GEOMETRIC MODELING IN MULTI-MODAL, MULTI-SENSORY VIRTUAL ENVIRONMENT

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1 GEOMETRIC MODELING IN MULTI-MODAL, MULTI-SENSORY VIRTUAL ENVIRONMENT Rajarathinam Arangarasan Ph.D. Student Chi-Cheng Chu Doctoral Candidate Tushar H. Dani Project Engineer, Automated Analysis Corp., Ann Arbor, MI. Xiaochun Liu Research Staff Rajit Gadh Professor Department of Mechanical Engineering University of Wisconsin - Madison Wisconsin, USA gadh@engr.wisc.edu Phone: (608) ABSTRACT: Conventional Computer Aided Design (CAD) systems usually use 1D and 2D input/output (I/O) devices for 3D shape modeling. These devices require mapping processes between I/O devices and the modeling space, resulting in a nonintuitive, complicated design interface and low throughput between the designer and the system. To overcome these deficiencies a new approach for geometric modeling in a multi-modal multi-sensory Virtual Environment (VE) has been developed. This system provides an intuitive and natural way of designing using hand motions, gestures and voice commands. This approach also allows the designer to be immersed in a stereoscopic display and synthesized sound output, which enables high throughput between the designer(s) and the system and paves the way for a collaborative design environment. This system also has been integrated with a commercial CAD system to combine the advantages of conventional CAD systems with Virtual Reality (VR) techniques. KEYWORDS: virtual environment, virtual prototyping, concept design, detailed design, parametric modeling, collaborative virtual environment. INTRODUCTION: Despite the advances in the field of CAD and solid modeling, shape modeling in the conventional CAD systems remains a tedious and time-consuming task. Most of the conventional CAD systems generally use 1D and 2D I/O devices for modeling in 3D geometric space, which results in a non-intuitive design interface, unnecessary steps in modeling and difficulties in visualizing the complex 3D shapes correctly. Also, these CAD systems require expertise and in-depth understanding

2 of the modeling process and the system itself, thus increasing the modeling time and learning time considerably. Due to the nature of the conventional CAD systems interface, only one I/O device (e.g. either keyboard or mouse and monitor) are effectively used at a time. Though the designer (human being) has the built in capability to communicate in a multi-modal, multi-sensory interface, the restrictions inherent in CAD systems leads to a considerable waste of human resources. Moreover, most CAD systems are designed such that only one person can use them effectively at a time, thus making the collaboration process a tedious task. To overcome these problems a new methodology has been developed for concept shape design, detailed shape design and parametric surface modeling in a Virtual Environment. This paper discusses the COnceptual VIRtual Design system (COVIRDS), Detailed Virtual Design System (), parametric freeform surface modeling in VE and the hardware setup of the Virtual Design System. multi-sensory interface. The human sensories used in VR-CAD systems are mouth, fingers, hands, head, body, eyes, skin and ears. CONCEPTUAL VIRTUAL DESIGN SYSTEM (COVIRDS): Concept design is the phase of product design in which the overall functionality and shape of the product is determined. Details such as exact dimensions, positioning and tolerances are dealt with in the detailed design phase, rather than the concept design phase, allowing the designer more freedom in determining the features of the product. Most of the current CAD systems require the designer to define the model very precisely, and in many cases they do not allow the design to be easily modified later in the process. VR is an ideal tool for conceptual design, which requires a minimal amount of user input to create the concept shape. Through stereoscopic display it allows much-improved visualization of the design. DIFFERENCES BETWEEN CONVENTIONAL CAD SYSTEMS AND VR-CAD SYSTEMS: Figure-1 shows the mapping process in conventional CAD systems. The human sensories used in these systems are hands, fingers and eyes. 1D, 2D 3D Voice Mouth (Speech) Gesture Fingers (Haptic) 3D Motion Hands, head, body (3D Position Tracking) Stereoscopic Display 1D-space 2D-space I/O Devices Keyboard, mouse and monitor 2D 3D Geometric Space Eyes (Visual) Force Feedback Skin (Tactile) 3D-space Synthesised 3D-Sound Fig. 1 - I/O Interface in conventional CAD systems Figure-2 shows the interface in, where mapping processes are eliminated and high throughput between the designer and the system is achieved by multi-modal and Ears (Auditory) I/O Devices Modeling space Fig. 2 I/O Interface in

3 COVIRDS consists of two basic components: (i) user interaction and (ii) shape representation via virtual modeller. A multi-modal interface using voice and hand [3], [4] has been used for an intuitive input interface. To meet the requirement of real time interaction and editing of geometric shapes, a dual graph representation [5], [6] and D&S graphs (Design intent and Shape modelling graphs) are used in the virtual modeller. In this system the geometric primitives such as spheres, block, cylinder, wedges etc. are efficiently represented using D&S graphs to design and edit concept shapes. Since the data at the solid modeling kernel level cannot be updated in real-time (i.e. >30fps for mono and >60fps in stereo mode) while editing the geometry, a new concept called Liquid Features is introduced. Liquid features can be edited/modified in real-time and once the operation on these features is completed it updates the data in the solid modeling kernel database. Spatial Recognition CAD System DETAILED VIRTUAL DESIGN SYSTEM (): Detailed design involves the development of a detailed model of the product. This includes defining features, determining their dimensions, tolerances, materials, manufacturing processes, etc. Almost all CAD systems are developed for detailed design. But due to the interface and interaction techniques, they make shape modeling a tedious and nonintuitive task. The nature and architectural development of the provides higher dimensional, multi-modal, multi-sensory interaction between the designer and the system, thus making the designing process easy and intuitive. DESIGNER(s) Gesture Recognition Voice Recognition Stereoscopic Display Auditory Feedback Command Parser Engine Graphics Engine - Database - (e.g.) is an intermediate software layer that resides between the hardware layer and the commercial CAD system. command parser module efficiently synchronises the multi-modal, multi-sensory I/O interface between the several I/O devices and the CAD system. Due to the architectural design of the conventional CAD systems interface, the sequence of operations is generally unidirectional. Since supports multimodal, multi-sensory I/O, it allows the designer(s) to perform multiple operations simultaneously, for example changing the dimension of a feature while changing the orientation of the part using another mode of input. Designer(s) Space Hardware Layer CAD Kernel / Application Fig. 3 System Architecture of

4 Fig. 4 Model at intermediate stage. Liquid Feature" shown in red/yellow shade SYSTEM SETUP: Hardware: - Intergraph Realizm II (Rendering Engine) - Ascension flock of birds (3D tracking) - 5th Dimension Data glove (Hand gestures) - IBM microphone set (Voice input) - Electrohome projector (Stereoscopic projection) - CrystalEyes emitter and glasses (Stereoscopic viewing) - Sony speaker (Synthesized 3D sound output) Software: - WorldToolKit library (Graphics library) - Visual C++ (Compiler) - SolidWorks-99 (Commercial CAD system) - IBM Viavoice (Voice recognition) Fig. 5 Completed model created in Parameters Conventional CAD Systems COVIRDS Fig. 6 Parametric Surface Model Concept design No Yes Yes Detailed design Yes No Yes Parametric modeling Yes Limited 1 Yes Intuitive design steps No Yes Yes Industry standard CAD representation Yes Limited 2 Yes 3 Multi-modal input No Yes Yes Multi-sensory interface No Yes Yes Immersive display No 4 Yes Yes Collaborative design No No 4 Yes 1 Primitive based parametric modeling 2 Maintains its own representation and file format 3 Uses the same representation as that of the underlying CAD system 4 Allows only for viewing, not in editing mode Table 1 Feature comparisons between conventional CAD Systems, COVIRDS and Fig. 7 Multiple Designers collaborating in Virtual Environment

5 SUMMARY: This paper presents researches about a new paradigm developed for concept and detailed shape modeling in a multimodal, multi-sensory Virtual Environment. The development of Conceptual Virtual Design System (COVIRDS), Detailed Virtual Design System () and the hardware set-up of Virtual Design System is described. ACKNOWLEDGEMENTS: The authors acknowledge the support of the National Science Foundation for the NSF Career Grant No. DMI and NSF Research Equipment Grant No. DMI REFERENCES [1] R. A. Bolt, and E. Herranz, Two- Handed Gesture in Multi-Modal Natural Dialog, Proc. of ACM Symp. on UIST, November, 1992 pp [2] Christoph M. Hoffman: Geometric and Solid Modeling, Morgan Kaufmann publichers Inc., [3] C.-C. Chu, T. H. Dani and R. Gadh, Multimodal Interface for a Virtual Reality Based CAD System, CAD Journal, Elsevier Publications, Vol. 29, No.10, pp , [4] C.-C. Chu, T. H. Dani and R. Gadh, Evaluation of Virtual Reality Interface for product shape design, IIE Transactions Special Issue on Virtual Reality, vol. 30, no. 7, pp , July, [5] T. H. Dani, R. Gadh, Creation of concept shade designs via a virtual reality interface, CAD Journal, Elsevier Publications, Vol.29, No.8, pp , [6] T. H. Dani and R. Gadh, A Dual Graph Representation within a Geometric Framework supporting Shape Design in a Virtual Reality Environment, Technical Report, I-CARVE Lab, Mechanical Engineering Department, University of Wisconsin Madison, [7] T. H. Dani, R. Gadh, Chapter-14: Virtual Reality A new Technology for the Mechanical Engineer, The Mechanical Engineers Handbook, 2 nd Edition. John Wiley & Sons, 1998, Editor: Myer Kutz. [8] Rakesh Gupta, Daniel Whitney and David Zelter, Prototyping and Design for Assembly analysis using Multimodal virtual environments, CAD Journal, Elsevier Publications, Vol. 29, No. 8, pp , [9] Mark R Mine, ISAAC: a meta-cad system for Virtual Environments, CAD Journal, Elsevier Publications, Vol. 29, No. 8, pp , [10] Martti Mantyla: An Introduction to solid Modeling, Computer science press, [11] Michael E. Mortenson: Geometric Modeling, John Wiley & sons, [12] Michael F. Deering, HoloSketch: A Virtual Reality Sketching / Animation Tool, ACM Transactions on Computer- Human Interaction, Vol 2, No. 3, pp , [13] Rajarathinam A., Tushar H. Dani, Chi- Cheng Chu, Rajit Gadh, Virtual Design Technology and Applications, SME Conference at U.S. Army Tank-Automotive and Armaments Command (TACOM) Facility in Waren (Detroit), Michigan, Nov 3-4, [14] Shumin Shai, User Performance in Relation to 3D Input Device Design, Computer Graphics, pp 50-54, November [15] A. Stork, M. Maidhof, "Efficient and Precise Solid Modeling using a 3D Input Device," Proc. of the Fourth Symposium on Solid Modeling & Applications, Atlanta, GA, May 14-16, 1997, pp

6 IMAGE GALLERY (Models created using the COVIRDS, )