Raffaele De Amicis, Michele Fiorentino, Andre’ Stork, Giuseppe Monno
Via Bellenzani n.12 Trento
One of the crucial parts during the process of creating and manipulating surfaces is to draw 3D curves. Effective techniques for specifying 3D curves using 2D input devices are been extensively developed, even if the creation of curves is usually limited to a plane but real objects require 3D curves. Nevertheless the main limits of these systems are related to the supplied modelling tools, which usually use the control points for creating and modifying the curves, thus requiring a certain mathematical knowledge and experience to know how to modify these points in order to obtain the desired surface. Conversely virtual reality offers stylists and designers the possibility to immediately sketch and model in 3D, combining the sketching and modelling stages of the design process (1,2). 3D input devices combined with form-descriptive gestures to sketch and deform models three dimensionally and 3D output devices like virtual tables for direct immersive 3D visualization, have the potential to be much more effective because they to allow explore 3D space in a more intuitive and natural way.
SketchAR (our Augmented Reality Computer Aided Styling)-System is one of the first systems, that not only supports three-dimensional modelling in space, but also in augmented realities, while synchronizing visual data with the precise CAD representation of the product. The integration of a modelling kernel, modelling functionality and data export and import capabilities allows SketchAR to make the difference to traditional VR-systems. While in previous works (3,4) we presented several different techniques to generate, in virtual environments, Free-Form surface like coons patches from just one 3D outline stroke, skinned surfaces, Net-Surface, symmetric free-form surfaces by using a virtual palette as a mirror plane, etc. These approaches consist in redesigning the commonly used tools, obviously utilizing a different paradigm that takes advantage of the capabilities offered by new 3D input devices.
The paper presents a very well known technique to generate 3d curve implemented in a virtual and augmented reality environments. By means of this direct manipulative technique designers and stylers can use their natural skills in a digital environments. In this way we have combined the creation and design process, in just one environment. In fact, tape drawing is a wide-spread technique in car-design for the definition of two-dimensional characteristics lines in 1:1 views of the models (Fig.1,2). For this purpose a special duct tape is spread between left and right hand; while the right hand remains above surface and directs the orientation of the curve (tangent to a fixed point), the left hand sets the path of the curve by pressing the tape onto the surface. We have translated this concept into a two-handed, three-dimensional input technique, that allows virtual tape-drawing on a physical mock-up.
The possibility to use a tool that allows the user to specifying 3D curve in a very easy and natural way represent the major contribution of the paper. The combination of the semi-immersive environment with lightweight interaction devices and innovative interaction techniques facilitates intuitive free-form modeling at a VT.
Within the context the european project “SmartSketches”, our AR-CAS-System is in constant progress. Our further efforts will focus on integration of familiar interaction techniques, like drawing on working planes and the ability to edit curves and surfaces.
Proceedings of ADM 1999 International Conference on Design Tools and Methods in Industrial Engineering, Palermo , Italy 2. R. de Amicis, M. Fiorentino, A. Stork, Parametric Interaction for CAD application in Virtual Reality
Environment, Proceedings of ADM 2001 International Conference on Design Tools and Methods in
Industrial Engineering, Rimini , Italy 3. Stork, R. de Amicis: Skectching Freee-Forms in Semi-Immersive Virtual Enviroments, Proceedings of
2000 ASME Design Engineering Technical Conferences, and Computers and Information in Engineering Conference, Baltimore, Maryland, September 10-13,2000 4. Stork, R. de Amicis ARCADE/VT - a Virtual Table-centric modeling system, The Fourth International Immersive Projection Technology Workshop, June 19-20, 2000, Iowa State University, Ames, Iowa,USA