Contributions published at Visualization and MultiMedia Lab (Renato Pajarola)

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In this paper we explore the algorithmic space in which stripification, simplification and geometric compression of triangulated 2-manifolds overlap. Edge-collapse/uncollapse based geometric simplification algorithms develop a hierarchy of collapses such that during uncollapse the reverse order has to be maintained. We show that restricting the simplification and refinement operations only to, what we call, the collapsible edges creates hierarchyless simplification in which the operations on one edge can be performed independent of those on another. Although only a restricted set of edges is used for simplification operations, we prove topological results to show that, with minor retriangulation, any triangulated 2-manifold can be reduced to either a single vertex or a single edge using the hierarchyless simplification, resulting in extreme simplification. The set of collapsible edges helps us analyze and relate the similarities between simplification, stripification and geometric compression algorithms. We show that the maximal set of collapsible edges implicitly describes a triangle strip representation of the original model. Further, these strips can be effortlessly maintained on multiresolution models obtained through any sequence of hierarchyless simplifications on these collapsible edges. Due to natural relationship between stripification and geometric compression, these multi-resolution models can also be efficiently compressed using traditional compression algorithms. We present algorithms to find the maximal set of collapsible edges and to reorganize these edges to get the minimum number of connected components of these edges. An order-independent simplification and refinement of these edges is achieved by our novel data structure and we show the results of our implementation of view-dependent, dynamic, hierarchyless simplification. We maintain a single triangle strip across all multi-resolution models created by the view-dependent simplification process. We present a new algorithm to compress the models using the triangle strips implicitly defined by the collapsible edges.

Security is a basic need of human beings. However, people in our society often do not attempt to achieve total security but are content with appropriate protection from major risks. The development of modern society has increasingly made this task the responsibility of the individual who can no longer rely on the social net formerly provided by big families. On the one hand, the development of technology, which has introduced new and hardly assessable risks, undermines people's sense of personal safety, on the other hand it offers new means to improve risk management. It is the objective of this book to show how individuals may identify, assess, and manage their risks in a systematic manner by means of a computer-based tool. To that intent, in the first part, the various aspects and definitions of the term "risk" will be discussed and then summarised in a comprehensive view of risk. Thus, the differing attitudes of individuals are taken into account. For instance, one person may consider risk to mean possible damage, another may think of a potential series of unfortunate circumstances with adverse effects, and yet another might associate the term with something that jeopardises the realisation of personal goals. Personal Risk Management (PRM) is only slightly different from the risk management of a company. The distinctive difference lies in the fact that companies, especially major ones, employ professional risk managers whereas most individuals, provided they consciously assess their risks at all, merely do so as an afterthought. Thus, PRM support of individuals not only has to adapt to one's particular understanding of what constitutes a risk, but also to the particular approach of dealing with it. A parent, for example, is likely to be interested in the risks facing his or her child in the future, whereas another individual primarily wants to find out whether it makes sense to take out a life insurance policy. However, in addition to supporting individuals in their specific approach, there should also be advice on how to optimise the procedure. Hence, a taxonomy of PRM approaches will be developed on the basis of a comprehensive view of PRM. In order to assess the risk that individuals face in a systematic and comprehensive way, a model of the individual will be presented. Physical, mental, financial and material aspects will be taken into consideration as well as the individual's social, economic, technological and ecological relationships within his or her environment. Furthermore, the human life cycle will be taken into account. The IT part of this book deals with the problem of how the elaborated concepts of PRM support can be transformed into a computer-based solution by means of modern approaches to software engineering. A system architecture will be presented. In order to realise it, the domain must be modelled accurately on the conceptual level. An objectoriented model meets this criterion by clearly representing the models that were outlined in words in the first part by means of Unified Modeling Language diagrams. The IT-implementation aspects will not only be discussed theoretically but a prototype with its emphasis on the goal-oriented approach will also be presented. An empirical study based on the prototype provides evidence for the fact that the suggested approach can be implemented.