This paper presents a constraint-based methodology for product design with advanced virtual reality technologies. A hierarchically structured and constraint-based data model is developed to support product design from features to parts and further to assemblies in a VR environment. Product design in the VR environment is performed in an intuitive manner through precise constraint-based manipulations. Constraint-based manipulations are accompanied with automatic constraint recognition and precise constraint satisfaction to establish constraints between objects, and are further realized by allowable motions for precise 3D interactions in the VR environment. The allowable motions are represented as a mathematical matrix and derived from constraints between objects by constraint solving. A procedure-based degrees-of-freedom combination approach is presented for 3D constraint solving. A rule-based constraint recognition engine is developed for both constraint-based manipulations and implicitly incorporating constraints into the VR environment. An intuitive method is presented for recognizing pairs of mating features between assembly components. Examples are presented to demonstrate the efficacy of the proposed methodology.

This paper presents a novel approach to integrate VR and CAD for virtual assembly, namely, CAD linked virtual assembly environment. Compared with most existing VR and CAD integration approaches, the proposed approach is a kind of external integration with a CAD system through automation interfaces. A novel hybrid virtual assembly model is developed in this paper to support this external integration. It works as a combinator that links the precisely represented design dataset in CAD models and the corresponding hierarchically structured virtual assembly dataset in the VR application. With this model, a framework has been developed to embed and apply CAD assembly constraints on the virtual assembly structure. Constraint-based manipulation is then implemented in the virtual assembly environment. Moreover, with this framework, advanced computations, such as runtime DOF determination, disassembly directionality computation, and assembly/disassembly sequence generation, which rely on assembly constraint information, can be feasibly integrated into the virtual assembly application with much less effort. The approach is also more practical in terms of implementation due to two advantages: (1) It does not require the implementation of a complicated support for solid modelling in the virtual assembly application. (2) A virtual assembly environment can be automatically created and updated from the linked CAD models.

This 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.

Abstract This 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.

This paper presents a constraint-based methodology for intuitive and precise solid modelling in a virtual reality (VR) environment. A hierarchically structured and constraint-based data model is developed to support solid modelling in the VR environment. A constraint reasoning engine is also developed to automatically deduce allowable motions for precise constraint-based 3D manipulations. A prototype system of product modelling has been successfully developed, and experimental results demonstrate the advantage of precise solid modelling through constraint-based manipulation in virtual environments.

A methodology for solid modelling in a virtual reality environment

A hierarchically structured and constraint-based data model for intuitive and precise solid modeling in a virtual reality environment