Using Wavefront Tracing for the Visualization and Optimization of Progressive Lenses

Progressive addition lenses are a relatively new approach to compensate for defects of the human visual system. While traditional spectacles use rotationally symmetric lenses, progressive lenses require the specification of free-form surfaces. This poses difficult problems for the optimal design and its visual evaluation.
This paper presents two new techniques for the visualization of optical systems and the optimization of progressive lenses. Both are based on the same wavefront tracing approach to accurately evaluate the refraction properties of complex optical systems.
We use the results of wavefront tracing for continuously re-focusing the eye during rendering. Together with distribution ray tracing, this yields high-quality images that accurately simulate the visual quality of an optical system. The design of progressive lenses is difficult due to the trade-off between the desired properties of the lens and unavoidable optical errors, such as astigmatism and distortions. We use wavefront tracing to derive an accurate error functional describing the desired properties and the optical error across a lens. Minimizing this error yields optimal free-form lens surfaces.
While the basic approach is much more general, in this paper, we describe its application to the particular problem of designing and evaluating progressive lenses and demonstrate the benefits of the new approach with several example images.     

Overview + Detail Visualization for Ensembles of Diffusion Tensors

A Diffusion Tensor Imaging (DTI) group study consists of a collection of volumetric diffusion tensor datasets (i.e., an ensemble) acquired from a group of subjects. The multivariate nature of the diffusion tensor imposes challenges on the analysis and the visualization. These challenges are commonly tackled by reducing the diffusion tensors to scalar‐valued quantities that can be analyzed with common statistical tools. However, reducing tensors to scalars poses the risk of losing intrinsic information about the tensor. Visualization of tensor ensemble data without loss of information is still a largely unsolved problem. In this work, we propose an overview + detail visualization to facilitate the tensor ensemble exploration. We define an ensemble representative tensor and variations in terms of the three intrinsic tensor properties (i.e., scale, shape, and orientation) separately. The ensemble summary information is visually encoded into the newly designed aggregate tensor glyph which, in a spatial layout, functions as the overview. The aggregate tensor glyph guides the analyst to interesting areas that would need further detailed inspection. The detail views reveal the original information that is lost during aggregation. It helps the analyst to further understand the sources of variation and formulate hypotheses. To illustrate the applicability of our prototype, we compare with most relevant previous work through a user study and we present a case study on the analysis of a brain diffusion tensor dataset ensemble from healthy volunteers.     

Information Visualization Evaluation Using Crowdsourcing

Visualization researchers have been increasingly leveraging crowdsourcing approaches to overcome a number of limitations of controlled laboratory experiments, including small participant sample sizes and narrow demographic backgrounds of study participants. However, as a community, we have little understanding on when, where, and how researchers use crowdsourcing approaches for visualization research. In this paper, we review the use of crowdsourcing for evaluation in visualization research. We analyzed 190 crowdsourcing experiments, reported in 82 papers that were published in major visualization conferences and journals between 2006 and 2017. We tagged each experiment along 36 dimensions that we identified for crowdsourcing experiments. We grouped our dimensions into six important aspects: study design & procedure, task type, participants, measures & metrics, quality assurance, and reproducibility. We report on the main findings of our review and discuss challenges and opportunities for improvements in conducting crowdsourcing studies for visualization research.     

Using GPU Shaders for Visualization

GPU shaders seem used mostly for gaming and other forms of entertainment and simulation. But they have less-obvious visualization uses, for the same reasons that interest the gaming community: improved appearance and performance. This column looks at the use of shaders and the OpenGL shading language (GLSL) in two common visualization applications: point clouds and contour cutting planes.     

Visualization of Anomalies Using Mixture Models

Anomaly detection is important to learn from major past events and to prepare for future crises. We propose a new anomaly detection method that visualizes multivariate data in a 2- or 3-dimensional space based on the probability of belonging to a mixture component and the probability of not belonging to any components. It helps to visually understand not only the magnitude of anomalies but also the relationships among anomalous and normal samples. This may provide new knowledge in the data, since we can see it from a different viewpoint. We show the validity of the proposed method by using both an artificial and an economic time series.     

基于Matlab的地表温度反演可视化系统

陆地表面温度(LST)是区域和全球尺度上陆地表面物理过程的一个关键参数,它综合了地表和大气相互作用以及能量交换的结果,研究地表温度对全球能量平衡的研究有着重要的意义.在项目已采用的昼/夜法和遗传算法基础上,利用Matlab强大的科学运算能力和高质量的图形用户界面设计能力,设计开发了地表温度反演可视化系统.系统主要由文件、反演地表温度、反演地表组分温度和帮助四大功能模块组成,实现了大气校正、温度反演和图像显示的一体化,提高了单纯利用文件读取进行温度反演的效率和可视化程度.最后选取温带半干旱地区的河北省怀来县Terra、Aqua卫星上的MODIS数据为例,通过系统完成了温度反演的全过程,验证了反演系统的可行性.     

Constrained Visualization Using the Shepard Interpolation Family

This paper discusses the problem of visualizing data where there are underlying constraints that must be preserved. For example, we may know that the data are inherently positive. We show how the Modified Quadratic Shepard method, which interpolates scattered data of any dimensionality, can be constrained to preserve positivity. We do this by forcing the quadratic basis functions to be positive. The method can be extended to handle other types of constraints, including lower bound of 0 and upper bound of 1—as occurs with fractional data. A further extension allows general range restrictions, creating an interpolant that lies between any two specified functions as the lower and upper bounds.     

Using Social Visualization to Motivate Social Production

In this paper we argue that social visualization can motivate contributors to social production projects, such as Wikipedia and open source development. As evidence, we present CodeSaw, a social visualization of open source software development that we studied with real open source communities. CodeSaw mines open source archives to visualize group dynamics that currently lie buried in textual databases. Furthermore, CodeSaw becomes an active social space itself by supporting comments directly inside the visualization. To demonstrate CodeSaw, we apply it to a popular open source project, showing how the visualization reveals group dynamics and individual roles. The paper concludes by presenting evidence that CodeSaw, and social visualization more generally, can motivate contributors to social production projects if the visualization leaves the laboratory and makes it to the community visualized.      

一种超图的区域型可视化方法

针对超图绘制中超边表达困难、绘制算法复杂的问题,提出一种超图的快速可视化方法.该方法将超边节点沿其走势线垂线方向向两侧扩展,获得超边中各节点的扩展点;对扩展点根据位置关系重新组合,使用Catmull-Rom算法连接各扩展点,获得超边表示区域的平滑边界曲线;将超边表示区域划分为对偶子段和独立子段,并分别使用三角带和三角扇模式填充;最后根据色相环理论对超边表示区域进行着色,以增强各条超边的区分度.实验结果表明,文中方法能够对超图数据结构进行快速可视化,使用闭合区域包围所有超边节点,从而实现直观、有效的超边表示;对于100个节点/30条超边以内的超图,该方法的绘制效率能够满足实时交互的要求.     

用Java构建的基于Web的气象可视化系统

随着Internet的飞速发展，在网上发布气象信息，应用网络进行交互式合作，成为气象可视化应用的一个重要发展方向，Java远程方法调用（RMI）通过Web链接使得对远程对象调用如同对本地对象调用一样简捷。     

图像边缘细节增强方法及VC++实现

介绍了图像边缘细节增强技术,详细说明了边缘细节增强方法中的梯度算子、拉普拉斯算子和反锐化掩模的原理算法,并给出了Windows平台下以VisualC++6.0为开发工具实现及各种算法的处理结果。     

旅行的笔触

朱炜是一名艺术家,这也决定了他的旅行和常人不一样。每到一个地方,他最关注的是那的博物馆有什么,最在乎的是站在艺术大家作品前和他们进行的时空交流。     

Evaluating 2D Flow Visualization Using Eye Tracking

Flow visualization is recognized as an essential tool for many scientific research fields and different visualization approaches are proposed. Several studies are also conducted to evaluate their effectiveness but these studies rarely examine the performance from the perspective of visual perception. In this paper, we aim at exploring how users’ visual perception is influenced by different 2D flow visualization methods. An eye tracker is used to analyze users’ visual behaviors when they perform the free viewing, advection prediction, flow feature detection, and flow feature identification tasks on the flow field images generated by different visualizations methods. We evaluate the illustration capability of five representative visualization algorithms. Our results show that the eye‐tracking‐based evaluation provides more insights to quantitatively analyze the effectiveness of these visualization methods.     

基于栅格空间V图的无人机路径规划

在进行无人机低空飞行的路径规划时,障碍物已不能简单的简化为点状;针对该问题,首先将带有面状障碍物的图片格式地图以像素为单位进行栅格划分,在定义了栅格距离后,进行距离变换,并运用边界跟踪方法生成栅格空间V图;其次,将A-Star算法的启发思想引入到蚁群算法中,并修改了启发信息计算公式以使蚁群算法更适合于栅格空间优化;最后,以栅格空间V图为初始路径,运用改进的蚁群算法进行优化选择,得到了满意的路径规划结果。     

一种利用XSLT实现GML文档可视化的技术

介绍了GML和SVG规范，分析了XSLT的结构和工作原理，最后举例说明了应用XSLT技术实现GML文档的可视化。     

Comparative Visualization of Molecular Surfaces Using Deformable Models

The comparison of molecular surface attributes is of interest for computer aided drug design and the analysis of biochemical simulations. Due to the non‐rigid nature of molecular surfaces, partial shape matching is feasible for mapping two surfaces onto each other. We present a novel technique to obtain a mapping relation between two surfaces using a deformable model approach. This relation is used for pair‐wise comparison of local surface attributes (e.g. electrostatic potential). We combine the difference value as well as the comparability as derived from the local matching quality in a 3D molecular visualization by mapping them to color. A 2D matrix shows the global dissimilarity in an overview of different data sets in an ensemble. We apply our visualizations to simulation results provided by collaborators from the field of biochemistry to evaluate the effectiveness of our results.     

Processing Optimal Sequenced Route Queries Using Voronoi Diagrams

The Optimal Sequenced Route (OSR) query strives to find a route of minimum length starting from a given source location and passing through a number of typed locations in a specific sequence imposed on the types of the locations. In this paper, we propose a pre-computation approach to OSR query in both vector and metric spaces. We exploit the geometric properties of the solution space and theoretically prove its relation to additively weighted Voronoi diagrams. Our approach recursively accesses these diagrams to incrementally build the OSR. Introducing the analogous diagrams for the space of road networks, we show that our approach is also efficiently applicable to this metric space. Our experimental results verify that our pre-computation approach outperforms the previous index-based approaches in terms of query response time. This research has been funded in part by NSF grants EEC-9529152 (IMSC ERC), IIS-0238560 (PECASE), IIS-0324955 (ITR), IIS-0534761, and unrestricted cash gifts from Google and Microsoft. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF.

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改进的图标法进行平面向量场可视化

图标法是常见的平面矢量场可视化方法。但是当传统的图标法用在大数据集且变化不是很明显的矢量场中时,图像可能会显得比较混乱。本文基于矢量场中局部矢量近似平行的原理,将传统的图标法做一改进。将局部范围内变化不明显的矢量,用该范围内的某一矢量来代替,这样所得的图像不再是规整的图标图像,图像上图标的多少是由矢量变化的明显程度来决定的。矢量变化不大的地方,矢量图标少,反之,矢量变化较大的地方,矢量图标多。这种方法使得所显示的矢量场不显得混乱,又能表达出矢量场的方向和大小。     

SVG和XML-RPC实现的Web方式网络拓扑显示

提出了用SVG结合XML-RPC的方法来实现Web方式的网络拓扑显示：用SVG描述网络拓扑,提供无失真缩放、动画等表现形式;用XML-RPC实现客户端网络拓扑图与服务端的通信,完成用户对网络拓扑图的编辑、保存等交互动作。给出了采用这一方案的网络拓扑显示模块的设计与实现,以及实际应用的效果。     

基于A*算法的高超声速飞行器航迹规划方法

为了提高A*算法应用于高超声速飞行器航迹规划时的效率和稳定性,并保证航迹可飞性,提出基于改进型变步长稀疏A*算法的航迹规划方法。首先根据飞行器飞行区域不存在地形限制的特点,在规划过程中采取变步长策略,有效地提高了远程规划时的稳定性和效率;然后依赖飞行器的过载计算最大转弯角和爬升/俯冲角,根据计算角度构建规划空间,同时将飞行器飞行过程燃料/时间、航向、飞行高度、航迹末端、禁飞区域等约束用于规划空间优化,减少扩展节点的数量,进一步提高了规划效率并保证航迹的可飞性;最后基于威胁约束设计特殊的代价函数,保障了飞行安全和航迹规划的稳定性。仿真结果表明:规划出的航迹满足高超声速飞行器各种飞行要求,能避开各种威胁,规划时间短,稳定性好。得到的航迹能够作为航迹跟踪控制系统设计时的参考输入。