B. Watson, V. Spaulding, N. Walker, and W. Ribarsky. Evaluation of the Effects of Frame Time Variation on VR Task Performance. In Proceedings of the Virtual Reality Annual International Symposium, page 38, 1997.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....to create immersion. It s been proven that virtual reality tasks require a high frame rate, about 20 frames per second (fps) to maintain interactivity, and they are sensitive to frame rate variations. Any frame rate variation of more than 10 begins to interfere with the users ability to interact [8]. Martin Reddy observed that level of detail (LOD) algorithms didn t seem to be propagating into the virtual reality industry as fast as in other industries. He tested several commercial packages and found that while most packages supported programmer implemented distance based LOD, only three ....

Benjamin Watson, Victoria Spaulding, Neff Walker, and William Ribarsky. Evaluation of the Effects of Frame Time Variation on VR Task Performance. In Proc. IEEE Virtual Reality Annual Symposium, pages 38-44, April 1997.

....In this case, we would only want to trade off latency, which affect the user s perceived system responsiveness, to improve frame rate if the latency remains under an acceptable threshold. While this threshold is subjective, 100 ms is typically accepted as a reasonable upper bound (e.g. see [1, 19]) This implies that we should not overlap communication with computation until we can achieve at least 10 15 fps (15 because multi threading can increase latency as much as 58 ) which is already at the boundary of interactivity. Beyond this, overlapping com munication with computation can help ....

B. Watson, V. Spaulding, N. Walker, and W. Ribarsky. Evaluation of the Effects of Frame Time Variation on VR Task Performance. Technical Report 96-17, Georgia Institute of Technology, Graphics, Visualization, and Usability Center, 1997.

....a certain threshold. This threshold can be specified by users according to different application requirements. Maintaining a constant frame rate is also very important. Especially when the mean frame time is high, fluctuations in frame rate can influence the performance of interactive 3D tasks[16]. We test both of the above targets, threshold and consistency. First we specify a frame rate and test the algorithm to see if it can always keep the frame rate above this threshold. Secondly, we record the frame time and calculate the mean fluctuation F with respect to the mean frame time # f ....

Benjamin Watson, Victoria Spaulding, Neff Walker, and William Ribarsky. Evaluation of the Effects of Frame Time Variation on VR Task Performance . Technical report, Georgia Institute of Technology, 1996.

....Otherwise, we would only want to trade off latency, which affect the user s perceived system responsiveness, to improve frame rate if the latency remains under an acceptable threshold. While this threshold is subjective, 100 ms is typically accepted as a reasonable upper bound (e.g. see [2, 21]) This implies that we should not overlap communication with computation until we can achieve at least 10 15 fps (15 because multi threading can increase latency as much as 58 ) which is already at the boundary of interactivity. Beyond this, overlapping communication with computation can help ....

B. Watson, V. Spaulding, N. Walker, and W. Ribarsky. Evaluation of the Effects of Frame Time Variation on VR Task Performance. Technical Report 96-17, Georgia Institute of Technology, Graphics, Visualization, and Usability Center, 1997.

....Another area of current research is the effect of various low level system characteristics on performance in immersive VEs. Besides the studies addressing display type mentioned earlier, there have been experiments on the effect of mean frame rate (Richard et al., 1995) variance of frame rate (Watson et al., 1997), and level of visual detail (Watson, Walker, and Hodges, 1995) These experiments have generally used a standard task, such as visual search or pick and place, and compared users speed and accuracy under the various experimental conditions. Such studies are similar in format to those we will ....

Watson, B., Spaulding, V., Walker, N., and Ribarsky, R. (1997). Evaluation of the Effects of Frame Time Variation on VR Task Performance. Proceedings of the IEEE Virtual Reality Annual International Symposium, 1997, 38-44.

....3D user interfaces, we are not aware of any formal studies that evaluate and categorize interaction techniques and metaphors for picking and positioning of objects in VEs. Prior research relates primarily to user performance as affected by various input and output devices and their characteristics [8, 9]. In contrast, the focus of this study is on the human factors characteristics of different mappings between user input, captured by input devices, and resulting actions in VEs i.e. interaction techniques [3] RELATED WORK Object selection and positioning are among the most fundamental ....

....isotonic for position control. Studies of stereoscopic versus monoscopic displays suggest that stereoscopy improves performance for complex manipulation tasks [13] The effects of system performance characteristics (such as lag and frame rate) on user manipulation performance has also been studied [9, 14]. Investigation of the human factors of input and output devices has considerable value; however, the lack of systematic research on manipulation interaction techniques, which map the user s actions captured by input devices into re sulting actions in VE [3] can significantly limit their ....

Watson, B., V. Spaulding, N. Walker, and W. Ribarsky, Evaluation of the effects of frame time variation on VR task performance. Proceedings of VRAIS'96. 1996. IEEE. pp. 38-52.

....and transport delay on the user s ability to perform a particular tracking task was quantitatively similar) For example, Tharp et al. 1992) found that performance degraded below 10 Hz for their immersive tracking experiments, and that performance levels reached a plateau between 10 20 Hz. Also, Watson et al. 1997) report that moving from a frame rate of 20 Hz down to 10 Hz significantly degraded user performance, both in terms of accuracy and response time. 2 Goal of Current Study In this report we are concerned solely with the effect of frame rate on the ability of users to perform a prescribed task in a ....

....but we also make the addendum that higher frame rates will continue to improve performance and should be strived for in performance critical applications. The results from this study compare favourably with those found by other researchers using different approaches (e.g. Tharp et al. 1992; Watson et al. 1997). It is also worth noting that Barfield and Hendrix (1995) report that frame rates of less than 15 Hz can significantly diminish a user s sense of presence within a VE. It would therefore appear that their level of presence results correlate well with our task performance results. ....

Watson, B., Spaulding, V., Walker, N. and Ribarsky, W. (1997). Evaluation of the Effects of Frame Time Variation on VR Task Performance, Technical Report GIT--GVU--9617, Graphics, Visualization and Usability Centre, Georgia Institute of Technology, Atlanta, GA.

....versus isotonic devices for different conditions of spatial manipulation. Other studies focused on the influence of output device characteristics on user manipulation performance. Nemire [31] for example, studied the effect of visual and aural enhancement on the user s manipulation; Watson et al. [25] studied the effects of frame time variation on tracking and placing task performance. However, it is not only input and output devices and their characteristics that matter: different interaction techniques allow users to accomplish tasks in different ways using the same input devices [2, 27] ....

....of hand movements during the reaching positioning of the object. Measurement of user to object distances, virtual cubits Most of the current studies of human factors in VR use either real world units of measurements, such as meters, or computer graphics units, such as points (for example, see [8, 25]) However, are these the best units for studying immersive manipulation One argument for using real world units is the user s familiarity with them. However, because perception of distances and sizes in VR differs from the real world [33] users cannot reliably transfer their real world spatial ....

Watson, B., Spaulding, V., Walker, N., Ribarsky W. Evaluation of the effects of frame time variation on VR task performance. IEEE VRAIS'96, 1996, pp. 38-52

....SR is made up of system latency as well as the additional time between the Human Factors, Special Section on Virtual Environments, 40, 3 (Sept) 403 414 4 completion of a user action and the next input sample used in display. More detailed discussions of the elements of SR can be found in (Watson, 1997), Wloka, 1995) and (Mine, 1993) Figure 1 about here The terms system latency and SR are often used interchangeably, referring at times to the age of a sample, and at other times to the delay until feedback is received. This is unfortunate and can lead to much ....

....sensitive to SDSR. However, SDSR must be quite severe before it affects user performance. This suggests control of SDSR can be quite loose. Our research indicates that posing SDSR control in percentage of mean frame rate is more effective than control in absolute frame rate terms. In related work (Watson, Spaulding, Walker Ribarsky, 1997), symmetric fluctuation of SR had less effect than the fluctuation in this study, which was biased to longer SR. This suggests that transient improvements in SR should be of little concern to system designers; transient worsening of SR is more harmful to user performance. There are a number of ....

Watson, B., Spaulding, V., Walker, N. & Ribarsky, W. (1997). Evaluation of the effects of frame time variation on VR task performance. In Proceedings of the Virtual Reality Annual International Symposium. (38-44). Albuquerque, NM. IEEE..

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B. Watson, V. Spaulding, N. Walker, and W. Ribarsky. Evaluation of the Effects of Frame Time Variation on VR Task Performance. In Proceedings of the Virtual Reality Annual International Symposium, page 38, 1997.

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B. Watson, V. Spaulding, N. Walker, and W. Ribarsky. Evaluation of the Effects of Frame Time Variation on VR Task Performance. In Proceedings of the Virtual Reality Annual International Symposium, page 38, 1997.

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