Shadow Relationships An Approach for Real-time Shadow Description and Management

H. Drumm (Germany)


shadow, MPEG-4, shadow volumes, graph theory


Authors who create interactive 3D-applications mostly suffer under the absences of an easy shadow creation. Very often shadows are realized as fakes with big efforts for implementation. Even new description languages like MPEG-4 do not support any shadow descriptions for interactive 3D-applications as yet. The lack of existing shadow description possibilities for real-time 3D-applications was the inspiration of our research work. In our option shadows should be as easy to create for interactive real-time 3D-applications as with any ordinary non real-time computer animation tools. A general solution for real-time shadow creation needs to meet many requirements, e.g. a shadow description that is suitable for any 3D-applications, a well thought-out shadow management as well as a suitable real-time shadow algorithm. Complex 3D-applications generally use scene graph representations for the internal management of objects like geometries, light sources and transformations. We present a novel approach, which enables a simple, flexible and universal solution for shadow description and management with scene graph based 3D-applications. We define a fundamental rule, which is adaptable by syntactical and semantical means onto different scene graphs. The fundamental rule we call the "Theory of Shadow Relationships". By means of several syntactical and semantical descriptions it forms the basis for the shadow description and shadow management. The visual rendering of shadows is independent of our solution. The results of our research are used for the development of a new MPEG-4 tool - the "Shadow Node". We show the use of the "Theory of Shadow Relationships" in compliance with the MPEG-4 standard.

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