三维图像中边界曲面的抽取与半透明可视化

已有算法在重构及可视化梯度值从高到低变化且包含弱边界的边界曲面时无法分辨弱边界与噪声碎片。针对上述问题,提出边界曲面半透明显示方法。采用半透明显示技术显示边界曲面及附着在其上的小碎片,利用人的智能及知识在观察可视化结果时对小碎片及弱边界进行有效的区分。结果证明,该方法有助于正确理解及完整显示三维图像中梯度值从高到低变化的边界曲面,为进一步的交互式操作去除小碎片提供依据。     

Visualizing Waypoints‐Constrained Origin‐Destination Patterns for Massive Transportation Data

Origin‐destination (OD) pattern is a highly useful means for transportation research since it summarizes urban dynamics and human mobility. However, existing visual analytics are insufficient for certain OD analytical tasks needed in transport research. For example, transport researchers are interested in path‐related movements across congested roads, besides global patterns over the entire domain. Driven by this need, we propose waypoints‐constrained OD visual analytics, a new approach for exploring path‐related OD patterns in an urban transportation network. First, we use hashing‐based query to support interactive filtering of trajectories through user‐specified waypoints. Second, we elaborate a set of design principles and rules, and derive a novel unified visual representation called the waypoints‐constrained OD view by carefully considering the OD flow presentation, the temporal variation, spatial layout and user interaction. Finally, we demonstrate the effectiveness of our interface with two case studies and expert interviews with five transportation experts.     

Robust Cardiac Function Assessment in 4D PC‐MRI Data of the Aorta and Pulmonary Artery

Four‐dimensional phase‐contrast magnetic resonance imaging (4D PC‐MRI) allows the non‐invasive acquisition of time‐resolved, 3D blood flow information. Stroke volumes (SVs) and regurgitation fractions (RFs) are two of the main measures to assess the cardiac function and severity of valvular pathologies. The flow rates in forward and backward direction through a plane above the aortic or pulmonary valve are required for their quantification. Unfortunately, the calculations are highly sensitive towards the plane's angulation since orthogonally passing flow is considered. This often leads to physiologically implausible results. In this work, a robust quantification method is introduced to overcome this problem. Collaborating radiologists and cardiologists were carefully observed while estimating SVs and RFs in various healthy volunteer and patient 4D PC‐MRI data sets with conventional quantification methods, that is, using a single plane above the valve that is freely movable along the centerline. By default it is aligned perpendicular to the vessel's centerline, but free angulation (rotation) is possible. This facilitated the automation of their approach which, in turn, allows to derive statistical information about the plane angulation sensitivity. Moreover, the experts expect a continuous decrease of the blood flow volume along the vessel course. Conventional methods are often unable to produce this behaviour. Thus, we present a procedure to fit a monotonous function that ensures such physiologically plausible results. In addition, this technique was adapted for the usage in branching vessels such as the pulmonary artery. The performed informal evaluation shows the capability of our method to support diagnosis; a parameter evaluation confirms the robustness. Vortex flow was identified as one of the main causes for quantification uncertainties.     

牙颌点云数据的显著性特征提取

随着激光扫描测量技术的发展,其数据测量精度的逐渐增高使得获取的几何模型表面点云数据的细节信息越丰富,能更准确的反应物体几何表面特征,但如此海量的点云数据同时也带来对应的技术挑战,海量的点云数据在计算机文件存储、数据后期进一步处理以及软件可视化方面都不方便且效率低下.本文中的算法首先采用栅格法对点云进行空间划分及领域关系的建立,其次利用局部表面拟合的方法估算点云法向量,然后利用点云K领域法的向量求解坐标点的显著性值,最后根据显著性的值构建点云八叉树.该算法实现了对点云显著性特征的提取和对点云数据量的进一步简化,它不仅保留了对点云细节特征保持方面的优势,而且在时间效率上得到了提高.     

基于GM(1,1)预测算法的民航飞机实时轨迹可视算法

针对民航飞机动态飞行可视化中滞后和跳跃问题,研究并提出了一种基于预测的民航飞机实时轨迹可视化算法.算法包括轨迹点预测,目标点行进和误差修正三部分.轨迹点预测基于GM （1,1）算法进行改进,在每次迭代时依据所有先验点和搜索方向动态调整发展系数.目标点行进基于预测坐标点提出TSUS （Time Slice Uniform Speed）算法,TSUS算法保证了在既定时间内目标确实移动到目的地,且能够根据初始速度方向调整轨迹弧度.误差修正采用分段式误差修正策略,以平衡不同情况下精确性和实用性.实验表明,提出的算法模型可用于民航飞机可视轨迹渲染中,且能获得良好的效果,提高系统的可用性和用户体验.     

基于Mashup的用户自定义空间态势可视化表达

当前空间态势可视化方案不能根据快速变化的数据和任务要求实现用户自定义表达。在Web应用领域,Mashup能够将多个不同来源的支持Web API的应用按照一定的模式进行糅合,产生新的Web应用,并利用从外部数据源检索到的内容来创建全新的服务。基于Mashup技术,设计用户自定义的空间态势可视化表达,实现内部Widget之间的数据交互;实现三维和二维态势信息可视化Widget,并能够同步显示空间态势信息;通过网络图层管理进行态势信息的显示管理,实现事件的订阅与发布。实验结果表明,基于Mashup技术的用户自定义空间态势可视化表达能够适应快速变化的任务和数据需求。     

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。     

基于拟插值理论的三维体数据场高精度重建算法

三维体数据场重建是体数据建模与分析的一个非常基础和重要的步骤,重建算法的精度直接决定了数据重采样和后续分析的准确性.文中发展了基于拟插值方法的三维体数据场重建理论,首次提出一种充分利用体数据自身信息与核函数优化相结合的预处理算法.在合理假设的前提下得到重建误差的表述式;然后充分利用三维体数据自身的信息全局优化该误差,使得重建误差在L2意义下达到最小.最后通过丰富的重建实例,显示了文中算法能有效地提高重建精度,并能够更好地保持三维体数据的高频信息.     

基于WebGL的医学图像三维可视化研究

现今医学图像往往与大型的硬件设备和复杂的软件联系在一起, 然而随着互联网技术的发展, 越来越多互联网应用的出现改变了人们对传统本地软件的依赖, 现今医学图像在互联网领域才刚刚起步, 提出了一种在浏览器中实现医学图像的三维可视化的方法, 能够通过成熟的本地医学图像平台(比如3DSlicer)获取医学图像数据, 结合HTML5以及WebGL(Web Graphics Library)来实现医学图像的三维可视化.     

Interactive visual analysis of contrast-enhanced ultrasound data based on small neighborhood statistics

Contrast-enhanced ultrasound (CEUS) has recently become an important technology for lesion detection and characterization in cancer diagnosis. CEUS is used to investigate the perfusion kinetics in tissue over time, which relates to tissue vascularization. In this paper we present a pipeline that enables interactive visual exploration and semi-automatic segmentation and classification of CEUS data.For the visual analysis of this challenging data, with characteristic noise patterns and residual movements, we propose a robust method to derive expressive enhancement measures from small spatio-temporal neighborhoods. We use this information in a staged visual analysis pipeline that leads from a more local investigation to global results such as the delineation of anatomic regions according to their perfusion properties. To make the visual exploration interactive, we have developed an accelerated framework based on the OpenCL library, that exploits modern many-cores hardware. Using our application, we were able to analyze datasets from CEUS liver examinations, being able to identify several focal liver lesions, segment and analyze them quickly and precisely, and eventually characterize them.