大坝地震反应数据场快速体绘制算法

为了弥补传统体绘制静止画面时，不能明确判断场值集中部位的不足，提出了一种快速体绘制算法，针对大坝地震反应有限元计算数据场，根据每个单元法线与视线夹角最小的表面来选择剖切方向，将单元剖切成多个四边形面后进行颜色融合和叠加，大大提高了体绘制速度，实现了动态观察体绘制图，从而清楚地分析场值集中部位。     

并行分布式体绘制算法的设计

体绘制是一种需要大量计算资源和内存资源的可视化任务，本文提出一种并行分布式体绘制算法，对绘制任务进行适当剖分，使用连网的工作站进行计算，有效地加快了图形绘制速度。     

直接体绘制技术在地质体三维可视化中的应用研究*

将直接体绘制技术应用于地质体三维可视化,首先对原始钻孔数据进行插值、网格化等预处理得到满足直接体绘制需要的规则体数据,从而建立反映地层分布的地质体三维标量数据场;然后用直接体绘制技术绘制三维地质体,避免了体元建模方法中在对地质体进行剖切等操作时必须要解决的剖面与体元之间复杂的判断求交等过程。采用该方法实现了对某地区地质体的三维可视化。     

医学体数据三维可视化改进算法综述

医学体数据三维可视化技术有着广泛的应用前景。近年来为加快绘制速度，提高成像质量和节省存储空间提出了许多改进算法，本文总结了这些算法，为进一步研究奠定了基础。     

基于物质分类的频域体绘制算法

本文提出了一种新的频域体绘制算法，与以前的频域体绘制（ＦＶＲ－Ｆｒｅｑｕｅｎｃｙ ｄｏｍａｉｎ Ｖｏｌｕｍｅ Ｒｅｎｄｅｒｉｎｇ）算法不同的是，该算法借鉴并引入了传统空域绘制算法中普遍采用分类过程，从而使得生成的图象更加接近于空域方法的结果，在些算法的基础上，文中又提出了一种在图象效果上类似于传统空域面绘制算法的方法。该方法通过频域重采样过程中运用Ｌａｐｌａｃｅ算子，使得数据场的三维物质边界面得到     

基于曲面建模的三维地质体体绘制研究

体绘制技术因为其相对于面绘制技术能够更好地反映三维体的真实结构,因而越来越受到人们的重视.提出了一种基于曲面建模的地质体体绘制方法,并在此基础上引入原始钻孔点的穷举搜索来获得散乱点以生成曲面.并根据现场数据的特征采用了适合中小型数据量插值拟合计算的改进谢别德插值来实现曲面的生成.产生曲面之后,使用了现在被普遍采用的基于图像空间序的光线投射算法完成地质体的体绘制,并在此基础上实现了剖切,缩放等三维体的交互操作.     

直接体绘制加速算法综述

针对当前体绘制存在的软件加速算法,将其分为空间剖分技术、光线相关、物空间相关和基于图像绘制技术等四类,分别介绍其算法基本内容.最后利用MIN-MAX八叉树加速算法设计一个直接体绘制系统.     

加速透视投影体绘制技术研究

针对可视化中透视体绘制计算量大、耗时较长的不利因素,算法将三维体数据集按照三种主要的观察方向(X,Y,Z)抽取出切片数据,对切片数据进行错切操作,设立一个与切片平行的中间图像平面;在绘制中间图像时使用图形硬件所提供的纹理混和功能;最终图像经过中间图像的变形而得到,从而使绘制速度得到了较大提高。     

基于GPU的工业CT体数据剖切显示

为了优化工业CT体数据的3维显示性能,必须提高剖切显示的速度,为此可将基于图形处理器（GPU）的编程方法应用到体数据显示算法中来,由于GPU可利用可编程流水线来加速渲染复杂场景,而且图形应用程序可调用片段着色程序来实现剖切显示算法,这样几十个可编程片段处理器可同时对多个像素点进行采样。为了提高剖切显示速度,提出了一种基于GPU的CT体数据剖切显示算法,并首先阐述了如何加载和预处理工业CT体数据,然后给出了Cg应用程序和片段着色程序的设计步骤;最后对工业CT扫描体数据进行了剖切实验。实验结果表明,基于GPU的剖切显示算法不仅生成的图像清晰,具有稳定和较高的帧率,而且计算速度是CPU算法的2～9倍,可满足了工业CT图像系统快速3维显示的要求。     

一种基于图像序列轮廓三维重建表面的任意切面图像提取及纹理映射有效方法

针对三维重建后的表面模型的任意剖切,首先通过对象的序列轮廓去掉图像背景,然后计算其模型及图像空间中包围盒和剖切平面的交面,利用向量叠加原理及立方体线性插值方法快速提取交面图像,经Alpha测试后映射到模型空间中相应切面上.实验表明,该方法在克服面绘制技术不能体现内部数据缺点的同时,有效地提高了模型任意剖切时剖面纹理绘制速度.     

基于GPU加速的轮廓毛发绘制技术

在采用层状纹理切片来表达真实感毛发的方法中,模型轮廓处毛发切片的计算与生成需要耗费很多时间,影响绘制效率。针对此问题,提出一种利用图形处理器（GPU）可编程能力的轮廓毛发快速生成技术。该技术通过为顶点设计一种“边信息”的数据结构,将轮廓边的检测及轮廓毛发切片的生成完全转移到了GPU中进行,从而大大加速了轮廓毛发的处理,提高了真实感毛发的绘制效率。     

OpenGL图形消隐质量的改善

分析了用一般方法在OpenGL中进行图形消隐时存在消隐质量问题的产生原因,提出了两种具体的改善消隐质量方法,即模块缓冲区校验法和多边形偏移量修正法,在方法说明之后,给出了具体开发过程实例,并对它们进行了比较,指出其分适用的条件。     

对3D Warping分解的高质量虚拟视点绘制方法

基于深度图像的虚拟视点绘制（DIBR）作为自由视点视频应用中的核心问题,由其获得的任意视频的质量和速度对于自由视点视频的发展至关重要。为解决经典DIBR方法存在的重叠、空洞、伪影,以及由于重采样导致的细小裂纹问题以提高虚拟视点图像质量,提出了一种基于改进的3D Warping过程的虚拟视点绘制方法。该方法从整个3D Warping过程出发,将3D Warping过程分解成两步而无需进行三维建模,并分别在两步中提出了改进的方法。在第一步中,通过在变换矩阵中引入可调的系数对三维参数进行修改;在第二步中,主要针对由于重采样导致的细小的裂纹问题,提出了自适应一投多算法,在兼顾时间复杂度的同时改善了裂纹问题。实验结果表明,无论从主观质量还是客观评价标准来看,该方法都能够显著提高虚拟视点绘制的图像质量。     

Modified kinetic flux vector splitting (m-KFVS) method for compressible flows

To resolve many flow features accurately, like accurate capture of suction peak in subsonic flows and crisp shocks in flows with discontinuities, to minimise the loss in stagnation pressure in isentropic flows or even flow separation in viscous flows require an accurate and low dissipative numerical scheme. The first order kinetic flux vector splitting (KFVS) method has been found to be very robust but suffers from the problem of having much more numerical diffusion than required, resulting in inaccurate computation of the above flow features. However, numerical dissipation can be reduced by refining the grid or by using higher order kinetic schemes. In flows with strong shock waves, the higher order schemes require limiters, which reduce the local order of accuracy to first order, resulting in degradation of flow features in many cases. Further, these schemes require more points in the stencil and hence consume more computational time and memory. In this paper, we present a low dissipative modified KFVS (m-KFVS) method which leads to improved splitting of inviscid fluxes. The m-KFVS method captures the above flow features more accurately compared to first order KFVS and the results are comparable to second order accurate KFVS method, by still using the first order stencil.     

道路网络在三维虚拟场景中的应用

计算道路网络在其所覆盖地理范围内带来的区域划分情况,针对道路网络在三维虚拟场景,特别是基于LOD地形模型的虚拟场景中的可视化出现的问题,该文提出一种基于模版阴影锥算法的道路绘制方法。仿真结果表明,该方法可在地形表面上精确绘制出道路 网络。     

Disjoint convex shell and its applications in mesh unfolding

In this work, we study a geometric structure called disjoint convex shell or simply DC-shell. A DC-shell of a polyhedron is a set of pairwise interior disjoint convex objects that collectively approximate the given polyhedron. Preventing convex objects from overlapping enables faster and robust collision response and more realistic fracturing simulation. Without the disjointness constraint, a physical realization of the approximation becomes impossible. This paper investigates multiple approaches that construct DC-shells from shapes that are either composed of overlapping components or segmented into parts. We show theoretically that, even under this rather simplified setting, constructing DC-shell is difficult.To demonstrate the power of DC-shell, we studied how DC-shell can be used in mesh unfolding, an important computational method in manufacturing 3D shape from the 2D material. Approximating a given polyhedron model by DC-shells provides two major benefits. First, they are much easier to unfold using the existing unfolding methods. Second, they can be folded easily by both human folder or self-folding machines. Consequently, DC-shell makes paper craft creation and design more accessible to younger children and provides chances to enrich their education experiences.     

An algebraic approach to shape-from-image problems

This paper presents a new method for recovering three-dimensional shapes of polyhedral objects from their single-view images. The problem of recovery is formulated in a constrained optimization problem, in which the constraints reflect the assumption that the scene is composed of polyhedral objects, and the objective function to be minimized is a weighted sum of quadric errors of surface information such as shading and texture. For practical purpose it is decomposed into the two more tractable problems: a linear programming problem and an unconstrained optimization problem. In the present method the global constraints placed by the polyhedron assumption are represented in terms of linear algebra, whereas similar constraints have usually been represented in terms of a gradient space. Moreover, superstrictness of the constraints can be circumvented by a new concept ‘position-free incidence structure’. For this reason the present method has several advantages: it can recover the polyhedral shape even if image data are incorrect due to vertex-position errors, it can deal with perspective projection as well as orthographic projection, the number of variables in the optimization problem is very small (three or a little greater than three), and any kinds of surface information can be incorporated in a unifying manner.     

An Efficient Method for Rendering Underwater Optical Effects Using Graphics Hardware

The display of realistic natural scenes is one of the most important research areas in computer graphics. Therendering of water is one of the essential components. This paper proposes an efficient method for renderingimages of scenes within water. For underwater scenery, the shafts of light and caustics are attractive and importantelements. However, computing these effects is difficult and time‐consuming since light refracts when passingthrough waves. To address the problem, our method makes use of graphics hardware to accelerate the computation.Our method displays the shafts of light by accumulating the intensities of streaks of light by using hardware colorblending functions. Making use of a Z‐buffer and a stencil buffer accelerates the rendering of caustics. Moreover,by using a shadow mapping technique, our method can display shafts of light and caustics taking account ofshadows due to objects. ACM CSS: I. 3.1 Computer Graphics—Hardware Architecture, I. 3.7 Computer Graphics—Three‐DimensionalGraphics and Realism     

Image-Based Network Rendering of Large Meshes for Cloud Computing

Recent advances in sensing and software technologies enable us to obtain large-scale, yet fine 3D mesh models of cultural assets. However, such large models cannot be displayed interactively on consumer computers because of the performance limitation of the hardware. Cloud computing technology is a solution that can process a very large amount of information without adding to each client user’s processing cost. In this paper, we propose an interactive rendering system for large 3D mesh models, stored on a remote environment through a network of relatively small capacity machines, based on the cloud computing concept. Our system uses both model- and image-based rendering methods for efficient load balance between a server and clients. On the server, the 3D models are rendered by the model-based method using a hierarchical data structure with Level of Detail (LOD). On the client, an arbitrary view is constructed by using a novel image-based method, referred to as the Grid-Lumigraph, which blends colors from sampling images received from the server. The resulting rendering system can efficiently render any image in real time. We implemented the system and evaluated the rendering and data transferring performance.     

用弯曲体纹理构造发型

毛发的造型和绘制技术是当今计算机图形学中的一个突出难题.因为头发形状精细、数量庞大,传统的造型和绘制技术很难达到令人满意的效果.针对人的头发,提出并在数学上表示出了弯曲体纹理.接着参照理发师制作发型的过程,将头皮曲面予以特别处理,并以人头部的形状为依据,给出简单发型的构造方法.然后根据头皮曲面上四边形的结构关系,用插值方法将简单造型予以修正和发展,给出了几个发型构造的实例.最后绘制出具有较为真实效果的发型图.