Configuring Hierarchical Layouts to Address Research Questions

We explore the effects of selecting alternative layouts in hierarchical displays that show multiple aspects of large multivariate datasets, including spatial and temporal characteristics. Hierarchical displays of this type condition a dataset by multiple discrete variable values, creating nested graphical summaries of the resulting subsets in which size, shape and colour can be used to show subset properties. These 'small multiples' are ordered by the conditioning variable values and are laid out hierarchically using dimensional stacking. Crucially, we consider the use of different layouts at different hierarchical levels, so that the coordinates of the plane can be used more effectively to draw attention to trends and anomalies in the data. We argue that these layouts should be informed by the type of conditioning variable and by the research question being explored. We focus on space-filling rectangular layouts that provide data-dense and rich overviews of data to address research questions posed in our exploratory analysis of spatial and temporal aspects of property sales in London. We develop a notation ('HiVE') that describes visualisation and layout states and provides reconfiguration operators, demonstrate its use for reconfiguring layouts to pursue research questions and provide guidelines for this process. We demonstrate how layouts can be related through animated transitions to reduce the cognitive load associated with their reconfiguration whilst supporting the exploratory process.     

Low‐Cost Subpixel Rendering for Diverse Displays

Subpixel rendering increases the apparent display resolution by taking into account the subpixel structure of a given display. In essence, each subpixel is addressed individually, allowing the underlying signal to be sampled more densely. Unfortunately, naïve subpixel sampling introduces colour aliasing, as each subpixel only displays a specific colour (usually R, G and B subpixels are used). As previous work has shown, chromatic aliasing can be reduced significantly by taking the sensitivity of the human visual system into account. In this work, we find optimal filters for subpixel rendering for a diverse set of 1D and 2D subpixel layout patterns. We demonstrate that these optimal filters can be approximated well with analytical functions. We incorporate our filters into GPU‐based multi‐sample anti‐aliasing to yield subpixel rendering at a very low cost (1–2 ms filtering time at HD resolution). We also show that texture filtering can be adapted to perform efficient subpixel rendering. Finally, we analyse the findings of a user study we performed, which underpins the increased visual fidelity that can be achieved for diverse display layouts, by using our optimal filters.     

Facilities layout—A survey of solution procedures

The main characteristics of the most-used solution procedures for the facility layout problem are summarized. The characteristics include input required, limitations, type of output obtained, and some other general characteristics. Quantitative and computer-based models will sometimes produce odd layout shapes. For this reason, optimization models and computer prorams designed to plan facility layouts, based on optimizing certain objectives, can be useful only for determining some guidelines for the planners. While these models can be used for planning alternative layouts, considerations of qualitative and personnel factors should be given during the layout finalization phase.     

A technique for generating natural colour images from false colour composite images

Colour is widely used in remote sensing work. In many instances, the use of colour conveys additional information both visually and scientifically. Remote sensing satellites view the earth in different spectral bands, viz. near infrared (NIR), red, green, and blue bands, in a conventional multispectral imaging system. In the absence of a blue channel, colour images can be generated using near infrared, red, and green bands in what is known as a false colour composite (FCC) and does not look natural, like the image we see with the naked eye. For a trained interpreter, this does not pose any problems. However, when the intended use is a fly‐through of a draped terrain, visual interpretation, or a display, meant for the non‐remote sensing professional, this becomes a handicap. To overcome this, there is a requirement to generate natural colour composites (NCC) from the given false colour composite, which demands the simulation of a blue band to be combined with green and red bands. This paper describes a unique method of generating a blue band to form natural colour images from a given false colour image set. We use a spectral transformation method to establish a relationship between the false colour and true colour image pairs provided by a sensor with all the four bands, which has a broader spectral coverage. A transformation function is fitted by selecting radiometric control points along the line of geometric registration to find a set of coefficients to be used for simulating a blue band. This blue band, along with the green and red bands, provides a near true colour or ‘natural colour’ on the display. In this paper, we present a set of adjustable radiometric transformation coefficients to accommodate variation in spatial and dynamic range offered by sensors to generate natural colour. These coefficients seem to work on a large number of images of different seasons, provided similar spectral bands and terrain are used. The proposed ‘natural colour generator’ can be used in changing false colour images to natural colour images with the aim of ‘what you get is what you would have seen’.     

Visualization and User-Modeling for Browsing Personal Photo Libraries

We present a user-centric system for visualization and layout for content-based image retrieval. Image features (visual and/or semantic) are used to display retrievals as thumbnails in a 2-D spatial layout or “configuration” which conveys all pair-wise mutual similarities. A graphical optimization technique is used to provide maximally uncluttered and informative layouts. Moreover, a novel subspace feature weighting technique can be used to modify 2-D layouts in a variety of context-dependent ways. An efficient computational technique for subspace weighting and re-estimation leads to a simple user-modeling framework whereby the system can learn to display query results based on layout examples (or relevance feedback) provided by the user. The resulting retrieval, browsing and visualization can adapt to the user's (time-varying) notions of content, context and preferences in style and interactive navigation. Monte Carlo simulations with machine-generated layouts as well as pilot user studies have demonstrated the ability of this framework to model or “mimic” users, by automatically generating layouts according to their preferences.     

The effect of text and background colour on visual search of Web pages

Usability and visual impact in Web pages are not necessarily compatible ideals. This paper investigates the effect of colour on the presentation of information in a navigation bar, and aims to contribute towards design guidelines for the use of colour on the Web. We studied the effect of the combination of text and background colour on visual search performance and subjective preference. Twenty-nine participants carried out a visual search task using mock Web pages. Analysis showed that higher contrasts between text and background colour led to faster searching and were rated more favourably. The results are discussed in terms of visual search processes and design recommendations are given.     

Limits of visual perception in the technology of visual display terminals

. The limits of visual perception in present VDT technology for man-machine communication are considered. Essentially, these limits concern the reading of the displayed information and follow from the prevailing display conditions as to (i) luminous contrast, (ii) character shape, (iii) text layout and (iv) text colour. The effect of these conditions on legibility is quantitatively described from research results, and practical suggestions are given for improving display legibility, through changes in contrast polarity, character shape, layout and the way colour is used. Finally, a plea is made for including experts in visual ergonomics in the teams developing new display devices in the future.     

Colour for air traffic control displays

Air traffic controllers of the future will be working with full-colour raster-scan displays. This paper describes an approach to the use of colour whereby the objects on the display are assigned to a series of conceptual layers which are in turn represented as visual layers. Background map features are shown as opaque infills, overlaid with transparent infills for overlapping areas; alphanumeric labels in the foreground are shown in black, each with an attached infill to ensure good legibility and effective colour coding. Colour palettes are provided for each layer so that the display designer has flexibility but can be confident that the display will be free of colour illusions and ambiguities. The resulting displays can be used in normal office lighting. The work was undertaken for the Chief Scientist's Division of the National Air Traffic Services (part of the UK Civil Aviation Authority).     

Colour design in aviation cartography

The use of colour in maps from the earliest times to the present day is reviewed, and that experience is applied to the problems of airborne map displays. Studies of the priorities of various kinds of map information have been carried out. A set of principles and guidelines for the best use of colour in airborne map displays is given.     

On the evaluation of AGVS-based warehouse operation performance

An automated guided vehicle system (AGVS) is an advanced material handling system widely used in various automated systems, particularly in e-commerce warehouses. The warehouse operation performance, mainly focusing on transportation efficiency, is affected by many factors, such as traffic-control policies and warehouse layouts. Based on the digraph theory and real-time control, two effective traffic-control policies with polynomial-time complexity are proposed to avoid the collision and to solve deadlocks. To accommodate more complicated situations, different types of warehouse layouts are tested. Extensive simulations are carried out to study the effects of policies, warehouse layouts, task densities and timing of an AGV to apply for a resource on the evaluation of the AGVS-based warehouse operation performance, which provide guidelines for warehouse designers.     

Coding techniques for process plant VDU formats

The results of a literature survey of human performance and coding techniques are presented. Recommendations are given for the application of coding techniques to the design of VDU formats (screen layouts) in a process plant context. The coding techniques considered are colour, brightness, inverse video, flash, size and shape. The recommendations discuss the relative merits of the different techniques for presenting plant information, and the practical problems of applying a particular code. Some suggestions are given for further work.     

Performance evaluation of multi‐primary color‐matrix layouts for mobile displays

Abstract— Different subpixel layouts for multi‐primary displays will be presented and their spatial performance analyzed. The layouts studied include red, green, blue, yellow, and cyan subpixels, arranged in 5/5, 5/4, and 5/3 configurations. In the 5/5 configuration, five primaries are arranged on five subpixels forming a square pixel. In the 5/4 configuration, five primaries are arranged on two square units, each of which have four subpixels so that the cyan and yellow subpixels are missing in alternate pixels. In the 5/3 layout, the multi‐primary color matrix is placed on top of a standard RGB TFT backplane with a subpixel aspect ratio of 1:3, resulting in an increased period of the full color sequence. Different data‐rendering methods for the modified color sequences were studied and their implication on the spatial performance were analyzed, given in terms of reproduction accuracy, i.e., the average S‐CIELAB error between data reproduced on a reference display and that reproduced on the examined layout. The reproduction error as a function of the angular substance of a pixel is reported for different layouts and rendering methods and are compared to that of an RGB display. It will be shown that the modified multi‐primary layouts reduce power consumption and provide good image quality for mobile applications.     

Calculating the perceptibility of monochrome and colour displays viewed under various illumination conditions

Results from a series of calculations which assist the display designer to assess the optimum colour or colours for use on a display device are presented. Plots are produced which indicate the principles which must be adopted in the evaluation of the relative importance of display luminance and colour when the device is to be viewed under both specific and widely differing illumination conditions.     

Colour in map displays: issues for task-specific display design

Colour is generally regarded as a desirable property of computer displays chiefly because it supports users' preattentive visual processes, such as texture segregation, which rapidly organize and structure screen information. This paper examines the use of colour in computerized map displays of the sort used by geographic information systems. In particular, it focuses on the perception of patterns formed by subclasses of map symbols, defined by colour or shape. Three experiments are reported which confirm the utility of colour, but which also identify two potential problems: interference of task-irrelevant colour and superficial processing of spatial configurations of colour-defined symbols. These findings support a general argument that colour should not be preferred automatically, but rather its utility depends on the cognitive demands of the task for which the display is designed.     

Colour size illusion on liquid crystal displays and design guidelines for bioinformatics tools

Although the influence of colour on size perception has been known for a century, there is only limited research on interventions that can reduce this effect. This study was therefore undertaken in order to identify appropriate interventions and propose design guidelines for information visualisation, especially in applications where size judgement is critical. The colour size illusion was replicated on an LCD monitor, revealing that yellow images appeared the smallest among a series of red, yellow, green and blue images on a white background. Three types of interventions (background brightness, border colour and background grid brightness) were tested to identify conditions that reduce the colour illusions, but none proved to be statistically significant. Based on these experimental results and an extensive literature survey, a set of design guidelines is proposed to enhance the usability of LCD monitors and a set of design recommendations given to extend these guidelines to applications in the field of bioinformatics. These design recommendations are accompanied by an evaluation of effectiveness obtained by interviewing domain experts.     

ICA-based fusion for colour display of hyperspectral images

Hyperspectral images contain data from a large number of contiguous bands and, therefore, cannot be displayed directly using a colour display system. In this paper, an independent component analysis-based (ICA-based) approach for the problem of fusing hyperspectral images to three-band images for colour display purposes is proposed. Correlation coefficient and mutual information (ICA-CCMI) are used as criteria for selecting three suitable independent components for colour representation. In addition, statistical evaluation metrics for the colour display results of hyperspectral images are provided and discussed in light of different visualization goals. A new quality metric motivated by the quality index is developed to evaluate the structural information of the colour display images. The performance of our approach is validated by applying it to three hyperspectral image datasets. The experimental results demonstrate promising performance for the ICA-CCMI algorithm, compared with existing principal component analysis-based (PCA-based) methods for visualization of hyperspectral images.     

A Comparison of User-Generated and Automatic Graph Layouts

The research presented in this paper compares user-generated and automatic graph layouts. Following the methods suggested by van Ham et al. (2008), a group of users generated graph layouts using both multi-touch interaction on a tabletop display and mouse interaction on a desktop computer. Users were asked to optimize their layout for aesthetics and analytical tasks with a social network. We discuss characteristics of the user-generated layouts and interaction methods employed by users in this process. We then report on a web-based study to compare these layouts with the output of popular automatic layout algorithms. Our results demonstrate that the best of the user-generated layouts performed as well as or better than the physics-based layout. Orthogonal and circular automatic layouts were found to be considerably less effective than either the physics-based layout or the best of the user-generated layouts. We highlight several attributes of the various layouts that led to high accuracy and improved task completion time, as well as aspects in which traditional automatic layout methods were unsuccessful for our tasks.     

Mesh layouts for block-based caches

Current computer architectures employ caching to improve the performance of a wide variety of applications. One of the main characteristics of such cache schemes is the use of block fetching whenever an uncached data element is accessed. To maximize the benefit of the block fetching mechanism, we present novel cache-aware and cache-oblivious layouts of surface and volume meshes that improve the performance of interactive visualization and geometric processing algorithms. Based on a general I/O model, we derive new cache-aware and cache-oblivious metrics that have high correlations with the number of cache misses when accessing a mesh. In addition to guiding the layout process, our metrics can be used to quantify the quality of a layout, e.g. for comparing different layouts of the same mesh and for determining whether a given layout is amenable to significant improvement. We show that layouts of unstructured meshes optimized for our metrics result in improvements over conventional layouts in the performance of visualization applications such as isosurface extraction and view-dependent rendering. Moreover, we improve upon recent cache-oblivious mesh layouts in terms of performance, applicability, and accuracy.     

Evaluation of traditional, orthogonal, and radial tree diagrams by an eye tracking study

Node-link diagrams are an effective and popular visualization approach for depicting hierarchical structures and for showing parent-child relationships. In this paper, we present the results of an eye tracking experiment investigating traditional, orthogonal, and radial node-link tree layouts as a piece of empirical basis for choosing between those layouts. Eye tracking was used to identify visual exploration behaviors of participants that were asked to solve a typical hierarchy exploration task by inspecting a static tree diagram: finding the least common ancestor of a given set of marked leaf nodes. To uncover exploration strategies, we examined fixation points, duration, and saccades of participants' gaze trajectories. For the non-radial diagrams, we additionally investigated the effect of diagram orientation by switching the position of the root node to each of the four main orientations. We also recorded and analyzed correctness of answers as well as completion times in addition to the eye movement data. We found out that traditional and orthogonal tree layouts significantly outperform radial tree layouts for the given task. Furthermore, by applying trajectory analysis techniques we uncovered that participants cross-checked their task solution more often in the radial than in the non-radial layouts.     

The effects of ambient illumination and target luminance on colour coding in a CRT display

In this paper, the effects of absolute colour-identification on a CRT display are compared under different experimental conditions, i.e., ambient illuminant intensity, colour temperature and target luminance. The results indicate that performance of colour identification deteriorated as ambient illuminant intensity was increased. Colour identification under the 2800 K colour temperature was better than that under the 1800 K and 5800K. Performance at high luminance was superior to that at low luminance. Colours were chosen to make up the colour coding system on the CRT display under various ambient illuminant conditions. The number and range of the colours selected for the colour coding could be expanded by increasing the target luminance on the CRT display.