Simon J. Walton

Glyph-Based Video Visualization for Semen Analysis

The existing efforts in computer assisted semen analysis have been focused on high speed imaging and automated image analysis of sperm motility. This results in a large amount of data, and it is extremely challenging for both clinical scientists and researchers to interpret, compare and correlate the multidimensional and time-varying measurements captured from video data. In this work, we use glyphs to encode a collection of numerical measurements taken at a regular interval and to summarize spatio-temporal motion characteristics using static visual representations. The design of the glyphs addresses the needs for (a) encoding some 20 variables using separable visual channels, (b) supporting scientific observation of the interrelationships between different measurements and comparison between different sperm cells and their flagella, and (c) facilitating the learning of the encoding scheme by making use of appropriate visual abstractions and metaphors. As a case study, we focus this work on video visualization for computer-aided semen analysis, which has a broad impact on both biological sciences and medical healthcare. We demonstrate that glyph-based visualization can serve as a means of external memorization of video data as well as an overview of a large set of spatiotemporal measurements. It enables domain scientists to make scientific observation in a cost-effective manner by reducing the burden of viewing videos repeatedly, while providing them with a new visual representation for conveying semen statistics.

Manipulating, Deforming and Animating Sampled Object Representations

A sampled object representation (SOR) defines a graphical model using data obtained from a sampling process, which takes a collection of samples at discrete positions in space in order to capture certain geometrical and physical properties of one or more objects of interest. Examples of SORs include images, videos, volume datasets and point datasets. Unlike many commonly used data representations in computer graphics, SORs lack in geometrical, topological and semantic information, which is much needed for controlling deformation and animation. Hence it poses a significant scientific and technical challenge to develop deformation and animation methods that operate upon SORs. Such methods can enable computer graphics and computer animation to benefit enormously from the advances of digital imaging technology.

Walking in the Wild – Using an Always-On Smartphone Application to Increase Physical Activity

This multidisciplinary paper reports on a large-scale field trial, designed and implemented by a group of social scientists, computer scientists and statisticians, of a new smartphone-based app for the promotion of walking in everyday life. The app, bActive, is designed for a more diverse range of users than the typical active-lifestyle app, since it requires neither additional equipment nor a great deal of commitment to exercise. As a result, it can raise awareness of walking and promote walking amongst those with only a casual or hesitant engagement with the topic. The 6-week randomised controlled trial with 22-40 year-old male participants (N=152) indicates that bActive prompted users to increase the amount of walking they did by encouraging them to value and increase walking that is incidental to normal everyday activities. Longitudinal data analysis showed that use of the app increased walking by an average of 64% but did not find any evidence to suggest that the inclusion of comparative social feedback improves the impact of such apps on male participants.

Deforming and Animating Discretely Sampled Object Representations

A discretely sampled object representation (DSOR) denes a graphical model using data obtained by a sampling process, which takes a collection of samples at discrete positions in space in order to capture certain geometrical and physical properties of one or more objects of interest. Examples of DSORs include images, videos, volume datasets and point datasets. Unlike many commonly used data representations in computer graphics, DSORs lack in geometrical, topological and semantic information, which is much needed for controlling deformation and animation. Hence it poses a signicant scientic and technical challenge to develop deformation and animation methods that operate upon DSORs. Such methods can enable computer graphics and computer animation to benet enormously from the advances of digital imaging technology. In this state of the art report, we survey a wide-range of techniques that have been developed for manipulating, deforming and animating DSORs. We consider a collection of elementary operations for manipulating DSORs, which can serve as building blocks of deformation and animation techniques. We examine a collection of techniques that are designed to transform the geometry shape of deformable DSORs and pay particular attention to their deployment in surgical simulation. We review a collection of techniques for animating digital characters in DSORs, focusing on recent developments in volume animation.

Analyzing high-dimensional multivaríate network links with integrated anomaly detection, highlighting and exploration

This paper focuses on the integration of a family of visual analytics techniques for analyzing high-dimensional, multivariate network data that features spatial and temporal information, network connections, and a variety of other categorical and numerical data types. Such data types are commonly encountered in transportation, shipping, and logistics industries. Due to the scale and complexity of the data, it is essential to integrate techniques for data analysis, visualization, and exploration. We present new visual representations, Petal and Thread, to effectively present many-to-many network data including multi-attribute vectors. In addition, we deploy an information-theoretic model for anomaly detection across varying dimensions, displaying highlighted anomalies in a visually consistent manner, as well as supporting a managed process of exploration. Lastly, we evaluate the proposed methodology through data exploration and an empirical study.

Visual Multiplexing

The majority of display devices used in visualization are 2D displays. Inevitably, it is often necessary to overlay one piece of visual information on top of another, especially in applications such as multi‐field visualization and geo‐spatial information visualization. In this paper, we present a conceptual framework for studying the mechanisms for overlaying multiple pieces of visual information while allowing users to recover occluded information. We adopt the term ‘multiplexing’ from tele‐ and data communication to encompass all such overlapping mechanisms. We establish 10 categories of visual multiplexing mechanisms. We draw support evidence from both perception literature and existing works in visualization to support this conceptual framework. We examine the relationships between multiplexing and information theoretic measures. This new conceptual categorization provides the much‐needed theory of visualization with an integral component.

Visualizing Cardiovascular Magnetic Resonance (CMR) imagery: challenges and opportunities.

Cardiovascular Magnetic Resonance (CMR) imaging is an essential technique for measuring regional myocardial function. However, it is a time-consuming and cognitively demanding task to interpret, identify and compare various motion characteristics based on watching CMR imagery. In this work, we focus on the problems of visualising imagery resulting from 2D myocardial tagging in CMR. In particular we provide an overview of the current state of the art of relevant visualization techniques, and a discussion on why the problem is difficult from a perceptual perspective. Finally, we introduce a proof-of-concept multilayered visualization user interface for visualizing CMR data using multiple derived attributes encoded into multivariate glyphs. An initial evaluation of the system by clinicians suggested a great potential for this visualisation technology to become a clinical practice in the future.

Interacting with Volume Data: Deformations using Forward Projection

We present a rendering algorithm for the forward projection of volume deformations. Spatial deformations are modeled by allowing the user to define curve skeletons inside the target object. Our rendering method utilises modern consumer graphics hardware and is integrated into an easy to use interface. In addition, we give an analysis of spatial transfer functions computed on the GPU, and give a solution to the problem of cracks appearing in image space when samples are pulled apart.

Categorical Colormap Optimization with Visualization Case Studies

Mapping a set of categorical values to different colors is an elementary technique in data visualization. Users of visualization software routinely rely on the default colormaps provided by a system, or colormaps suggested by software such as ColorBrewer. In practice, users often have to select a set of colors in a semantically meaningful way (e.g., based on conventions, color metaphors, and logological associations), and consequently would like to ensure their perceptual differentiation is optimized. In this paper, we present an algorithmic approach for maximizing the perceptual distances among a set of given colors. We address two technical problems in optimization, i.e., (i) the phenomena of local maxima that halt the optimization too soon, and (ii) the arbitrary reassignment of colors that leads to the loss of the original semantic association. We paid particular attention to different types of constraints that users may wish to impose during the optimization process. To demonstrate the effectiveness of this work, we tested this technique in two case studies. To reach out to a wider range of users, we also developed a web application called Colourmap Hospital.

A Study on Glyph-based Visualisation with Dense Visual Context

In a focus+context visualization, one often finds it difficult to overlay focus information on top of a dense visual context. This work is motivated by a need for visualizing search results (i.e., focus) in relation to a treemap representation of a large file system (i.e., context). We thus consider that the focus consists of a collection of visual objects discretely-distributed over a background featuring dense context information. The conventional approach for showing such objects in focus is to use colored dots, which can encode limited information and may be difficult to discern from the context background. In this paper, we report a study on three alternative approaches, namely (a) cyclically-animated dot, (b) static glyph and (c) cyclically-animated glyph. We conducted a focus group study for qualitative evaluation and found that cyclically-animated dots and static glyphs are the preferred alternatives. While fine tuning cyclic animation is feasible, cyclically-animated glyphs do not offer an attractive solution in