PhD Thesis - staffweb - University of Greenwich

PhD Thesis by John Ewer.4.2.2 HCI design issuesThere were two distinct choices for the User Interface (UI) paradigm that could be used withthe prototype CFD system.4.2.2.1 Visual programming interfaceA visual programming interface would use visual icons and links to represent data passingthrough and being modified by the system. Generally the tools could be "opened" and have theirbehaviour modified using a tool specific menu. Such interfaces have become quite common forimage processing systems and, to a lesser extent, for visualisation systems. The problem witha visual programming paradigm for CFD is that it would be inappropriate to the experience ofmany users. There are often quite high initial learning overheads for visual systems but once thenature of the interface has been learnt then new components and tools are usually quite easy touse. It is generally quite difficult to implement visual interfaces in a portable way and allapplication tools have to be available and accessible from the interface. There is large scope forinappropriate configuration unless great care is taken for the component linking strategy. It islikely that a CFD visual programming interface would quickly become cluttered with tools andfilters due to the complexity of the underlying numerical system and the potential formodifications to that architecture. There are currently very few examples of applications that usethe visual programming metaphor so it was difficult to assess the potential effectiveness of thisparadigm. Generally visual programming seems to be a very powerful tool when datatransformations through a system can be conceived as a linked list of filters and transformationtools (E.g. AVS, Khouros) but the nature of the CFD system suggested that this type ofinterface be avoided. It is not simple to conceive of one, or more, simple data pipelines becauseof the complex data interdependencies inherent in CFD computations. A well designed visualprogramming interface would be a powerful tool for an expert CFD user or a CFD developerbut most users would probably never use the majority of the capabilities of the interface and,furthermore, are likely to be confused to such an extent that in-appropriate linkages are formedthat break the software.4-74