DesignSpace: A Manual Interaction Environment for Computer Aided Design William L. Chapin, Timothy A. Lacey, and Larry Leifer Virtual Space Exploration Lab Center for Design Research, Stanford University 560 Panama St., Stanford, CA 94305-2232, USA
[email protected],
[email protected],
[email protected] ABSTRACT
DesignSpace is a computer-aided-design (CAD) system that facilitates dexterous manipulation of mechanical design representations. The system consists of an interactive simulation programmed with a seamless extended model of the designer's physical environment and driven with continuous instrumentation of the designer's physical actions. The simulation displays consistent visual and aural images of the virtual environment without occluding the designer's sensation of the physical surroundings. Developed at Stanford University's Center for Design Research (CDR), DesignSpace serves as an experimental testbed for design theory and methodology research. DesignSpace includes significant contributions from recent CDR development projects: TalkingGlove, CutPlane, VirtualHand, TeleSign, and VirtualGrasp. The current DesignSpace prototype provides modeling facility for only crude conceptual design and assembly, but can network multiple systems to share a common virtual space and arbitrate the collaborative interaction. The DesignSpace prototype employs three head-tracked rear projection images, head-coupled binaural audio, hand instrumentation, and electromagnetic position tracking. KEYWORDS
CAD, virtual environment, dexterous manipulation, interactive simulation, presence, spatial acoustics, manual and gestural communication, teleconference, collaboration. INTRODUCTION
Technology developments for CAD have traditionally influenced human-computer interaction (HCI) in general computing. Many interface technologies and interaction methods prevalent now for general computing (graphical displays, pointing devices, menus, tools, direct manipulation, etc.) were first prevalent in CAD. Evolution in HCI has also broadened opportunities for CAD. Engineers immediately embraced early two-dimensional (2D) CAD, emulating its paper equivalent, despite its 1D, commandline interface requiring numerical and textual input before visualization. Other designers such as architects and graphic artists resisted computer tools until the 2D
pointing device shifted the paradigm and allowed visualization without explicit numerical references. 3D CAD faces similar resistance today while workstation systems channel the design interaction through one and two dimensional interfaces. A design tool should maintain full dimensionality in the design process and not subject the design to unnecessary constraints in the communication between designers, the design media, and the final realized artifact. DesignSpace embraces this ideal by providing facilities for interactive simulation, dexterous manipulation, and remote collaboration. BACKGROUND
CDR was founded in 1983 as an industry-academia collaborative and interdisciplinary R&D center to improve the engineering and product design processes. The Center accepts design problems from industry and government, and confronts them with creative design teams, for the purpose of design process observation and study, experimental design practice, and new design tool development. A long-term CDR goal is to aid the design process so that problem complexity does not impede creativity, design knowledge reuse, and human skill. CDR researchers and designers collaborate on projects to study the design process, to develop devices and interfaces to better map manual skills to data operations, to experiment with alternative means of design knowledge storage and retrieval, and to investigate design tool effectiveness. DesignSpace encapsulates technologies from several CDR projects within a conceptual design environment context to serve as a testbed for evaluating their effective application. PROJECT GOALS
The initial goal of the DesignSpace project was to integrate the unique technological advances from several closely related CDR projects in the context of a conceptual design tool application. The DesignSpace application was designed to highlight the double relationship of the usefulness of these technologies to computer based design media and of computer based design media to designers. For the latter, DesignSpace facilitates remote collaboration, with very little initial attention paid to many better known benefits of CAD such as scalability, precision, storage, and reuse. While the system was to be a testbed to evaluate the new technologies in application context, DesignSpace itself has become a research project to test theories of manual skill in design, manual communication in collaboration, and natural human-computer interaction.
RELATED CDR PROJECTS
Several CDR projects form the basis for DesignSpace: • TalkingGlove [3] -- an assistive communication device for nonverbal deaf individuals, which recognizes American Sign Language (ASL) fingerspelling to generate text or synthesized speech. Core to the TalkingGlove system is an instrumented glove and neural net recognition algorithm for mapping dynamic hand formations into a digital command stream. Virtual Technologies developed the patented technology into the Virtex CyberGlove hand instrumentation system. • CutPlane [2] -- a solid-modeling interaction tool for a standard workstation, eliminating the need for orthonormal projections, command line input, and menu command selection, while providing continuous 3D access. • VirtualHand (Chapin and Kramer) -- a dynamic simulated hand model driven by an instrumented glove. • VirtualGrasp (Chapin and Kramer) -- an extension of the VirtualHand model to enable force closure and contact control of 3D virtual objects. • TeleSign [1] -- a collaborative design effort between CDR and the Center for the Study of Language and Information, leveraged from the TalkingGlove and VirtualHand projects to develop a system for visual expression and manual communication. The TeleSign system empowers two remote individuals to communicate with visible gestures through a shared virtual environment across standard low-bandwidth telephone channels. EXHIBITED TECHNOLOGIES
DesignSpace exhibits six key emerging technologies, demonstrating either advances or unique implementations by CDR: dexterous manipulation, manual communication, virtual presence, telecommunication, interaction arbitration, and auditory display. Dexterous manipulation in a virtual environment is built upon several equally important components, including high precision instrumentation in both state and time, modeling and control of an anthropometric virtual manipulator, physical modeling of virtual object interaction, and real-time feedback to the operator. The dexterous manipulation technology in DesignSpace evolves directly from the VirtualGrasp project. Manual communication in a virtual environment encompasses gestures for both human and machine interpretation. The VirtualHand and TalkingGlove projects supply the respective gesture technology for the DesignSpace system. Virtual presence is the synthesis of a perceptual consistency that convinces users that either they are immersed in another space or that computer generated artifacts exist in the physical space (illusion). By occluding aural and visual perception of the physical space with a headmounted display (HMD), immersion needs only a consistent synthetic model to be achieved. In contrast, the illusion of virtual object presence in a physical space, which DesignSpace attempts to create, requires a consistent synthetic model that also perfectly complements the physical space. The telecommunication technology, borrowed from TeleSign and further developed for DesignSpace, not only exchanges remote information, but encodes it with spatial data within a low bandwidth protocol for standard telephone line transmission. Since each station maintains
identical local clients, DesignSpace preserves low latency and virtual presence, but requires interaction arbitration to resolve conflicts with late remote data. Auditory display technology models the acoustic properties of the physical space and encodes synthetic and remote auditory information with spectral and temporal cues that are perceptually consistent with the surroundings. IMPLEMENTATION
DesignSpace is implemented in hardware-independent C++, with a client/server protocol that is independent of the device configuration. Obviously, for example, a client without hand instrumentation data could not interpret dexterous manipulation, but all other features would remain active and manipulation could be facilitated with a substitute device, such as a mechanical probe or 3D mouse. In addition to a local client process, each DesignSpace station runs an interface server configured to drive its particular employment of computational, input, and display hardware. Each server renders its particular viewpoint to the best quality afforded on the local hardware. The current prototype system runs on low cost Intel i486/Pentium systems under DOS, for low level access to a wide variety of I/O devices and deterministic control of all processor cycles. DesignSpace tracks body positions with Polhemus electromagnetic receivers and hand poses with Virtex CyberGlove instrumentation. An i860 based 24-bit graphics pipeline from Division Ltd. processes each view. Up to three views can be configured for orthogonal fixedplane rear projections (depth perception via head-tracked motion parallax), with option for a head-coupled stereo view pair with a Fakespace BOOM. Acoustetron subsystems by Crystal River Engineering synthesize and spatialize audio content. FUTURE DIRECTIONS
Architecturally, the client and server processes may be split onto respective processors with shared memory to avoid time slicing. A tabletop fixed-plane image is necessary. For depth perception, users have requested more evaluation of stereo vision, thus far abated since stereo devices necessarily occlude the surroundings. Tactile and haptic displays are planned for evaluation in DesignSpace. REFERENCES
1.Chapin, W., Kramer, J., Haas, C., Leifer, L., and Macken, E., TeleSign: A Sign Language Telecommunication System. In Proc. Johns Hopkins National Search for Computing Applications to Assist Persons with Disabilities, February 1-5, 1992, pp. 2-4. 2. Edwards, L., Kessler, W., and Leifer, L., The Cutplane: A Tool for Interactive Solid Modeling, ACM Special Interest Group on Computer and Human Interaction (SIGCHI), 20(2):72-77, October 1988. 3.Kramer, J. and Leifer, L., The Talking Glove: An Expressive and Receptive "Verbal" Communication Aid for the Deaf, Deaf-Blind and Nonvocal. In Proc. Ann. Conf. Computer Tech/Spec Ed/Rehab, Cal State Univ., Northridge, CA, 1987, pp.335-340.
