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It is generally acknowledged that existing computer-aided design systems have inefficient user interfaces. Especially during the concept shape design stage, these systems prove to be cumbersome because of two reasons: (i) they require the usage of twodimensional (2D) input devices, while the designs are typically three-dimensional (3D); and, (ii) CAD systems require the specification of dimensions, which may not be precisely known at the concept stage. To overcome these limitations, this research proposes the use of virtual reality (VR) devices to provide a physically intuitive interface for concept shape creation. The intuitiveness of the interface arises from the use of natural hand gestures and voice commands that emulate the way in which designers discuss concept shapes. In this scenario, the interface between the human and computer plays a central role with respect to usability, usefulness and accuracy. The focus of this research is on using two modalities: (i) hand input; and, (ii) voice driven commands, or a combination of these modalities to accomplish typical CAD tasks. Based on experience with a conventional CAD system, a set of typical CAD tasks are identified. A series of tests are then performed to determine the relative efficiency of the different modality combinations to achieve each task. The interface test results indicate that while voice commands are intuitive in initiating operations such as viewpoint zooming inlout and object creation/deletion, hand inputs are effective in performing spatial tasks such as interactive dimensioning and re-location of shapes. It was also found that a combination of voice and hand input can be used for accomplishing certain tasks more effectively such as, zooming inlout a particular direction (hand,orientation indicates direction and voice is used for indicating zoom inlout operation). Based on the experience with the prototypical system developed it is concluded that voice and hand input are effective ways of building three-dimensional shapes in a virtual reality environment. To verify the efficiency of the VR-CAD interface, sample injection molded parts are built on the current VR-based CAD system and a traditional CAD system, and the times taken to build these parts are compared. The test results indicate that building geometry shapes containing canonical forms, such as block, cylinder, sphere, . .. etc, using a VR interface results in a speedup of five to ten times over traditional CAD systems.

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Despite advances in Computer-Aided Design (CAD) and the evolution of the graphical user interfaces, rapid creation, editing and visualization of three-dimensional (3D) shapes remains a tedious task. Though the availability of Virtual Reality (VR)-based systems allows enhanced three-dimensional interaction and visualization, the use of VR for ab initio shape design, as opposed to ‘importing’ models from existing CAD systems, is a relatively new area of research. Of interest are computer-human interaction issues and the design and geometric tools for shape modeling in a Virtual Environment (VE). The focus of this paper is on the latter i.e. in defining the geometric tools required for a VR-CAD system and in describing a framework that meets those requirements. This framework, the Virtual Design Software Framework (VDSF) consists of the interaction and design tools, and an underlying geometric engine that provides the representation and algorithms required by these tools. The geometric engine called the Virtual Modeler uses a graph-based representation (Shape-Graph) for modeling the shapes created by the user. The Shape-Graph facilitates interactive editing by localizing the effect of editing operations and in addition provides constraint-based design and editing mechanisms that are useful in a 3D interactive virtual environment. The paper concludes with a description of the prototype system, called the Virtual Design Studio (VDS), that is currently being implemented.1.

This paper presents an intuitive and easy-to-use Virtual Reality (VR)-based interface for free-form surface modeling. This work represents further enhancements to the VR-based parametric conceptual shape modeler (COVIRDS – COnceptual VIRtual Design System) currently being developed at the I-CARVE LAB at the University of Wisconsin-Madison. The current research utilizes an intuitive voice and hand input interface to allow editing of NURBS based free-form surface models. The editing scheme allows the designer to utilize higher level ‘primitive’ surface features, in deforming the free-form shape. In addition, interactively specified constraints allow constrained re-location of these surface features giving the designer additional flexibility in designing relatively complex free-form models. Preliminary results based on a prototypical implementation show that the VR-based interface allows free-form models to be created and edited in a much more intuitive way than is possible in conventional CAD systems. Future work will focus on improving the modeling capabilities of the system by integration with a conventional solid/surface modeler.