GIOTTO3D: A System for Visualizing Hierarchical Structures in 3D

The eeective visualization of hierarchical structures is an important problem in the area of advanced visual interfaces. Hierarchical structures occur in a wide variety of visualization applications, including WWW-A hierarchical structure can be formally modeled by a directed acyclic graphs (DAG), i.e., a directed graph with no directed cycles. Hence, throughout this abstract, we will use the two terms interchangeably. Also we will use the terms visualization, drawing, layout and representation to denote the same concept. Hierarchical structures are usually visualized using hierarchical drawings. A hierarchical drawing is one in which each edge is drawn as a curve monotonically nondecreasing in the y-direction for 2D drawings and in the z-direction for 3D drawings. Three dimensions ooer many advantages over two dimensions for visualizing hierarchical structures. The extra dimension gives a greater exibility for placing the nodes and edges of the graph. The presence of navigational operations such as rotation, translation, and zooming not only helps the user in understanding the structure, but also results in a more eeective use of screen space because not every object has to be shown in front on the screen (as is the case with 2D-visualization). Many virtual-reality packages also accept descriptions of 3D layouts produced by other graphics packages. Research in graph drawing has generally concentrated on constructing two-dimensional visualizations because of the two-dimensional geometry of display surfaces such as paper and computer screen. Recent advances in hardware and software technology for computer graphics open the possibility of displaying three-dimensional (3D) visualizations on a variety of low-cost workstations, and several researchers (and lm makers y) have begun to explore the possibility of displaying graphs and networks using this new technology. Indeed, it is expected that in the next few years, 3D visualization will become widespread in Web documents , thanks to the VRML language for modeling three-dimensional scene graphs. Recent work on WWW navigation 14], software visualization 15], information visualization 16], and algorithm animation 1] has also advocated the use of 3D visual representations. Much work needs to be done on both theoretical and practical aspects of 3D hierarachical graph drawing. We now review some systems that construct 3D hierarachical graph drawings. The systems GMB 10] and PLUM 15] extend to 3D the layering approach 17, 6, 12] which was conceived for constructing two-dimensional hierarchical drawings. The drawings constructed by them have characteristics similar to their two-dimensional counterparts. In a cone tree 16], each …