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Virtual graffiti consists of virtual objects and/or digital messages, images, multimedia or other annotations or graphics applied to public locations, landmarks or surfaces such as walls, train stations, bridges, etc. Virtual graffiti applications utilize augmented reality and ubiquitous computing to anchor virtual graffiti to physical landmarks or objects in the real world. The virtual content is then viewable through devices such as personal computers, smartglasses, set-top boxes or mobile handsets, such as mobile phones or PDAs. The virtual world provides content, graphics, and applications to the user that are not available in the real world. Virtual graffiti is a novel initiative aimed at delivering messaging and social multimedia content to mobile applications and devices based on the location, identity, and community of the participating entity.
This overall effort focuses on creating new mobile experiences based on merging virtual reality, telepresence, and location-based services. These experiences are seen to evolve over time based on the needs and capabilities of the users.
This set of use cases is centered on a mobile user receiving or sending a message based on the computed location of the user. These include experiences such as
These use cases are important because they serve as a basis from which the other use cases are built. The resolution of the messaging content is directly related to the accuracy with which the location can be computed.
This involves anchoring a virtual reality experience at a physical location. Thus the experiences in the virtual world can only be had at a specific real location. Several use cases that are included here are
The phrase "virtual graffiti" has existed for a long time and has been applied to numerous different applications over the years. Originally, it referred to posting messages on electronic bulletin board systems and marking up whiteboard applications. From there, it developed in academia into contextual messaging applications. Several such examples are given below.
Contextual messaging refers to leaving some type context-specific annotation, e.g. a virtual post-it note on a computer monitor, a time-sensitive message attached to a conference room telling the occupants you won’t be attending a meeting or location-based graffiti on a physical object.
Researchers at the University of Salford experimented with a CAVE system in which a user could mark up a scene using 6-degree of freedom sensors. Obviously this is not something that is suitable for immediate use or mass market applications, but it serves as starting point from which other work could be derived.
Kit Hughes, during a research fellowship at the University of Georgia in 2003, developed a system in which users with WiFi-enabled mobile devices could mark up buildings in downtown Athens, Georgia with their own virtual graffiti via a process known as tagging. In this system, the buildings are selected on a map and the graffiti is stored in a database where it can be accessed from other mobile devices and the project’s website.
A location-based messaging system for leaving virtual post-it notes on physical objects was developed at the National University of Singapore. The system uses mobile devices as AR interfaces to view virtual messages associated with fiducial markers on physical objects.
In a project from Lancaster University, mobile phones are used as digital spray cans. RFID tags are used to identify objects that can be marked up. The RFID tags can hold the identities of the last five people to leave graffiti. The graffiti itself is stored on a server indexed by RFID tag. When another user comes within range of an RFID-tagged object, the graffiti associated with that object is downloaded into their mobile device.
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