Wloka, M., "Lag in Multiprocessor Virtual Reality," Presence: Teleoperators and Virtual Environments, Vol. 4, No. 1, MIT Press, Cambridge MA, Winter 1995, pp. 50-63.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....system behavior and complain that the system is unresponsive. Indeed, Liu et al. 1] found lag time to be as important as the frame rate for effective use of immersive displays. Researchers have studied lag in the context of teleoperated machines, head mounted displays, and telepresence systems [1, 2]. Liu et al. 1] conducted experiments on a telemanipulation system and found the allowable lag time to be 100 ms (0.1 s) and 1000 ms (1 s) for inexperienced and experienced users, respectively. In [3] the work on lag models was extended to include scientific simulations with interactive, ....

M. Wloka, "Lag in Multiprocessor Virtual Reality, " Presence, Vol. 4, 1995, pp. 50--63.

....time limit for user input should not be a problem. Assuming that the application uses prediction to overcome input device latency, new input is ready in the time it takes a new device sample to arrive and be processed by the prediction technique. The times involved in both steps are modest. Wloka [Wlo94] describes measurements of these times for one particular hardware configuration; similar empirical tests could determine the times for other situations. Limiting the time involved in updating behavior is less straightforward. In sophisticated applications, the algorithms that compute behavior ....

....Bar91, BW92] unfortunately do not lend themselves to time limits. This section has not distinguished between single processor and multiple processor applications. Multiple processors can help an application perform its activities more quickly, but they complicate the issue of latency. Wloka [Wlo94] discusses this problem and presents some pragmatic solutions. To summarize this section, it is clear that the problem of bounding per frame computations still offers many opportunities for research. Fortunately, the suggestions from this section, combined with the mechanisms from Chapters 4 ....

Matthias M. Wloka. Lag in Multiprocessor Virtual Reality. Presence, volume 3, number 4, 1994.

....lag time, i.e. the delay between a user action and the display of the result of that action. Liu et al. 9] found lag time to be equally important as frame rate for immersive displays. Lag has been studied in the context of teleoperated machines, head mounted displays, and telepresence systems [9, 16]. The goal of this paper is to extend these models and techniques for lag analysis to include integrated supercomputer applications with interactive, immersive virtual interfaces. The addition of supercomputer simulations into the virtual environment increases the complexity of the models. Hence, ....

....Laboratory (the site where this study was conducted) in Section 3. We present our general model for end to end lag in Section 4. The findings of the case study are given in Section 5. We discuss methods for reducing the lag in Section 6 and summarize the paper in Section 7. 2 Previous Work In [16] Wloka presents a thorough analysis of lag time in multiprocessor virtual reality systems. The focus is on the viewpoint lag. He identifies the various sources of lag time: input device lag time required to obtain position and angle measurements of input device, application lag ....

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Wloka M. Lag in Multiprocessor Virtual Reality. Presence 1995; 4:50-63

....an interaction and the result of that interaction (or lag) is too great, users find it difficult to maintain fine control over system behavior and complain that the system is unresponsive. Lag has been studied in the context of teleoperated machines, head mounted displays, and telepresence systems [12, 20]. In experiments on a telemanipulation system, Liu and his colleagues [12] found the allowable lag time to be 100 ms (0.1 s) and 1000 ms (1 s) for inexperienced and experienced users, respectively. In [18] the work on lag models was extended to include scientific simulations with interactive ....

....of memory for reference by Render0. All five processes operate asynchronously. 3 End to End Lag The lag time of a virtual environment is highly dependent on the application. There are, however, standard components of the end to end lag for a virtual environment coupled with scientific simulations [19, 20]. These components consists of the following: tracking, rendering, simulation, synchronization, frame rate, and network. They are described in detail below. The tracking lag is the time required to obtain the position and orientation of the user with the tracked devices. This lag time is dependent ....

M. Wloka, "Lag in Multiprocessor Virtual Reality, " Presence, (4), 1995, pp. 50--63.

....vision with computergenerated imagery. To make such systems and their applications effective, the synthetic or virtual imagery needs to blend convincingly with the real images. Towards this goal, researchers study such areas as minimizing object registration errors [2] and overall system lag [2] [17] so as to increase the realness of virtual objects. Since occlusion provides a significant visual cue to the human perceptual system when displaying data in three dimensions, proper occlusion resolution between real and virtual objects is highly desirable in augmented reality systems. However, ....

Wloka, Matthias M. Lag in Multiprocessor Virtual Reality. Presence, 4(1), 1994. To appear.

....that the system is unresponsive. Indeed, Liu et al. Liu et al. 1993] found lag time to be as important as the frame rate for effective use of immersive displays. Lag has been studied in the context of teleoperated machines, head mounted displays, and telepresence systems [Liu et al. 1993, Wloka, 1995] Liu et al. Liu et al. 1993] conducted experiments on a telemanipulation system and found the allowable lag time to be 100 ms (0.1s) and 1000 ms (1s) for inexperienced and experienced users, respectively. In [Taylor et al. 1995] the work on lag models was extended to include scientific ....

....by an outline of the supercomputer visualization environment in x3. The general model for end to end lag is given in x4, followed by the case study s findings in x5. This is followed by a discussion of methods for reducing the lag in x6. Finally, we summarize our results in x7. 2 Previous Work In [Wloka, 1995], Wloka presents a thorough analysis of lag time in a multiprocessor virtual reality system; the multiprocessors execute the calculations necessary to render an image. The focus is on viewpoint lag. He identifies the various sources of lag time: input device lag the time required to obtain ....

Wloka, M. 1995. Lag in Multiprocessor Virtual Reality. Presence. 4:50-63.

....our new technique maintains discrete frames, i.e. strictly speaking it is not frameless. 1.1 Benefits and Drawbacks Practically frameless rendering hasmany advantages. Most notably, it sharply increasesframe rate (see Section 4) The increasedframerate in turn reduces end to end lag [14], thus making applications more usable [7] 10] More important, increasing frame rate in head mounted displays beyond a certain threshold (typically around 10 frames per second) boosts user performance dramatically for certain tasks [10] Box 1910, Department of Computer Science, Brown ....

Matthias M. Wloka. Lag in multiprocessor virtual reality. Presence, 4(1), 1994.

....multiple processors in a pipelined configuration increases throughput yet maintains the same lag. A VR system has several characteristic lag sources. The following two sections describe these sources and how to combat the lag, respectively. Additional information about lag in VR is described in (Wloka, 1995). 7.1 Lag sources in VR systems User input device lag The user input device in a VR application reports 3D position and orientation data. It is external to the host workstation and typically communicates data via the serial port. Total user input User Display Renderer Application Tracker ....

Wloka, M.M. (1995) Lag in multiprocessor virtual reality. PRESENCE: Teleoperators and Virtual Environments, 4(1).

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Wloka, M., "Lag in Multiprocessor Virtual Reality," Presence: Teleoperators and Virtual Environments, Vol. 4, No. 1, MIT Press, Cambridge MA, Winter 1995, pp. 50-63.

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Wloka95 Wloka, Mathhhias M. 1995. "Lag in Multiprocessor Virtual Reality, " PRESENCE: Teleoperators and Virtual Environments 4.1, Winter 1995, pp. 50-63.

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Wloka M (1995) Lag in Multiprocessor Virtual Reality. PRESENCE: Teleoperators and Virtual Environments 4(1): 50-63.

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Wloka M (1995) Lag in Multiprocessor Virtual Reality. PRESENCE: Teleoperators and Virtual Environments 4(1): 50-63.

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