Jeremy Walton

Distributed and Collaborative Visualization

Visualization is a powerful tool for analyzing data and presenting results in science, engineering and medicine. This paper reviews ways in which it can be used in distributed and/or collaborative environments. Distributed visualization addresses a number of resource allocation problems, including the location of processing close to data for the minimization of data traffic. The advent of the Grid Computing paradigm and the link to Web Services provides fresh challenges and opportunities for distributed visualization—including the close coupling of simulations and visualizations in a steering environment. Recent developments in collaboration have seen the growth of specialized facilities (such as Access Grid) which have supplemented traditional desktop video conferencing using the Internet and multicast communications. Collaboration allows multiple users—possibly at remote sites—to take part in the visualization process at levels which range from the viewing of images to the shared control of the visualization methods. In this review, we present a model framework for distributed and collaborative visualization and assess a selection of visualization systems and frameworks for their use in a distributed or collaborative environment. We also discuss some examples of enabling technology and review recent work from research projects in this field.

Visualization in Grid Computing Environments

Grid computing provides a challenge for visualization system designers. In this research, we evolve the dataflow concept to allow parts of the visualization process to be executed remotely in a secure and seamless manner. We see dataflow at three levels: an abstract specification of the intent of the visualization; a binding of these abstract modules to a specific software system; and then a binding of software to processing and other resources. We develop an XML application capable of describing visualization at the three levels. To complement this, we have implemented an extension to a popular visualization system, IRIS Explorer, which allows modules in a dataflow pipeline to run on a set of grid resources. For computational steering applications, we have developed a library that allows a visualization system front-end to connect to a simulation running remotely on a grid resource. We demonstrate the work in two applications: the dispersion of a pollutant under different wind conditions; and the solution of a challenging numerical problem in elastohydrodynamic lubrication.

A Web Services Architecture for Visualization

Service-oriented architectures are increasingly being used as the architectural style for creating large distributed computer applications. This paper examines the provision of visualization as a service that can be made available to application designers in order to combine with other services. We develop a three-layer architecture: a client layer which provides the user interface; a stateful Web service middleware layer which provides a published interface to the visualization system; and finally, a visualization component layer which provides the core functionality of visualization techniques. This separation of middleware from the visualization components is crucial: it allows us to exploit the strengths of Web service technologies in providing standardized access to the system, and in maintaining state information throughout a session, but also gives us the freedom to build our visualization layer in an efficient and flexible way without the constraints of Web service protocols. We describe the design of a visualization service based on this architecture, and illustrate one aspect of the work by re-visiting an early example of Web-based visualization.

32 NAG's IRIS Explorer

This chapter introduces IRIS Explorer as a modular data-visualization system. The chapter describes the architecture of IRIS and some of its features and indicates the ways in which the modular architecture of IRIS leads to applications in which the constituent modules may be distributed, compiled together, or made collaborative. Users of IRIS Explorer create applications by selecting and connecting software modules via a visual programming interface. Each module is a routine that operates on its input data to produce some output. Although the module suite provided with IRIS explorer is extensive, users will eventually need new modules. This may be because they have existing code that they wish to incorporate into an IRIS Explorer map or because no module exists with the functionality that they require. The modular nature of the environment makes it easy to add the missing pieces of their application, using the tools that are bundled with the IRIS Explorer system. The chapter also discusses some of the software that underlies the system and has selected a few user applications in diverse fields. Finally, the chapter indicates how the basic visualization reference model that forms the basis of this system can be extended to collaborative steering on the grid and gives an account of the work that has moved IRIS Explorer in this direction.

An integrated visualization and design toolkit for flexible prosthetic heart valves

We describe a toolkit for the design and visualization of flexible artificial heart valves. The toolkit consists of interlinked modules with a visual programming interface. The user of the toolkit can set the initial geometry and material properties of the valve leaflet, solve for the flexing of the leaflet and the flow of blood around it, and display the results using the visualization capabilities of the toolkit. The interactive nature of our environment is highlighted by the fact that changes in leaflet properties are immediately reflected in the flow field and response of the leaflet. Hence the user may, in a single session, investigate a broad range of designs, each one of which provides important information about the blood flow and motion of the valve during the cardiac cycle.

See what I mean? Using graphics toolkits to visualise numerical data

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.

Visualization of sphere packs using a dataflow toolkit

We describe the construction of a simple application for the visualization 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 emphasize particularly the way in which working in such an environment facilitates the design and construction process, paying special 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 modeling are presented.