In recent years interactive visualization of 3D data has become important and widespread due to the requirements of several application areas. However, current user interfaces often lack adequate support for 3D interactions: 2D desktop systems are often limited in cases where natural interaction with 3D content is required, and 3D user interfaces consisting of stereoscopic projections and tracked input devices are rarely adopted by ordinary users.

Touch interaction has received considerable attention for 2D interfaces, and more recently for 3D interfaces. Many touch devices now support multiple degrees of freedom input by capturing multiple 2D contact positions on the surface as well as varying levels of pressure and even depth. There is great potential for multi-touch interfaces to provide the traditionally difficult to achieve combination of natural 3D interaction without any instrumentation. When combined with a stereoscopic display as well as depth cameras, multi-touch technology have the potential to form the basis for a next generation of 3D user interfaces.

Our Dagstuhl seminar Touching the 3rd Dimension focussed on bringing together researchers from a diverse set of fields of Computer Science to discuss the next generation of user interfaces based on multi-touch technology as well as 3D visualization. It is envisaged that such user interfaces will be fundamentally different to the current multi-touch systems that are being deployed in mobile devices, desktop environments as well as entertainment systems. First, future stereoscopic displays will work without the need for users to wear cumbersome 3D stereo glasses. In this context autostereoscopic displays have already been deployed for personal working spaces as well as entertainment systems, but are still rarely used due to technical limitations such as low resolution and lacking multi-viewpoint support. Second, future multi-touch technology will not be limited by planar screens, but touch surfaces may be of arbitrary shapes. Furthermore, touch interactions in space will be possible, while still providing the user haptic feedback, for example, by the usage of air pressure devices.