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Visualization - Technical Reports

Copies can be obtained by contacting the nearest IRIS Explorer Center, NAG office or NAG distributor.

Key

IETR/n - Report series number
(NPnnnn) - NAG Publication reference number

Index of Reports

Visualization For Public-Resource Climate Modeling
Jeremy Walton, Dave Frame and David Stainforth | IETR/13 (NP3661) PDF

Climateprediction.net aims to harness the spare CPU cycles of a million individual users' PCs to run a massive ensemble of climate simulations using an up-to-date, full-scale 3D atmosphere-ocean climate model. Although it has many similarities with other public-resource computing projects, it is distinguished by the complexity of its computational task, its system demands and the level of participant interaction, data volume and analysis procedures. For simulations running on individual PCs, there is a requirement for compelling visualizations that are readily grasped, since most users will be interested in the output from the model, but will have a limited level of scientific experience. This paper describes the design and implementation of these visualizations.

NAG's IRIS Explorer
Jeremy Walton | IETR/12 (NP3654) PDF

Data visualization can be defined as the gaining of insight by making a picture out of numbers, and the important role that it plays in the effective interpretation and analysis of numerical data has been recognized for a long time [1]. The type of data to be analyzed can vary from one-dimensional time series (e.g. yearly changes in salary) to multidimensional vector-based datasets (e.g. air flow over an airplane wing). Whilst the simpler types of data can be effectively displayed using ubiquitous desktop applications such as Excel, more complex data require more sophisticated visualization techniques and applications.

Putting You In The Picture: Enhancing Visualization With A Virtual Environment
David Boyd, Julian Gallop and Jeremy Walton | IETR/11 (NP3653) PDF

We describe recent work aimed at the integration of a visualization package and a virtual reality system, with the emphasis on the re-use and enhancement of commercially available products. The objective of the work is to determine what advantages (if any) are to be gained by combining the visualization package (which is well-suited for the conversion of numerical data into appropriate geometrical representations) with the comparatively novel immersive navigation methods of virtual reality. Our system|called VIVRE|was designed and built to meet the requirements of users who were to apply it to real industrial problems. They found that the use of the new navigation methods were advantageous for large datasets, and that direct interaction with elements of the visualization (for example, cutting planes) gave new insight into their data.

Implementing a statistical data type in IRIS Explorer
Patrick Craig | IETR/10 (NP3160) HTML or postscript

This paper is aimed at IRIS Explorer users who want to create their own data types. It is intended to be read in conjunction with the information given in the Creating User-defined Data Types chapter of the IRIS Explorer Module Writer's Guide. A new data type for handling statistical data is specified and the procedure for implementing and using the new type is described.

Rock `n' Roll: Using VRML 2.0 for Visualisation
IETR (NP3159) HTML or postscript

The Virtual Reality Modelling Language (VRML) is used to publish 3D scenes on the World Wide Web. In this paper, we give a brief account of the development of VRML and discuss its use in the context of scientific visualisation. We pay particular attention to the new features that have been added to the language at version 2.0, and assess these for their utility in sharing visualisations of complex 3D datasets. Chief among the new features is the ability to add behaviour to the scene, and we present a number of examples (garnered from our own work, and scenes which we have discovered on the Web) of dynamic visualisations which make use of these enhancements. Finally, we describe some of the shortcomings which we perceive in VRML 2.0, and indicate ways in which the language could usefully evolve in the future.

Data Visualisation with IRIS Explorer - What's New?
Walton, J. | IETR/8 (NP3070) postscript

The use of IRIS Explorer, a data visualisation toolkit, is described with reference to some examples from the fields of chemistry, computational fluid dynamics and finite element analysis. Some of the new features in the latest version of the toolkit are highlighted, and its relationship to other technologies such as the NAG Fortran 77 library, Open Inventor and VRML are discussed in detail.
Keywords: IRIS Explorer; Open Inventor; software re-use; VRML

Visualisation Benchmarking: A Practical Application of 3D Publishing
Walton, J. | IETR/7 (NP3069) postscript

How good is a visualisation? The current proliferation of software tools with their promise of the painless transformation of complex data sets into images or geometry can leave unanswered questions of reliability and accuracy. Benchmarking visualisation systems requires some way of comparing their results, but until recently these direct comparisons have been somewhat hampered by inconsistencies in the format used by the different systems to represent geometry. With the advent of VRML (and its more sophisticated precursor, Open Inventor) as a standard for 3D publishing and sharing on the WWW, these barriers have been removed. We illustrate this by directly comparing the results obtained from some visualisation systems when they are assigned the same task on the same piece of data. The results highlight some general principles concerning the importance of documentation of algorithms, and the benefits of a common language for 3D interchange.

See what I mean? Using Graphics Toolkits to Visualise Numerical Data
Walton, J. and Dewar, M. | IETR/6 (NP3068) postscript

The use of graphics toolkits to visualise and understand numerical data is explored with reference to (a) a common data format for 3D geometry and (b) the improvement of visualisation algorithms through the incorporation of numerical library software.

Using a common 3D format allows scenes and objects to be shared between applications and---if desired---published on the World-Wide Web (WWW) for viewing by co-workers elsewhere. Two examples of this are given. In one, we outline how the adoption of a standard toolkit to provide the visualisation component of a computer algebra package has cut down on development time and has provided it with the ability to share 3D data with other applications. In the other, we show how a graphics toolkit can be used within a visualisation web server, where its output can be transmitted across the WWW by means of the 3D format.

The use of library software can save the application developer time and effort in implementing fundamental algorithms, and allows them to concentrate on other aspects of the visualisation process. We describe some preliminary work on visualisation benchmarking, and show how some library routines are superior to simpler, but less sophisticated, algorithms in the context of particle tracing.

Publishing in a 3D World: Data Sharing with VRML
Walton, J. | IETR/5 (NP3067) postscript

The appearance of the Virtual Reality Modelling Language (VRML) as a standard for 3D interchange on the World Wide Web has had a number of benefits in the world of scientific visualisation. The ability to publish the results of a visualisation as a 3D object which can be manipulated by other workers in the field, rather than as a static 2D image has interesting implications, particularly when the results are complex objects such as a molecule, an isosurface, or a particle trace. In this paper, we illustrate some of the possibilities for scientific visualisation by presenting some examples created using IRIS Explorer, a popular data visualisation toolkit.

The HyperScribe Data Management Facility
Wright, H. | IETR/4 (NP2995) postscript

The extension of application builder toolkitsg to encompass the broader ideals of problem solving environments has for some time been a goal for researchers in the fields of visualization and scientific computation.

One limitation on these efforts has been a lack of data management facilities within visualization systems, a difficulty which has been viewed by some as inherent in the dataflow paradigm upon which such tools are based.

The HyperScribe mechanism, which draws on the recent successful project GRASPARC, seeks to address this deficiency in a straightforward and generic fashion. Using a point-and-click interface, the user can draw a visual representation of the course taken by their computational experiment and use this tog organise and retrieve solution data which has been generated. The implementation of HyperScribe as a module within the IRIS Explorer visualization environment is described and its use is demonstrated in the context of work to develop an integrated problem solving environment for computational chemistry.

Visualisation of Chemical Reaction Trajectories using IRIS Explorer
Wright, H. | IETR/3 (NP2785) postscript

Displaying the time-varying concentrations of species taking part in a given chemical reaction through modelling using ODEs.

Visualisation of sphere packs using a dataflow toolkit
Walton, J. | IETR/2 (NP2682)

We describe the construction of a simple application for the visualisation of sphere packs, with applications to molecular graphics. Our development environment is IRIS Explorer, one of the new generation of so-called dataflow toolkits. We emphasise particularly the way in which working in such an environment facilitates the design and construction process, paying especial attention to tools which aid the importing of data into the application, the design of the user interface, and the extension or modification of existing tools. Some examples of the use of the application in the field of molecular modelling are presented.

Now You See It --- Interactive visualisation of large datasets
Walton, J. | IETR/1 (NP2679) compressed

We briefly review existing techniques for the visualisation of numerical data, before describing those methods which appear to be most promising in the search for a modern solution to the problem of interpreting large, multidimensional datasets. There is a requirement for data display methods which are powerful, and yet easy to invoke, modify and extend. We discuss some products which are currently available in this field for the engineer, and illustrate their use with a number of examples, drawn from some recent work performed at NAG.