Tools and Techniques for Mixed Reality Authoring Florian Ledermann and Dieter Schmalstieg Vienna University of Technology {ledermann | schmalstieg}@ims.tuwien.ac.at Abstract While Mixed Reality (MR) technology is steadily matur- ing, application development is still lacking advanced au- thoring tools – even the simple presentation of information, which should not require any programming, is not system- atically addressed by development tools. Moreover, there is also a severe lack of agreed techniques or best practices for the structuring of MR content. In this paper we present APRIL, the Augmented Presentation and Interaction Lan- guge, an authoring platform for MR presentations which provides tools and techniques that are independent of spe- cific applications or target hardware platforms, and should be suitable to raise the level of abstraction on which MR content creators can operate. 1. Introduction For Augmented Reality (AR) and Mixed Reality (MR) technologies to become exposed to a larger audience, we do not only need to build systems that can be used intuitively by untrained people, but also have to provide content that makes use of the special features this new media provides. Without elaborating on possible or sensible usage scenarios of MR systems, it can be said that the huge potential of these systems lies in the presentation of information: be it an out- door tourist guide, a novel navigation system, a museum installation or an educational setting (to mention a few of the more common MR scenarios). The focus of these appli- cations is on the presentation of information in a temporally and spatially structured manner, and on allowing the user to interact with this presentation in order to browse, filter and search according to her needs and interests. Obviously, the user interfaces to support these tasks should be as simple and intuitive as possible. However, we want to make use of the full range of de- vices, tools and paradigms that MR research has produced and is continuing to produce, to support these presenta- tions. Presentations should be able to address the full range of Mixed Reality technologies, including classical AR dis- Figure 1. Two users with different AR plat- forms using the same application, a “Magic Book” created with the APRIL authoring toolkit. plays, but also electronically enhanced physical objects, im- mersive projection technology or portable devices. Con- sequently, we are dealing with complex hardware setups, using nonstandard displays, multi-modal input devices and customized interaction tools in networked multi-host se- tups, incorporating personal computers running different operating systems, but also handheld devices and even cell- phones. And while part of this heterogeneity can be ac- counted to the transient nature of research prototypes, the increased efforts to provide ubiquitous Mixed Reality ser- vices and applications indicates that these hybrid systems will soon be more common that any controlled, single-user single-host setups. Providing facilities for non-programmers to create pre- sentations for such systems is a challenging task. The com- plexity of the underlying system should be hidden from the author, while at the same time allowing her to make use of the unique properties of such a system. Therefore, the first goal in the process of designing an authoring framework was to identify the key concepts that are needed by authors to create compelling MR presentations. These concepts had then to be implemented on top of our existing systems to