A Constraint Manager for Intuitive and Precise Solid Modelling in a Virtual Reality Environment

The absence of efficient constraint management facilities when interacting with virtual objects is one of the major limitations of current virtual reality systems for CAD applications. Without constraint management facilities, it is difficult to perform precise interactions with today's 3D input devices and precise solid modelling in the VR environments cannot be ensured. In this paper, a constraint manager is presented for intuitive and precise solid modelling in the VR environment. This constraint manager generates constraint-based 3D direct manipulations for precise solid modelling through incorporating constraints into the VR environment. Constraint-based manipulations are realized by allowable motions for precise 3D interactions in the VR environment. The allowable motions are represented as a mathematical matrix for conveniently deriving allowable motions from constraints. A procedure-based degree-of-freedom incorporation solver for solving 3D constraints is presented for deriving th allowable motions. A rule-based constraint recognition engine is developed for implicitly incorporating constraints into the VR environment.