Browsing by Author "Ware, Colin"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    3-D visualization of message passing in distributed programs
    (1996) Gobrecht, Cyril; Ware, Colin; Bhavsar, Virendrakumar, C.
    This paper describes PVMtrace, a software system for understanding and debugging message passing in distributed programs. In this system each process is represented as a node in a graph and the arcs represent the potential communication channels. The transfer of a packet of information from one process to another is shown by a bead-like object moving along an arc. A queue is a string of beads lined up waiting to be processed. The flexible control over time is found to be essential for the system to be useful and it allows the animation to be played forward and backwards in time both by the direct manipulation of the time line and by an animation rate controller. In addition there is an automatic time control method that rapidly moves the animation through intervals of low activity while slowing down in periods of high activity. The system was initially developed as a PVM debugging tool but it has also been found to be useful in other areas. In particular it has been used to visualize communications in a cellular phone system.
  • Thumbnail Image
    Item
    Perceving data displayed through oscillatory motion
    (1994) Ware, Colin; Limoges, Serge
    The idea of using simple sinusoidal motion of data points in a multidimensional scatter plot is explored both through a constructive analysis and by means of three experimental studies. In the system described, data values can be mapped to any combination of frequency, relative phase and amplitude as well as point size, point gray value and the center of motion. Three experiments assess the efficiency of the three motion parameters and the other display parameters in displaying correlations. The results of the first experiment suggest that relative phase is the most useful of the motion parameters, it compares favorably with gray value and point size, although it is not as effective as position on the vertical axis (the conventional scatter plot). The second and third experiments measure interference between display variables. The results show that motion does interfere with data represented by position and gray value but a phase representation is better in this respect than a frequency representation. It is argued that many natural phenomena result in related objects, or parts of objects moving in phase and this may be why relative phase is an effective display method.
  • Thumbnail Image
    Item
    Reaching for Objects in VR Displays: Lag and Frame Rate
    (1994) Ware, Colin; Balkrishnan, Ravin
    This paper reports the results from three experimental studies of reaching behavior in a head-coupled stereo display system with a hand tracking sub-system 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 difficulty. 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.
  • Thumbnail Image
    Item
    Visualizing information nets in three dimensions
    (1994) Ware, Colin; Frank, Glenn
    At present it is not clear if it is worth presenting abstract data in 3D, although there is a small body of evidence to support the idea. This paper reviews the evidence and reports on two new experiments that provide some compelling data showing that head coupled perspective transformations combined with stereo viewing can dramatically increase the size of the information structures that can be perceived. The first experiment was designed to provide the first 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 true 3D viewing can increase the size of the graph that can be understood by a factor of three; using stereo or head coupling alone produce lesser advantages. The second experiment looked at a variety of viewing methods, both 2D and 3D, with and without stereo, and with and without motion. The results show that structured 3D motion and stereo viewing both help in understanding, but that the kind of motion is not particularly important; hand guided motion, head coupling (as in virtual reality displays) and automatic rotation all improve performance. These results provide strong reasons for using advanced 3D graphics for interacting with a large variety of information structures.