Lag Tests - A Temporal Lag Diagnostic for Virtual and Augmented Environments


Colin Swindells

Improvements in minimally invasive surgery, collaborative computing environments, and computer aided design are a few applications for the goal-directed human hand study and analysis performed in the Enhanced Virtual Hand Lab (EVHL). Instead of using traditional Human Computer Interaction (HCI) media such as a mouse or keyboard, hand gestures and actions are explored in three-dimensional augmented environments. I am currently exploring performance bottlenecks within various configurations of the EVHL software and hardware (see first Figure on the left). Virtual objects within an augmented environment must respond to the user's actions as quickly as possible to provide a compelling experience. Significant resources are required to generate the virtual and augmented objects currently manipulated in the EVHL. A 3-D motion analysis system (OPTOTRAK, Northern Digital, Inc.) tracks physical objects and user actions in the environment; and, a graphics workstation (Onyx2, Silicon Graphics, Inc.) renders graphic objects onto a half-silvered mirror such that the physical and graphic objects appear in the same workspace. Since graphical objects are compared with information from the real world and updated at least 60 times per second, reducing the number of bottlenecks within the EVHL hardware and software is important. My most recent work was to quantify the end-to-end temporal lag of the EVHL system. As shown in the second Figure on the left, a virtual object (white disk) tracked a physical object (black cylinder) on the record player, and lagged by a measurable angle (proportional to the total system lag). Our current worst-case system lag estimate is approximately 50 milliseconds.