据场的顶点着色程序和像素着色程序。同时,对台风源数据格式进行解析,生成了用于台风可视化的体数据,采用提出的算法实现了台风云层和因子的可视化。实验结果表明,本文基于GPU的球壳体光线投射算法在球体表面较好地实现了实时台风可视化效果。     

Dynamic load balancing for parallel polygon rendering

Using parallel processing for visualization speeds up computer graphics rendering of complex data sets. A parallel algorithm designed for polygon scan conversion and rendering is presented which supports fast rendering of highly complex data sets using advanced lighting models. Dedicated graphics rendering engines do not necessarily suit such data sets, although they can support real-time update of moderately complex scenes using simple lighting. Advantages to using a software-based approach include the feasibility of adding special rendering features to the program and the capability of integrating a parallel scientific application with a parallel graphics renderer. A new work decomposition strategy presented, called task adaptive, is based on dynamically partitioning the amount of computational work left at a given time. The algorithm uses a heuristic for dynamic task decomposition in which image space tasks are partitioned without requiring interruption of the partitioned processor. A sophisticated memory referencing strategy lets local memory access graphics data during rendering. This permits implementation of the algorithm on a distributed memory multiprocessor. An in-depth analysis of the overhead costs accompanying parallel processing shows where performance is adequate or could be improved     

利用峰值线交替扫描法实现曲面消隐

科学可视化将数据和图形图像有机地结合起来，用图形图像直观地展示数据。要生成直观的三维图形，必须进行消隐。对形如z=f(x，y)函数关系的图形，由于网格结点高度z(i，j)的任意性以及规则网格纵横截面的交错性，消隐有时比较困难，需要研究曲面消隐，找出一套有效的消隐算法。在峰值线法(浮动水平线算法)消隐的基础上，提出了一种用于实现形如z=f(x，y)函数关系的图形消隐的峰值线交替扫描法，给出了实施步骤和实例。用该集成消隐方法可方便地实现矩形域上函数z=f(x，y)的数据显示。     

Visualizing and animating the winged-edge data structure

The winged- and half-edge data structures are commonly used representations for polyhedron models. Due to the complexity, students in an introductory course to computer graphics usually have difficulty in handling these data structures and developing applications. This paper describes the authors’ effort in the development of a visualization and animation tool for teaching and learning these data structures. This tool also includes a simple pseudo-code-like language for algorithm design. Instructors may employ this tool for presentation and demonstration purposes. Students may use the simple language to develop and experiment with new algorithms before their actual implementation. The visualization and animation system may be used to explore and understand the relationship among mesh elements and algorithm execution.     

一种新的基于顶点聚类的网格简化算法

在计算机图形学中,经常采用多边形网格来描述物体模型.由于绘制时间和存储量 与多边形的数量成正比,过于庞大的物体网格模型通常是不实用的.模型简化在计算机动画、 虚拟现实和交互式可视化等计算机图形应用领域有着广阔的应用前景.为此提出一种新的基 于顶点聚类的网格简化算法.该算法利用八叉树对网格进行自适应划分,给出了一种基于点 到平面距离的有效的误差控制方法,并能在用户指定的误差范围内通过使原始网格中的顶点 聚类达到大量简化的目的.该算法实现简单,速度快且能很好地保持边界特征.给出的一组图 例说明了该算法的有效性.     

一种新的基于顶点聚类的网格简化算法1)

In computer graphics,models are often discribed by polygonal meshes.Because the rendering and storage cost is proportional to the number of polygons,too large models are not practical.Model simplification techniques are widely used in computer graphics fields such as computer animation,virtual reality and interactive scientific visualization.In this paper a new algorithm of mesh simplification based on vertex clustering is presented.The algorithm adopts octree structure to subdivide the mesh model adaptively.A new error control method is also presented.The implementation of the algorithm is simple and it runs very fast.Examples illustrate the efficiency of the algorithm.     

超级计算机图形学和可视化

近两年,超级计算机、计算机图形学和科学可视化是三个引人注目的论题。今天,大量的计算机应用问题是运用超级计算机以及图形系统和科学可视化来解决的。本文介绍了超级计算机图形学产生和发展的背景,着重阐述了更高级的图形学及其应用的研究与发展,总结了超级计算机可视化的研究现状和发展趋势。最后,本文指出,基于超级计算机图形学的可视化时代已经到来。     

基于动态纹理载入的大规模数据场体绘制

为克服图形硬件对传统纹理映射体绘制的限制,提出了一种在普通PC上进行大规模数据场体绘制的有效方法。该方法中,体数据被划分为合适大小的数据块,这些数据块被动态的载入图形硬件,并利用3维纹理映射进行绘制。在整个绘制过程中,仅有一个数据块存储在图形硬件上,有效地提高了对大规模体数据的绘制能力。同时,充分利用目前PC图形硬件成熟的可编程特性,通过对梯度的实时计算来减少在传统纹理映射体绘制中巨大的内存消耗。实验结果表明,该方法在普通PC上可以对超过纹理内存容量的大规模体数据进行交互式体绘制。     

Interactive examination of surface quality on car bodies

The use of reflection lines and specular high lights for the quality control of car body surfaces is an important issue in the development process of a car. The interactive examination is based on standard graphics tools such as the SceneViewer of OpenInventor which simulates reflection lines by using striped environment maps. The interpolation of texturing and shading values is critical and requires high quality meshes. Thus, element shape and size are essential. In this paper we present a new technique for the tessellation of trimmed surfaces. The result of the algorithm is a 2-manifold mesh with a low triangle count and a triangulation pattern which is best suited for the visualization.     

“内部排序算法”可视化教学软件的设计与实现

介绍了利用C#开发"内部排序算法"可视化教学软件的方法,实现了快速排序、冒泡排序、堆排序、直接插入排序、折半插入排序等基本算法的动态演示。软件动态演示排序算法的抽象性、动态性,使学生直观、清晰地掌握学习排序算法,从而达到辅助教学,提高教学效果的目的。     

基于Shear-Warp算法的三维地震数据场体绘制

利用三维可视化软件包,采用Shear—Warp算法实现地震数据的模型可视化,并给出了具体算法流程。实验结果表明此算法可提高地震数据的体绘制速度,实现地震数据解释的实时交互式绘制,为地质勘探提供可视化依据。     

数据可视化在物流系统中的应用研究

数据可视化技术是通过计算机图形和图像处理技术,把数据转换成图形或者图像,在屏幕上显示出来。以达到清晰有效地传达与沟通信息的作用。简述了数据可视化的概念,阐述了数据可视化在物流系统中可行的技术架构,分析了数据可视化技术在物流系统中的应用现状和前景。     

Design and implementation of an efficient integer count sort in CUDA GPUs

We describe experience on design and implementation of an efficient count sort algorithm on Compute Unified Device Architecture graphics processing units. The novelty of this work is twofold. At first, we propose a count sort algorithm for integers that needs no synchronization at its last step and thus, offers superior performance. At second, this work contributes ad hoc techniques for optimizing the performance of the algorithm on Compute Unified Device Architecture‐enabled graphics processing units. Copyright © 2011 John Wiley & Sons, Ltd.     

直接选择排序可视化设计与实现

针对学生在学习数据结构抽象的排序算法时难以理解的问题,采用目前应用最多的java面向对象开发语言,并使用MYECLIPS集成开发环境进行开发,实现了直接选择排序的可视化。形象、清晰、直观地展现了排序的动态过程,可以很好地激发学生的学习兴趣,提高教学成果。     

Fermi架构下超声成像组织运动可视化并行算法

在临床超声实时成像系统中组织运动情况是医生想要获取的重要诊断信息, 例如心脏运动. 基于线积分卷积的二维矢量场可视化技术可以同时展现运动矢量场的强度和方向. 但这一算法在处理时涉及大量的复杂计算, 尤其是流线追踪处理部分, 使其成为临床实时成像系统中的一大性能提升瓶颈. 为此研究并提出了一种基于新兴的高性能并行计算平台Fermi架构GPU(graphics processing unit图形处理单元)的并行运动可视化算法. 数据测试结果显示, 与基于CPU的实现相比, 采用Fermi架构的GPU处理不仅可     

A particle system for interactive visualization of 3D flows

We present a particle system for interactive visualization of steady 3D flow fields on uniform grids. For the amount of particles we target, particle integration needs to be accelerated and the transfer of these sets for rendering must be avoided. To fulfill these requirements, we exploit features of recent graphics accelerators to advect particles in the graphics processing unit (GPU), saving particle positions in graphics memory, and then sending these positions through the GPU again to obtain images in the frame buffer. This approach allows for interactive streaming and rendering of millions of particles and it enables virtual exploration of high resolution fields in a way similar to real-world experiments. The ability to display the dynamics of large particle sets using visualization options like shaded points or oriented texture splats provides an effective means for visual flow analysis that is far beyond existing solutions. For each particle, flow quantities like vorticity magnitude and A2 are computed and displayed. Built upon a previously published GPU implementation of a sorting network, visibility sorting of transparent particles is implemented. To provide additional visual cues, the GPU constructs and displays visualization geometry like particle lines and stream ribbons.     

High-quality extraction of isosurfaces from regular and irregular grids

Isosurfaces are ubiquitous in many fields, including visualization, graphics, and vision. They are often the main computational component of important processing pipelines (e.g. , surface reconstruction), and are heavily used in practice. The classical approach to compute isosurfaces is to apply the Marching Cubes algorithm, which although robust and simple to implement, generates surfaces that require additional processing steps to improve triangle quality and mesh size. An important issue is that in some cases, the surfaces generated by Marching Cubes are irreparably damaged, and important details are lost which can not be recovered by subsequent processing. The main motivation of this work is to develop a technique capable of constructing high-quality and high-fidelity isosurfaces. We propose a new advancing front technique that is capable of creating high-quality isosurfaces from regular and irregular volumetric datasets. Our work extends the guidance field framework of Schreiner et al. to implicit surfaces, and improves it in significant ways. In particular, we describe a set of sampling conditions that guarantee that surface features will be captured by the algorithm. We also describe an efficient technique to compute a minimal guidance field, which greatly improves performance. Our experimental results show that our technique can generate high-quality meshes from complex datasets.