Sketching Free-Forms in Semi-Immersive Virtual Environments
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In spite of the widely used sophisticated software tools for mechanical design, serious difficulties are encountered in the styling phase of the design process when free-form surfaces (shortly free-forms) have to be modelled. In this paper we extend the ideas of Sachs19 pioneering 3-Draw which allowed curve sketching in 3D space in several ways: we support the creation of NURBS surfaces (not only curves), we use a semi-immersive environment centered around a table-like stereoscopic backprojection display (also know as Virtual Table or Responsive Workbench) and we give the user an immediate preview while he sketches free-form surface. This combination of features makes our approach unique in comparison to similar systems. Some of them only work on polyhedral models and others are restricted to indirect 3D interaction with control points. Our approach follows the Walk-Up VR concept: the user can just step in front of a Virtual Table and work on his task intuitively.
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Sketching Free-Forms in Semi-Immersive Virtual Environments
- 1. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis Sketching Free-Forms in Semi-Immersive Virtual Environments Raffaele de AmicisRaffaele de Amicis André StorkAndré Stork OliverSchimpkeOliverSchimpke FraunhoferInstitute forComputerGraphics (IGD)FraunhoferInstitute forComputerGraphics (IGD) Department forIndustrial ApplicationsDepartment forIndustrial Applications Rundeturmstraße 6Rundeturmstraße 6 64283 Darmstadt64283 Darmstadt http://www.igd.fhg.de/igd-a2/http://www.igd.fhg.de/igd-a2/
- 2. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis Overview • Introduction • Related work • Hardware and system set-up • Free-form sketching methods – Coons patches with just one stroke – Skinning with immediate preview – Net-surfaces – Symmetric surfaces – Trimming • Conclusions and future work
- 3. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis • Difficulties are encountered in the styling phase of the design process when free-form surfaces (shortly free- forms) have to be modelled. • The styling phase is still determined by clay models, only later in the process CAS systems are used. • The industry is looking for easy to use fee-form sketchers in virtual environments that narrow the gap between human beings and computer. Introduction
- 4. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis • Starting point: There are well known free-form surface concepts (Coons patches, skinning, etc.) but they require much knowledge on the user’s side. • Main questions: • How to build up an intuitive user-interface to these free-form surface modelling techniques ? • How to map the sketched data to the algorithms behind these techniques ? Introduction
- 5. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis • Prerequisites: • We want to follow a line-oriented approach where the user sketches lines in free space. This follows the way designers think and work, especially those in the automotive industry. • We don’t want to cope with control points: the user shall be enabled to draw a surface in free space. • We want to generate surfaces that can be post-processed by commercial tools. Introduction
- 6. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis Related Work • 3-Draw: A tool for designing 3D shapes. E. Sachs, A. Roberts, and D. Stoops. No visual correspondence • Free-Form Surface Design in a Virtual Environment. T. H. Dani, L. Wang, R. Gadh. Interaction with control points • Surface Drawing, Schroeder et al. Drawing polygonal structures in 3D at VT using a glove • Multiple-Points Constraints based Deformation for Free-Form Surfaces. J.M. Zheng, K.W. Chan, I Gibson. Deform sketched regions with 2D input • etc.
- 7. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis Virtual Pad Object underconstruction Pen Transparent physical pad Userat the Virtual Table Hardware setup
- 8. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis Why Virtual Tables? • direct 3D input in the space over the tabletop • lightweight interaction devices • integratable in the daily work process (much better than HMDs, CAVEs, gloves) • support of the ‚Walk-Up VR‘ concept Hardware setup
- 9. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis Free Form Surface Sketching • Coons Patches • Net-Surfaces • Skinned Surfaces • Trimming • MirrorMode
- 10. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis Coons Patches fromonly one outline stroke 3Doutline stroke with shadow projection onto virtual walls • Coons patches are defined by two pairs of curves, one in u and v direction respectively. • To ease the input process, we want to derive them fromjust one outline stroke. • BUT, how to split it up?
- 11. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis Coons Patches fromonly one outline stroke Splitting contourby WC bounding box Splitting contouruniformely in u,v space Splitting contourby min. bounding box
- 12. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis Coons Patches fromonly one outline stroke
- 13. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis Skinned Surfaces • are usually defined by a set of similarly oriented curves • by laying a ‚skin‘ over the curves the surface is defined • usually the user has to input the curves and has no impression of the final surface until the interpolation is done To overcome these problems, we introduced: • preview by polygonal visual feedback • adaptive point insertion technique The potential of skinned surfaces is better accessible.
- 14. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis Skinned Surfaces with immediate feedback
- 15. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis Net-Surfaces • allow to bettercontrol the innershape of a free-form surface • but the approximation algorithmwants the curves directed and ordered which hinders the user’s flexibility when inputing the curves 3 4 1 6 1 2 5 1 1 1 This is how the userwants to input the curves (any order, any direction) Sketch of a carbody using a net-surface
- 16. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis Net-Surfaces • so, we determine the plane ‘over’ which the curves are defined • sort the curves along the majordirections of the plane (u and v) • and redirect them, so that point in the same direction • finally, we feed the net-surface approximation algorithmto generate the free-formsurface Kurvennetz Vektoren zwischen projizierten Kurven- endpunkten Ebene mit max. Summe der Länge vectors between projected curve endpoints curve net plane with max. sum of vector lengths Sorting algorithm Case that is not handled correctly by oursorting
- 17. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis Net-Surfaces
- 18. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis MirrorMode A symmetric coons patch using the pad as a mirror • Many industrial products are symmetric. • Instead of drawing only one half and mirrorit afterwards, we designed a two-handed technique that creates a symmetric surfaces while drawing the curve(s) by using the palette as virtual mirror.
- 19. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis Trimming • Up to now, we used direct 3Dinteraction, fortrimming this is hardly possible. • Therefore, this time the pen sends a ray into the scene to define the trimcurve.
- 20. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis Subtractive Sweeping ... ... is not exactly a free-formsurface sketching technique, but a means to shape volumes by removing (oradding) material. A real-time rendering techniques immediately shows the result.
- 21. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis • Intuitive free-formsketching techniques • Releasing the userfrommathematical knowledge • Characteristic lines • 2-handed interaction with pad and pen • Direct 3Dinteraction techniques and 3Dvisualization • Correspondence between hand movement and visual feedback • Walk-up VR-concept • Lightweight interaction devices Conclusion
- 22. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis • Free Formdeformation techniques (in combination with the palette), • Users studies and discussion groups, • Evaluation of alternative input devices and tracking technology, … to render the Virtual Table to its full potential as a modeling workspace. Future Work
- 23. Fraunhofer Institut Graphische Datenverarbeitung IGD-A2 André Stork OliverSchimpke Raffaele De Amicis yourattention !yourattention ! Thanks forThanks for