Data Intermixing and Multi-volume Rendering

The main difference between multi-volume rendering and mono-volume rendering is data intermixing. In this paper, we present three levels of data intermixing and their rendering pipelines in direct multi-volume rendering, which discriminate image level intensity intermixing, accumulation level opacity intermixing, and illumination model level parameter intermixing. In the context of radiotherapy treatment planning, different data intermixing methods are applied to three volumes, including CT volume, Dose volume, and Segmentation volume, to compare the features of different data intermixing methods.     

基于Web的时变体数据的体绘制方法

传统Web体绘制方法主要集中在利用服务器端进行预处理和绘制任务,浏览器端仅用于呈现绘制结果,这样会造成服务器负载过高,同时,当绘制参数发生更改时,必须向服务器请求新的绘制结果,这样也易受网络延迟的影响。为了解决以上问题,实现在浏览器本地进行体绘制和交互,本文提出一种基于WebGL的体绘制方法,以时变体数据为例,在浏览器端实现光线投射体绘制算法。同时,为了提升绘制效率和减少内存占用,本文基于维度压缩方法,优化时变体数据的预处理过程。最后,本文设计了Web体绘制系统,引入暴风时变数据集以验证方法的有效性,结果表明,本文方法能够在浏览器本地对时变体数据进行体绘制,绘制时间在50ms以下,帧速率可达到50 FPS以上,同时支持实时交互,并且当绘制参数发生更改时,系统能够直接在浏览器端进行重新绘制。     

体视化方法综述

综述了体视化研究的历史及近年来体视化技术的研究现状和发展情况,其中包括体数据的预处理、三维物体表面重建、直接体视、体图形学等各方面方法的优缺点,并预测了体视化的未来研究趋势。     

Fast Volume Rendering and Data Classification Using Multiresolution in Min‐Max Octrees

Large‐sized volume datasets have recently become commonplace and users are now demanding that volume‐rendering techniques to visualise such data provide acceptable results on relatively modest computing platforms. The widespread use of the Internet for the transmission and/or rendering of volume data is also exerting increasing demands on software providers. Multiresolution can address these issues in an elegant way. One of the fastest volume‐rendering alrogithms is that proposed by Lacroute & Levoy ¹ , which is based on shear‐warp factorisation and min‐max octrees (MMOs). Unfortunately, since an MMO captures only a single resolution of a volume dataset, this method is unsuitable for rendering datasets in a multiresolution form. This paper adapts the above algorithm to multiresolution volume rendering to enable near‐real‐time interaction to take place on a standard PC. It also permits the user to modify classification functions and/or resolution during rendering with no significant loss of rendering speed. A newly‐developed data structure based on the MMO is employed, the multiresolution min‐max octree, M ³ O, which captures the spatial coherence for datasets at all resolutions. Speed is enhanced by the use of multiresolution opacity transfer functions for rapidly determining and discarding transparent dataset regions. Some experimental results on sample volume datasets are presented.     

State-of-the-art in Large-Scale Volume Visualization Beyond Structured Data

Volume data these days is usually massive in terms of its topology, multiple fields, or temporal component. With the gap between compute and memory performance widening, the memory subsystem becomes the primary bottleneck for scientific volume visualization. Simple, structured, regular representations are often infeasible because the buses and interconnects involved need to accommodate the data required for interactive rendering. In this state-of-the-art report, we review works focusing on large-scale volume rendering beyond those typical structured and regular grid representations. We focus primarily on hierarchical and adaptive mesh refinement representations, unstructured meshes, and compressed representations that gained recent popularity. We review works that approach this kind of data using strategies such as out-of-core rendering, massive parallelism, and other strategies to cope with the sheer size of the ever-increasing volume of data produced by today's supercomputers and acquisition devices. We emphasize the data management side of large-scale volume rendering systems and also include a review of tools that support the various volume data types discussed.     

基于PC系统平台实现快速体绘制技术

体绘制技术可将难于理解的三维数据场转化成直观的图像，作为一种最具前景的科学计算可视化技术在医学影像方面有着极强的实用意义。由于体绘制算法需要强大的计算能力，在通常的PC系统上难以实现满足交互式应用的绘制速度，因此阻碍了其普及。研究PC系统上的快速体绘制技术，无疑具有重要的意义．本文使用Shear-warp的体绘制算法，并利用Intel公司的SSE2扩展指令对整个绘制过程进行加速，实现了基于中高档桌面PC系统平台的快速体绘制应用。     

光线投射算法中重采样的设计和实现

体绘制技术在医学成像和科学可视化领域有着极为广泛的应用，但由于其巨大的计算开销，限制了其实时动态体绘制的应用，因此许多研究人员致力于静态体绘制加速算法的研究，为了提高体绘制速度。分析了三维规则数据场重采样的原理。光线投射算法中对3D数据场重采样的实现方法；根据具体重建对象，提出了在3D数据场重采样中采用球形包围盒的方法，给出了人体头部和眼球的三维可视化结果，实验表明：这种算法能有效地减少重采样的计算量，并使求交计算更加简单。     

A Video-Based 3D-Reconstruction of Soccer Games

In this paper we present SoccerMan, a reconstruction system designed to generate animated, virtual 3D views from two synchronous video sequences of a short part of a given soccer game. After the reconstruction process, which needs also some manual interaction, the virtual 3D scene can be examined and 'replayed' from any viewpoint. Players are modeled as so-called animated texture objects, i.e. 2D player shapes are extracted from video and texture-mapped onto rectangles in 3D space. Animated texture objects have shown very appropriate as a 3D representation of soccer players in motion, as the visual nature of the original human motion is preserved. The trajectories of the players and the ball in 3D space are reconstructed accurately. In order to create a 3D reconstruction of a given soccer scene, the following steps have to be executed: 1) Camera parameters of all frames of both sequences are computed (camera calibration). 2) The playground texture is extracted from the video sequences. 3) Trajectories of the ball and the players' heads are computed after manually specifying their image positions in a few key frames. 4) Player textures are extracted automatically from video. 5) The shapes of colliding or occluding players are separated automatically. 6) For visualization, player shapes are texture-mapped onto appropriately placed rectangles in virtual space. SoccerMan is a novel experimental sports analysis system with fairly ambitious objectives. Its design decisions, in particular to start from two synchronous video sequences and to model players by texture objects, have already proven promising.     

基于2D多纹理映射的三维医学图像体绘制技术的改进

提出了一种基于寄存器合成器和多纹理（Multi—Texture）的体绘制方法，它能够进行三线性插值采样，并且能够使用近似归一化的插值梯度进行明暗处理。     

体绘制技术

可视化技术是继计算、实验两大科学研究方法之后的第三种研究方法,体绘制技术作为可视化技术的一个重要分支,已经取得长足发展。对常用体绘制技术进行了分类,并且指出、分析了各自特点及适用场合,为进一步应用、改进这些技术提供参考。     

Collaborative Virtual Simulation Environment for Radiotherapy Treatment Planning

The simulation of Radiotherapy Treatment Planning (RTP) is a normal procedure in oncology clinics carried out on a Simulator machine. The Virtual Simulation of RTP replaces the real Simulator machine with a virtual one by using the CT data sets of a patient instead of the real patient. In this paper, we present a collaborative virtual simulation environment of RTP, named EU-VIRTUOSO, which is based on volume rendering and telecommunication techniques. The RTP procedure is visualised on a virtual patient, which is created by using the CT data of the patient. Different volume rendering and volume interaction techniques, such as DRR, MIP, gradient surface, and iso-surface, supply physicians with high quality rendering images to simulate the real working environment of the Simulator machine. In the collaborative environment, physicians distributed at different locations can work together via network to plan the treatment or to validate the treatment plan on-line by a collaborative application sharing approach. Both concepts virtualised planning and collaborative planning improve the efficiency and accuracy of a radiotherapy treatment while reducing the effort for an individual patient.     

Video-based Approach to Human Animation

A method based on computer vision technologies is presented to determine the 3-D spatial locations of joints or feature points of a human body from human motion video. The proposed method first applies the geometric projection theory to obtain a set of feasible postures in some key frames according to predefined 2D video features and 3D-model features correspondence. Next it makes use of the available skeleton controlled human model to get a feasible posture for each key frame. The method is applied to a series of video images to animate artificial 3D human models.     

基于八叉树快速分类的Shear-Warp 交互式体绘制算法

基于八叉树的快速分类Shear-Warp算法,是三维规则数据场可视化的一种经典算法。它适用于三维重建过程中用户需要交互式地动态调整透明度变换函数,以观察三维实体的不同细节的应用场合。论文对算法进行了深入的研究和局部的优化。论文首先介绍算法原理,然后给出算法实现模型,最后给出实验结果和进一步的研究前景。     

立体可视化——新兴的灵境技术

立体可视化是９０年出现的可视化及计算机图形学的一个重要领域。立体可视化质变计算机图形学带来了一场革命,并在其众多的应用领域中取得了突破性进展,不仅容易实现图形演示的虚拟真实性（灵境）,而且可以将视野深入至复杂物体的内部世界,文语文介绍立体可视化技术的原理,立体数据的生成,处理及演示。     

An Incremental Alignment Algorithm for Parallel Volume Rendering

This paper introduces a data distribution scheme and an alignment algorithm for parallel volume rendering. The algorithm performs a single wrap-around shear transformation which requires only a regular inter-processor communication pattern. The alignment can be implemented incrementally consisting of short distance shifts, thus significantly reducing the communication overhead. The alignment process is a non-destructive transformation, consisting of a single non-scaling shear operation. This is a unique feature which provides the basis for the incremental algorithm.     

Reshaping the Coliseum in Rome: An Integrated Data Capture and Modeling Method at Heritage Sites

The paper describes the process of building Internet‐transmittable, 3‐D digital virtual models of ancient heritage monuments from on‐site data, focusing especially on 3‐D dimensional data acquisition techniques and color processing methods. Section 1 considers project goals and the attendant problems; Section 2 provides a brief summary of state‐of‐the‐art experience and the technologies adopted by the Authors; Section 3 illustrates the key features of the 3‐D color data acquisition methods used as well as the shape and color processing pipeline; Section 4 describes the specific study conducted on single elements and faades of the Coliseum in Rome, while Section 6 outlines future work.     

基于GPU Raycasting算法的矢量/栅格混合绘制研究*

Raycasting体绘制算法由于成像质量高而被广泛应用于体数据的可视化,但当线、面表达的矢量数据和三维栅格表达的体数据同时绘制到同一场景时,由于绘制方法的差异会造成矢量和栅格数据空间遮挡关系不一致。在GPU实现Raycasting算法的基础上,通过矢量和栅格数据先后绘制,采用FBO离屏绘制等技术将矢量数据绘制到深度缓存纹理并在体绘制采样和融合中统一考虑矢栅颜色融合。实验结果表明,该算法在矢量数据非透明模式下能正确处理矢量栅格数据的混合绘制。     

基于数据场相关性的光线投射算法

光线投射算法是体绘制中的经典方法,这一算污具有结构清晰实现便利的特点。但简单的光线投射算法存在采样效率低和绘制精度低的缺点。本文利用数据场的相关性和不等步长的采样方法来改善泡线投射算法的品质,使它既有快速的优点又具有较高的成象精度     

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。     

Spatio‐Temporal Contours from Deep Volume Raycasting

We visualize contours for spatio‐temporal processes to indicate where and when non‐continuous changes occur or spatial bounds are encountered. All time steps are comprised densely in one visualization, with contours allowing to efficiently analyze processes in the data even in case of spatial or temporal overlap. Contours are determined on the basis of deep raycasting that collects samples across time and depth along each ray. For each sample along a ray, its closest neighbors from adjacent rays are identified, considering time, depth, and value in the process. Large distances are represented as contours in image space, using color to indicate temporal occurrence. This contour representation can easily be combined with volume rendering‐based techniques, providing both full spatial detail for individual time steps and an outline of the whole time series in one view. Our view‐dependent technique supports efficient progressive computation, and requires no prior assumptions regarding the shape or nature of processes in the data. We discuss and demonstrate the performance and utility of our approach via a variety of data sets, comparison and combination with an alternative technique, and feedback by a domain scientist.