This paper concerns the benefits of presenting abstract data in 3D. Two experiments show that motion cues combined with stereo viewing can substantially increase the size of the graph that can be perceived. The first experiment was designed to provide quantitative measurements of how much more (or less) can be understood in 3D than in 2D. The 3D display used was configured so that the image on the monitor was coupled to the user's actual eye positions (and it was updated in real-time as the user moved) as well as being in stereo. Thus the effect was like a local "virtual reality" display located in the vicinity of the computer monitor. The results from this study show that head-coupled stereo viewing can increase the size of an abstract graph that can be understood by a factor of three; using stereo alone provided an increase by a factor of 1.6 and head coupling alone produced an increase by a factor of 2.2. The second experiment examined a variety of motion cues provided by head coupled perspective (as in virtual reality displays), hand guided motion and automatic rotation respectively, both with and without stereo in each case,. The results show that structured 3D motion and stereo viewing both help in understanding, but that the kind of motion is not particularly important; all improve performance, and all are more significant than stereo cues. These results provide strong reasons for using advanced 3D graphics for interacting with a large variety of information structures.

The sources of lag (the delay between input action and output response) and its effects on human performance are discussed.We measured the effects in a study of target acquisition using the classic Fitts' law paradigm with the addition of four lag conditions.At the highest lag tested (225 ins), movement times and error rates increased by 64% and 21490 respective y, compared to the zero lag condition. We propose a model according to which lag should have a multiplicative effect on Fitts' index of difficulty. The model accounts for 9470 of the variance and is better than alternative models which propose only an additive effect for lag.The implications for the design of virtual rerdity systems are discussed.

A large class of diagrams can be informally characterized as node–link diagrams. Typically nodes represent entities, and links represent relationships between them. The discipline of graph drawing is concerned with methods for drawing abstract versions of such diagrams. At the foundation of the discipline are a set of graph aesthetics (rules for graph layout) that, it is assumed, will produce graphs that can be clearly understood. Examples of aesthetics include minimizing edge crossings and minimizing the sum of the lengths of the edges. However, with a few notable exceptions, these aesthetics are taken as axiomatic, and have not been empirically tested. We argue that human pattern perception can tell us much that is relevant to the study of graph aesthetics including providing a more detailed understanding of aesthetics and suggesting new ones. In particular, we find the importance of good continuity (ie keeping multi-edge paths as straight as possible) has been neglected. We introduce a methodology for evaluating the cognitive cost of graph aesthetics and we apply it to the task of finding the shortest paths in spring layout graphs. The results suggest that after the length of the path the two most important factors are continuity and edge crossings, and we provide cognitive cost estimates for these parameters. Another important factor is the number of branches emanating from nodes on the path.

Pseudocoloring is a widely used technique for presenting univariate map information on a graphic display system. This article divides the kinds of information available in maps into two classes. Metric (or value) information denotes the quantity stored at each point on the surface, and form information denotes the shape and structure of the surface. Theoretical principles are proposed to predict which color sequences will be effective at conveying value and form information respectively. According to this theory a scale that approximates the physical spectrum should be good at conveying metric information because of the reduced effects of simultaneous contrast. It should be poor at conveying form information, however, because the brain prefers from information to come through the lightness processing "luminance" channel. Conversely, a gray scale should be poor at conveying value information and good at conveying form information according to the same theory.These predictions are tested in a series of psychophysical experiment which test five color sequences. The results show that simultaneous contrast can be a major source of error when reading maps, but only partially confirm the form hypothesis. Guidelines are given, based on the theory, for designing color sequences to be effective in both conveying form and value information. An experimental color sequence is presented to illustrate these guidelines.

This article reports the results from three experimental studies of reaching behavior in a head-coupled stereo display system with a hand-tracking subsystem for object selection. It is found that lag in the head-tracking system is relatively unimportant in predicting performance, whereas lag in the hand-tracking system is critical. The effect of hand lag can be modeled by means of a variation on Fitts' Law with the measured system lag introduced as a multiplicative variable to the Fitts' Law index of difilculty. This means that relatively small lags can cause considerable degradation in performance if the targets are small. Another finding is that errors are higher for movement in and out of the screen, as compared to movements in the plane of the screen, and there is a small (10'%) time penalty for movement in the Z direction in all three experiments. Low frame rates cause a degradation in performance; however, this can be attributed to the lag which is caused by low frame rates, particularly if double buffering is used combined with early sampling of the hand-tracking device.