. This paper reports on an in-house designed TUI performing 3D optical tracking of an interaction cube. Such systems can benefit 3D interaction by offering a more direct form of interaction coming closer to the use of physical artefacts and tools. This offers users a more natural use of hand and body movements. Such movements may hence be integrated into the interaction with digital information, thereby supporting a fluent handling of 3D models [5] . Based on a Tangible User Interface (TUI), the application Augmented Chemistry (AC) was designed. The AC system is a workbench offering its users to see and to interact with 3D molecular models in an 'intuitive' and 'direct' way. The system also offers tools to build composite molecular models. Following a common use of AR Toolkit [2], a cube with printed patterns is connected to an animated 3D model and both are seen in a mirror image. Using a specialized select-and rotate-tools, single atoms can be picked up, positioned, and composed into complete molecules. Chemical rules can be formulated and integrated into the application, thus enabling the construction of basic structures as appearing in the nature, for instance water. Augmented Chemistry (AC) is a workbench consisting of a table and a rear-projection screen (Fig. 1) . The screen is based on acrylic glass from Lumin™. It is particularly well suited for rear-projection and also works well under daylight conditions. Right below the screen sits a camera recording user interaction taking place upon and above the tabletop. The screen displays what this camera sees. Such a display is meant to give the user the feeling of a mirror. This mirror image is then enriched with a virtual environment. Users interact with models in this virtual environment using a booklet, a cube, a platform, and a so-called Gripper. Each page in the booklet is used to identify an element of the periodic table. The booklet, the platform, and the Gripper each carry a pattern; the cube carries six patterns − one per page. A 3D model augments the mirror image of a booklet page, a platform, a cube, or a Gripper (Fig. 2) . Hence, users can select, position, rotate, compose, and deselect 3D models, thereby affecting the virtual environment.
However, they did not specify in details why such a display was used other that it was meant to give the feeling of a mirror image of the interaction space REF .
Augmented Chemistry: an interactive educational workbench
Proceedings. International Symposium on Mixed and Augmented Reality
Proceedings. International Symposium on Mixed and Augmented Reality
Computer Science