A behavioral scene graph for rule enforcement in interactive virtual assembly sequence planning
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abstract
Most VR development toolkits are proprietary in nature, which make them difficult to interoperate across platforms. Interoperatibility involves synchronizing elements in addition to geometric data, such as object behavior and animation patterns. The commonly used method of data representation in virtual environment is by using a scenegraph structure. The scenegraph is not able to capture the manufacturing attributes and behavior of objects, such as rule enforcement and status information. This leads to the execution of infeasible operations in the virtual environment. A Virtual Manufacturing Lattice (VML) structure is described here to address the identified limitations of the scenegraph structure for application in virtual manufacturing. The VML is a multiple hierarchy structure, which each node in the hierarchy representing the objects in the virtual environment. The VML is used to augment the scenegraph structure to encapsulate object characteristics at the node level. The nodes are represented by a 4-tuple structure C,R,T,E where C is the composition element used to represent object geometry, location and material properties, R is the precedence relationship element used to describe precedence rules between other nodes, T is the trajectory element used to describe motion parameters and interfacing with external subsystems, and E is the event control list used to describe the state of the object. The R and E elements of the 4-tuple are used in enforcing the rules in virtual assembly planning and prohibit the execution infeasible operations in the virtual environment.
