Diagramming information structures using 3D perceptual primitives

The class of diagrams known collectively as node-link diagrams are used extensively for many applications, including planning, communications networks, and computer software. The defining features of these diagrams are nodes, represented by a circle or rectangle connected by links usually represented by some form of line or arrow. We investigate the proposition that drawing three-dimensional shaded elements instead of using simple lines and outlines will result in diagrams that are easier to interpret. A set of guidelines for such diagrams is derived from perception theory and these collectively define the concept of the geon diagram. We also introduce a new substructure identification task for evaluating diagrams and use it to test the effectiveness of geon diagrams. The results from five experiments are reported. In the first three experiments geon diagrams are compared to Unified Modeling Language (UML) diagrams. The results show that substructures can be identified in geon diagrams with approximately half the errors and significantly faster. The results also show that geon diagrams can be recalled much more reliably than structurally equivalent UML diagrams. In the final two experiments geon diagrams are compared with diagrams having the same outline but not constructed with shaded solids. This is designed to specifically test the importance of using 3D shaded primitives. The results also show that substructures can be identified much more accurately with shaded components than with 2D outline equivalents and remembered more reliably. Implications for the design of diagrams are discussed.