Although virtual reality hardware is now widely available, the uptake of real walking is hindered by the fact that it requires often impractically large amounts of physical space. To address this, we present VirtualSpace, a novel system that allows overloading multiple users immersed in different VR experiences into the same physical space. VirtualSpace accomplishes this by containing each user in a subset of the physical space at all times, which we call tiles; app-invoked maneuvers then shuffle tiles and users across the entire physical space. This allows apps to move their users to where their narrative requires them to be while hiding from users that they are confined to a tile. We show how this enables VirtualSpace to pack four users into 16m².

We present a system that complements virtual reality experiences with passive props, yet still allows modifying the virtual world at runtime. The main contribution of our system is that it does not require any actuators; instead, our system employs the user to reconfigure and actuate otherwise passive props. We demonstrate a foldable prop that users reconfigure to represent a suitcase, a fuse cabinet, a railing, and a seat. A second prop, suspended from a long pendulum, not only stands in for inanimate objects, but also for objects that move and demonstrate proactive behavior, such as a group of flying droids that physically attack the user. Our approach conveys a sense of a living, animate world, when in reality the user is the only animate entity present in the system, complemented with only one or two physical props.

We introduce mutual human actuation, a version of human actuation that works without dedicated human actuators. The key idea is to run pairs of users at the same time and have them provide human actuation to each other. Our system, Mutual Turk, achieves this by (1) offering shared props through which users can exchange forces while ob- scuring the fact that there is a human on the other side, and (2) synchronizing the two users’ timelines such that their way of manipulating the shared props is consistent across both virtual worlds.

In this project, we explored how to add haptics to walls and other heavy objects in virtual reality. Our main idea is to prevent the user’s hands from penetrating virtual objects by means of electrical muscle stimulation (EMS). Figure 1a shows an example. As the shown user lifts a virtual cube, our system lets the user feel the weight and resistance of the cube. The heavier the cube and the harder the user presses the cube, the stronger a counterforce the system generates. Figure 1b illustrates how our system implements the physicality of the cube, i.e., by actuating the user’s opposing muscles with EMS.

For my master thesis at the Universitat Pompeu Fabra in Barcelona, Spain, I focused on Virtual Reality applications for motor relearning, which benefit stroke therapy. In a study participants were to perform reaching tasks within a gamified context while being provided with feedback towards self-comparative mastery and other-comparative ego goals. This work is published at the Journal of Disability and Rehabilitation. My master was funded by the German Academic Scholarship Foundation.

For my bachelor thesis at the University of Konstanz, Germany, I developed "Invasion of the Wrong Planet" - a game played on a hybrid interactive surface for cognitive-behavioral therapy for children with conditions in the autistic spectrum. This project has been awarded with the Karl-Steinbuch Stipendium by the MFG Stiftung Baden-Württemberg and the VEUK award of the University of Konstanz. I presented this work at CHI '13 and '14 as a Workshop and WIP.

We present Stuff-Haptics, a software tool that provides consistent storylines across limited, uncurated sets of physical props. Unlike traditional passive haptics experiences, Stuff-Haptics does not require the set of physical props to be premeditated, and allows experiences to run anywhere, specifically in users’ homes. Stuff-Haptics accomplishes this with a prop-independent representation of the storyline, i.e., the narrative structure of events and the layouting rules for mapping of virtual content onto the available physical prop set. Stuff-Haptics lays out the virtual objects onto an annotated scan of the stuff in users homes. Given limited sets of props, Stuff-Haptics offers different solutions to best preserve the experience, either through re-use of props or by pruning the storyline to still fit the most important story elements. In our user studies, Stuff-Haptics both successfully ran the same experience for different users’ prop sets and ran different passive haptics experiences on the same prop set.

We propose a new genre of mixed reality games, that make users perform physically demanding tasks as a byproduct of game play. We illustrate this at the example of Tower Pretense, a tower defense style game that as a side effect makes users move their household. We explain the design of such games that (1) have a consistent virtual game world, (2) match the physical world (such as users vacuuming their floor while virtually they are curling on ice), and (3) fulfill a purpose (such as cleaning windows and whiteboards while virtually chopping up fruits). Our main contribution is that we put mixed reality gamers to productive use. Participants of our user study enjoyed moving heavy boxes more when immersed in Tower Pretense (5.9 vs. 2.1/7) and they were less aware of the physical labor they performed (4.4 vs. 6.9/7).