Thorsten Karrer

MudPad: tactile feedback and haptic texture overlay for touch surfaces

We introduce MudPad, a system capable of localized active haptic feedback on multitouch screens. We use an array of electromagnets combined with an overlay containing magnetorheological (MR) fluid to actuate a tablet-sized area. As MudPad has a very low reaction time it is able to produce instant multi-point feedback for multitouch input, ranging from static levels of surface softness to a broad set of dynamically changeable textures. Our system does not only convey global confirmative feedback on user input but allows the UI designer to enrich the entire interface with a tactile layer conveying local semantic information. This also allows users to explore the interface haptically.

DRAGON: a direct manipulation interface for frame-accurate in-scene video navigation

We present DRAGON, a direct manipulation interaction technique for frame-accurate navigation in video scenes. This technique benefits tasks such as professional and amateur video editing, review of sports footage, and forensic analysis of video scenes. By directly dragging objects in the scene along their movement trajectory, DRAGON enables users to quickly and precisely navigate to a specific point in the video timeline where an object of interest is in a desired location. Examples include the specific frame where a sprinter crosses the finish line, or where a car passes a traffic light. Through a user study, we show that DRAGON significantly reduces task completion time for in-scene navigation tasks by an average of 19-42% compared to a standard timeline slider. Qualitative feedback from users is also positive, with multiple users indicating that the DRAGON interaction felt more natural than the traditional timeline slider for in-scene navigation.

Twend: twisting and bending as new interaction gesture in mobile devices

In this work we present a hardware prototype that uses bending gestures as input for a mobile device and experimental setups that compare possible gestures with other, more traditional input methods in mobile computing. These will eventually result in guidelines for researchers and designers how to build bendable devices and show new interaction metaphors for computer user interfaces.

Fly: a tool to author planar presentations

Modern presentation software is still built around interaction metaphors adapted from traditional slide projectors. We provide an analysis of the problems in this application genre that presentation authors face and present Fly, a presentation tool that is based on the idea of planar information structures. Inspired by the natural human thought processes of data chunking, association, and spatial memory, Fly explores authoring of presentation documents. Evaluation of a paper prototype showed that the planar UI is easily grasped by users, and leads to presentations more closely resembling the information structure of the original content, thus providing better authoring support than the slide metaphor. Our software prototype confirmed these results, and outperformed PowerPoint in a second study for tasks such as prototyping presentations and generating meaningful overviews. Users reported that this interface helped them better to express their concepts, and expressed significant preference for Fly over the traditional slide model.

Toward a Framework for Interactive Systems to Conduct Digital Audio and Video Streams

21 Following advances in hardware and computing power, interactive conducting systems have grown in complexity and capability. Modern conducting systems incorporate research from a variety of disciplines, including motion tracking, gesture recognition and interpretation, and digital signal processing. Frameworks have emerged in recent years to enable rapid development of such complex systems, including Max/MSP for manipulating and processing synthesized and sampled audio (Puckette 2002) and EyesWeb for gesture tracking (Camurri, Mazzarino, and Volpe 2003). Today’s computers are, moreover, able to handle large chains of complex filters and other operations on digitally sampled audio and video streams in real time. In contrast, modern computer-music systems often do not take full advantage of these capabilities by continuing to use synthesized music, usually MIDI-based; even fewer incorporate video. Using synthesized music over digitally sampled audio streams affords a higher level of semantic access to the data, such as beats, notes, and voicings. However, digital audio and video recordings can offer a higher level of fidelity and realism: today’s synthesizing technology is still unable to reproduce, for example, the unique character of the Vienna Philharmonic playing in their Golden Hall of Vienna’s Musikverein. Part of the problem can be attributed to the difficulty of working with time-based effects in current multimedia frameworks such as Apple’s QuickTime, Microsoft’s DirectShow/DirectSound, or Max/MSP. We have encountered some of these difficulties in our own work, which includes a series of interactive conducting systems that incorporate audio and video recordings. These systems have been well-received as museum exhibits around the world. Personal Orchestra, which was coordinated by Max Muhlhauser

Stacksplorer: call graph navigation helps increasing code maintenance efficiency

We present Stacksplorer, a new tool to support source code navigation and comprehension. Stacksplorer computes the call graph of a given piece of code, visualizes relevant parts of it, and allows developers to interactively traverse it. This augments the traditional code editor by offering an additional layer of navigation. Stacksplorer is particularly useful to understand and edit unknown source code because branches of the call graph can be explored and backtracked easily. Visualizing the callers of a method reduces the risk of introducing unintended side effects. In a quantitative study, programmers using Stacksplorer performed three of four software maintenance tasks significantly faster and with higher success rates, and Stacksplorer received a System Usability Scale rating of 85.4 from participants.

iSymphony : an adaptive interactive orchestral conducting system for digital audio and video streams

We present iSymphony, an interactive orchestral conducting system for digital audio and video that adaptively adjusts to the users conducting style. Using a digital baton, users may control the tempo, volume, and instrument emphasis of a digital audio and video recording of an orchestra. The system adaptively recognizes three gesture profiles: the four-beat neutral-legato pattern, an up-down pattern, and random gestures. The system uses an audio time-stretching algorithm we developed that allows the playback speed of a digital audio recording to be arbitrarily adjusted without changing its pitch. iSymphony is an example of how computers can enable more people to experience an interaction style normally limited to a few people (conductors), and is installed as part of the Its Artastic! exhibit at the Betty Brinn Childrens Museum in Milwaukee, USA.

MudPad: localized tactile feedback on touch surfaces

We present MudPad, a system that is capable of localized active haptic feedback on multitouch surfaces. An array of electromagnets locally actuates a tablet-sized overlay containing magnetorheological (MR) fluid. The reaction time of the fluid is fast enough for realtime feedback ranging from static levels of surface softness to a broad set of dynamically changeable textures. As each area can be addressed individually, the entire visual interface can be enriched with a multi-touch haptic layer that conveys semantic information as the appropriate counterpart to multi-touch input.

Fly: an organic presentation tool

In this paper, we present Fly, a prototype presentation system that adds a visual structure to presentations. Current presentation software, like PowerPoint, structure slides in a linear sequence. The Fly design introduces a spatial organization that is based on Mind Maps. Using colour associations, spatial relations, and fluid movement, we show how presentation software can structure a meaningful overview of the underlying content.

DragLocks: handling temporal ambiguities in direct manipulation video navigation

Direct manipulation video navigation (DMVN) systems allow to navigate inside video scenes by spatially manipulating objects in the video. Problems arise when dealing with temporal ambiguities where a time span is projected onto a single point in image space, e.g., when objects stop moving. Existing DMVN systems deal with these cases by either disabling navigation on the paused object or by allowing jumps in the timeline. Both of these workarounds are undesirable as they introduce inconsistency or provoke loss of context. We analyze current practices regarding temporal ambiguities and introduce two new methods to visualize and navigate object pauses. User tests show that the new approaches are better suited for navigation in scenes containing temporal ambiguities and are rated higher in terms of user satisfaction.