Virtual modelling of solid objects with constraint-based manipulations

AbstractThis paper presents an intuitive approach to precise solid modelling in virtual reality environments. A hierarchically structured model is established to handle the tasks of object definition, object creation, and object rendering with an integrated data structure. Constraints are organized at different levels on different objects and are embedded in the data structure. A constraint reasoning engine is developed to automatically determine allowable motions for precise manipulation of virtual objects with online assistance from constraints. Examples are presented to demonstrate the advantage of precise solid modelling through constraint-based manipulations in virtual environments.