The Role and Relevance of Experimentation in Informatics

Informatics is a relatively young eld within sci- ence and engineering. Its research and develop- ment methodologies build on the scientic and de- sign methodologies in the classical areas, often with new elements to it. We take an in-depth look at one of the less well-understood methodologies in infor- matics, namely experimentation. What does it mean to do experiments in in- formatics? Does it make sense to `import' tradi- tional principles of experimentation from classical disciplines into the eld of computing and informa- tion processing? How should experiments be docu- mented? These are some of the questions that are treated. The report argues for the key role of empiri- cal research and experimentation in contemporary Informatics. Many IT systems, large and small, can only be designed sensibly with the help of experiments. We recommend that professionals and students alike are well-educated in the prin- ciples of sound experimentation in Informatics. We also recommend that experimentation protocols are used and standardized as part of the experimental method in Informatic

Scene-motion- and latency-perception thresholds for head-mounted displays

A fundamental task of an immersive virtual environment (IVE) system is to present images of the virtual world that change appropriately as the user's head moves. Current IVE systems, especially those using head-mounted displays (HMDs), often produce spatially unstable scenes, resulting in simulator sickness, degraded task performance, degraded visual acuity, and breaks in presence. In HMDs, instability resulting from latency is greater than all other causes of instability combined. The primary way users perceive latency in an HMD is by improper motion of scenes that should be stationary in the world. Whereas latency-induced scene motion is well defined mathematically, less is understood about how much scene motion and/or latency can occur without subjects noticing, and how this varies under different conditions. I built a simulated HMD system with zero effective latency---no scene motion occurs due to latency. I intentionally and artificially inserted scene motion into the virtual environment in order to determine how much scene motion and/or latency can occur without subjects noticing. I measured perceptual thresholds of scene-motion and latency under different conditions across five experiments. Based on the study of latency, head motion, scene motion, and perceptual thresholds, I developed a mathematical model of latency thresholds as an inverse function of peak head-yaw acceleration. Psychophysics studies showed that measured latency thresholds correlate with this inverse function better than with a linear function. The work reported here readily enables scientists and engineers to, under their particular conditions, measure latency thresholds as a function of head motion by using an off-the-shelf projector system. Latency requirements can thus be determined before designing HMD systems