Malte Weiss

Rapid acquisition of specular and diffuse normal maps from polarized spherical gradient illumination

We estimate surface normal maps of an object from either its diffuse or specular reflectance using four spherical gradient illumination patterns. In contrast to traditional photometric stereo, the spherical patterns allow normals to be estimated simultaneously from any number of viewpoints. We present two polarized lighting techniques that allow the diffuse and specular normal maps of an object to be measured independently. For scattering materials, we show that the specular normal maps yield the best record of detailed surface shape while the diffuse normals deviate from the true surface normal due to subsurface scattering, and that this effect is dependent on wavelength. We show several applications of this acquisition technique. First, we capture normal maps of a facial performance simultaneously from several viewing positions using time-multiplexed illumination. Second, we show that highresolution normal maps based on the specular component can be used with structured light 3D scanning to quickly acquire high-resolution facial surface geometry using off-the-shelf digital still cameras. Finally, we present a realtime shading model that uses independently estimated normal maps for the specular and diffuse color channels to reproduce some of the perceptually important effects of subsurface scattering.

SLAP widgets: bridging the gap between virtual and physical controls on tabletops

We present Silicone iLluminated Active Peripherals (SLAP), a system of tangible, translucent widgets for use on multitouch tabletops. SLAP Widgets are cast from silicone or made of acrylic, and include sliders, knobs, keyboards, and buttons. They add tactile feedback to multi-touch tables, improving input accuracy. Using rear projection, SLAP Widgets can be relabeled dynamically, providing inexpensive, battery-free, and untethered augmentations. Furthermore, SLAP combines the flexibility of virtual objects with physical affordances. We evaluate how SLAP Widgets influence the user experience on tabletops compared to virtual controls. Empirical studies show that SLAPWidgets are easy to use and outperform virtual controls significantly in terms of accuracy and overall interaction time.

HoloDesk: direct 3d interactions with a situated see-through display

HoloDesk is an interactive system combining an optical see through display and Kinect camera to create the illusion that users are directly interacting with 3D graphics. A virtual image of a 3D scene is rendered through a half silvered mirror and spatially aligned with the real-world for the viewer. Users easily reach into an interaction volume displaying the virtual image. This allows the user to literally get their hands into the virtual display and to directly interact with an spatially aligned 3D virtual world, without the need for any specialized head-worn hardware or input device. We introduce a new technique for interpreting raw Kinect data to approximate and track rigid (e.g., books, cups) and non-rigid (e.g., hands, paper) physical objects and support a variety of physics-inspired interactions between virtual and real. In particular the algorithm models natural human grasping of virtual objects with more fidelity than previously demonstrated. A qualitative study highlights rich emergent 3D interactions, using hands and real-world objects. The implementation of HoloDesk is described in full, and example application scenarios explored. Finally, HoloDesk is quantitatively evaluated in a 3D target acquisition task, comparing the system with indirect and glasses-based variants.

Madgets: actuating widgets on interactive tabletops

We present a system for the actuation of tangible magnetic widgets (Madgets) on interactive tabletops. Our system combines electromagnetic actuation with fiber optic tracking to move and operate physical controls. The presented mechanism supports actuating complex tangibles that consist of multiple parts. A grid of optical fibers transmits marker positions past our actuation hardware to cameras below the table. We introduce a visual tracking algorithm that is able to detect objects and touches from the strongly sub-sampled video input of that grid. Six sample Madgets illustrate the capabilities of our approach, ranging from tangential movement and height actuation to inductive power transfer. Madgets combine the benefits of passive, untethered, and translucent tangibles with the ability to actuate them with multiple degrees of freedom.

FingerFlux: near-surface haptic feedback on tabletops

We introduce FingerFlux, an output technique to generate near-surface haptic feedback on interactive tabletops. Our system combines electromagnetic actuation with permanent magnets attached to the users hand. FingerFlux lets users feel the interface before touching, and can create both attracting and repelling forces. This enables applications such as reducing drifting, adding physical constraints to virtual controls, and guiding the user without visual output. We show that users can feel vibration patterns up to 35 mm above our table, and that FingerFlux can significantly reduce drifting when operating on-screen buttons without looking.

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.

BendDesk: dragging across the curve

We present BendDesk, a hybrid interactive desk system that combines a horizontal and a vertical interactive surface via a curve. The system provides seamless touch input across its entire area. We explain scalable algorithms that provide graphical output and multi-touch input on a curved surface. In three tasks we investigate the performance of dragging gestures across the curve, as well as the virtual aiming at targets. Our main findings are: 1) Dragging across a curve is significantly slower than on flat surfaces. 2) The smaller the entrance angle when dragging across the curve, the longer the average trajectory and the higher the variance of trajectories across users. 3) The curved shape of the system impairs virtual aiming at targets.

Multi-user interaction in virtual audio spaces

Audio guides are a common way to provide museum visitors with an opportunity for personalized, self-paced information retrieval. However, this personalization conflicts with some of the reasons many people go to museums, i.e., to socialize, to be with friends, and to discuss the exhibit as they experience it [1]. We developed an interactive museum experience based on audio augmented reality that lets the visitor interact with a virtual spatial audio soundscape. In this paper, we present some new interaction metaphors we use in the design of this audio space, as well as some techniques to generate a group experience within audio spaces.

A pattern language for interactive tabletops in collaborative workspaces

In this paper, we present a Human-Computer Interaction (HCI) design pattern language that bundles existing knowledge on tabletop design and offers solutions to recurring problems. Our patterns enable not only developers, designers, and domain experts to improve their existing systems and facilitate the design process of new systems, we also encourage novice users to comprehend the variety of tabletop research and commercial products in this domain. We consider our language as a starting point to create a sustainable body of knowledge that will be extended and refined by the community.

Engineering patterns for multi-touch interfaces

Multi-touch gained a lot of interest in the last couple of years and the increased availability of multi-touch enabled hardware boosted its development. However, the current diversity of hardware, toolkits, and tools for creating multi-touch interfaces has its downsides: there is only little reusable material and no generally accepted body of knowledge when it comes to the development of multi-touch interfaces. This workshop seeks a consensus on methods, approaches, toolkits, and tools that aid in the engineering of multi-touch interfaces and transcend the differences in available platforms. The patterns mentioned in the title indicate that we are aiming to create a reusable body of knowledge.