From Single-user to Multi-user 3D Content Creation (Issues in Creation, Management, Search and Presentation of Interactive 3D Content)

In many application areas, such as entertainment, social networking or education, there are clear advantages of employing multi-user collaborative virtual environments. Such environments enable users to navigate in a shared virtual space and interact with virtual objects and avatars representing other users [1, 15, 59, 61, 64, 74].

Beyond the advantages of communicating with other users, collaborative virtual environments may help to further reduce the content creation problem. Even with the use of simplified content creation methods, the process of creating complex behavior-rich 3D content is laborious and time consuming. Multi-user environments that allow their users to create content in a social way provide a clear advantage [47]. User-generated content is not only cheaper to develop and maintain but also more authentic and closer to users who invest their time and emotions in the creation process.

However, the development of virtual environments supporting user-generated content meets a natural barrier if users cannot be sure whether they are able to control access to their content. To encourage users to actively participate in content development, it is necessary to assure that: (1) the user content will not be misused in any part; (2) interacting with content populating the environment is safe; (3) author rights to the content will be preserved.

Another level of collaboration between users can be achieved by building federated virtual environments. Federalization of virtual environments enables users of different virtual environments to collaborate and gives access to a broader range of services and up-to-date digital assets coming from different sources [38]. Federated virtual environments are more attractive to users and are able to keep larger communities alive. Technically, federalization enhances scalability, extensibility, capability of specialization of a virtual environment system and the level of data and code reuse [3, 16, 29]. This, however, reinforces the security considerations because of limited control over the heterogeneous, distributed computing infrastructure used for running such federated virtual environments.

Coarse-grained access control and authentication assuring data protection for virtual environments are implemented based on research results in the domains of CAD 3D virtual environments and massively-used virtual worlds. Access control model of the commercial or open source virtual worlds is usually very simple: only few operations from predefined list can be used to form user privileges. In the domain of protecting the rights to data in virtual environments, outputs of research on cryptography and 3D digital watermarking are applied, but they concern only geometry of protected static 3D models, or their compositions that constitute the content of 3D virtual environments.

In modern, interactive, behavior-rich multi-user virtual environments, which are based on user-generated content and run on heterogeneous distributed computing infrastructure, security considerations become of critical importance. Coarse-grained access control and authorization methods cease to be sufficient. Insufficient are also methods of privilege modeling developed so far, which are either geometry-centric with no advanced interaction support or coarse-grained with no flexible privilege modeling capabilities. New methods are required, yet they cannot impose too many restrictions in the phase of creation of users’ objects because modern virtual environments intentionally promote user creativity and sociability. Protection should concern not only geometrical data (3D models), their relationships and structure, classical numeric, text and multimedia data (accessible by a 3D interface of the virtual environment) but also behavioral interactions between objects.

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