Malte Weiß
HCI Research · Software Development

SLAP Widgets (2008-2009)

SLAP Widgets are translucent physical controls for interactive tabletops. They provide rich haptic feedback and can change their visual appearance on the fly. This photo shows the turnable and pushable SLAP Knob.

Interactive tabletops only provide limited haptic feedback. Most touch screens usually display on-screen user interface elements that can be triggered by touch. However, users cannot feel on-screen controls: They cannot sense the range of an on-screen slider or the pressure-point of a button. Thereby, interacting with most interactive surface requires visual focus; users have to look at the controls they operate, which limits efficiency. Furthermore, interacting with on-screen controls is less accurate than with conventional physical controls. SLAP Widgets addresses this problem.

SLAP Widgets are physical general-purpose controls, including buttons, sliders, knobs, and keyboards. They are made of transparent materials, silicone and acrylic. They combine the benefits of conventional controls and on-screen UI elements: First, they provide haptic feedback, guide the users motion, and, thereby, enable eyes-free interaction. Second, they are transparent which allows to use the table’s back-projection to change their visual appearance on the fly. For example, if text entry is required, a SLAP Keyboard can be “slapped” on the surface. A keyboard layout appears and users can start typing with haptic feedback. Thanks to its translucency, the software can switch the layout during runtime, e.g., between German and English layout.

SLAP Widgets are passive device that do not need any electronic parts. They are mounted on paper-based markers that are tracked by a camera in the table. Thereby, our controls are robust, lightweight, and easy to prototype.


Software architecture
Video Presentation of SLAP Widgets on YouTube:


Context This project is part of my PhD.
  • Hardware infrastructure: Interactive tabletop based on optical tracking, and projector-based rendering.
  • Tangibles: Custom-made by laser-cutting acrylic and casting silicone
  • Programming languages: Objective-C
  • Used frameworks: OpenGL, MultiTouchFramework, SLAP Framework
Team This project was developed in collaboration with the University of California, San Diego, by
  • Malte Weiss
  • Julie Wagner
  • Yvonne Jansen
  • Jan Borchers
  • Roger Jennings
  • Ramsin Khoshabeh
  • Jim Hollan

Further Information

Details You find a detailed description of SLAP Widgets in my PhD thesis in chapter 3 (pdf, 7.5 MB).
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