ARCS/en
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ARCS (for Augmented Reality Component System) is a framework dedicated to the design of augmented reality applications. The core of the framework is a general purpose component system cutomized to meet the requirements of augmented reality applications (mostly real-time constraints). A set of components is developped on top of this system for augmented reality applications.
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Basics
Components
According to Szyperski’s definition [Szyperski02], “A component is a coherent package of software that can be independently developed and delivered as a unit, and that offers interfaces by which it can be connected, unchanged, with other components to compose a larger system”.
It means that, the way components will communicate with each other should be described, how they’re implemented, how they’re initialized and how we can use them to build applications.
Before detailing our components, we should introduce the main communication mechanism we use, which is based on the signal/slot paradigm.
Signal/slots
Our solution is based on the signal/slot communication model between components. This paradigm, mainly used in user interfaces API, tends to reach other scopes of specific programming. Some libraries are implementing it, for example: QT [1], libsigc++ [2] derived from GTK+, sigslot [3] and boost [4]. Signals represent callbacks with multiple targets. Signals are connected to some set of slots, which are callback receivers. They are triggered when the signal is ”emitted”. Signals and slots can be connected and disconnected dynamically at runtime and are managed. That is to say, connections are tracked by objects owning signals and slots. They’re able to automatically disconnect signal/slot connections when one of the object involved in communication is destroyed. This allows the user to make signal/slot connections without expending a great effort to manage the lifetimes of those connections with regard to the lifetimes of all objects involved.
Why programming with components ?
During the last years, AR (Augmented Reality) community has proven the need of an infrastructure. Almost 30 different projects of framework have been developed for AR [Endres05].
Amongst these projects, the most remarkable ones are :
- Studierstube, one of the oldest project relying on a ditributed scenegraph,
- Tinmith, which is oriented for developpers,
- Dwarf, developped for distributed augmented reality services,
- AMIRE, which is the closest architecture to ARCS.
Our choice is to develop or rely on a component system that meets several requirements such as portability, a variable granularity, some scalability, and a high level of abstraction for end-users. As we will see, we will introduce component life-cycle management mechanisms in ours application developed with our framework. We will also combined it with with a system allowing on-line reconfiguration of data-flow.
The ARCS Core
Components
Compositions of components
The sheet, an explicit composition
Initialisations of components
Other composition mechanism
Extending the sheet capabilities
Publications
J.Y. Didier, S. Otmane, M. Mallem - A Component Model for Augmented/Mixed Reality Applications with Reconfigurable Data-flow
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