Ubiquitous Interaction

We explored different technologies and mechanisms to enable interaction in ubiquitous environments.

Exploiting Thermal Reflection for Interactive Systems

aluThermal cameras have recently drawn the attention of HCI researchers as a new sensory system enabling novel interactive systems. They are robust to illumination changes and make it easy to separate human bodies from the image background. Far-infrared radiation, however, has another characteristic that distinguishes thermal cameras from their RGB or depth counterparts, namely thermal reflection. Common surfaces reflect thermal radiation differently than visual light and can be perfect thermal mirrors. In this paper, we show that through thermal reflection, thermal cameras can sense the space beyond their direct field-of-view. A thermal camera can sense areas besides and even behind its field-of-view through thermal reflection. We investigate how thermal reflection can increase the interaction space of projected surfaces using camera-projection systems. We moreover discuss the reflection characteristics of common surfaces in our vicinity in both the visual and thermal radiation bands. Using a proof-of-concept prototype, we demonstrate the increased interaction space for hand-held camera-projection system. Furthermore, we depict a number of promising application examples that can benefit from the thermal reflection characteristics of surfaces.


Modeling Distant Pointing for Compensating Systematic Displacements

Distant pointing at objects and persons is a highly expressive gesture that is widely used in human communication. Point- ing is also used to control a range of interactive systems. For determining where a user is pointing at, different ray casting methods have been proposed. In this paper we assess how accurately humans point over distance and how to improve it. Participants pointed at projected targets on a wall display from 2m and 3m while standing and sitting. Testing three common ray casting methods, we found that even with the most accurate one the average error is 61.3cm. We found that all tested ray casting methods are affected by systematic dis- placements. Therefore, we trained a polynomial to compen- sate this displacement. We show that using a user-, pose-, and distant-independent quartic polynomial can reduce the aver- age error by 37.3%.


Alireza Sahami Shirazi, Yomna Abdelrahman, Niels Henze, Stefan Schneegass, Mohammadreza Khalilbeigi, and Albrecht Schmidt. 2014. Exploiting thermal reflection for interactive systems. Proceedings of the 32nd annual ACM conference on Human factors in computing systems - CHI ’14: 3483–3492. http://doi.org/10.1145/2556288.2557208

Sven Mayer, Katrin Wolf, Stefan Schneegass, and Niels Henze. 2015. Modeling Distant Pointing for Compensating Systematic Displacements. Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, ACM.