Virtual Environments ’99: Proceedings of the Eurographics Workshop in Vienna, Austria, May 31-June 1, 1999 PDF
Preview Virtual Environments ’99: Proceedings of the Eurographics Workshop in Vienna, Austria, May 31-June 1, 1999
Series Editors w. Hansmann W. T. Hewitt W. Purgathofer M. Gervautz A. Hildebrand D. Sehmalstieg (eds.) Virtual Environments '99 Proceedings ofthe Eurographies Workshop in Vienna, Austria, May 31-June 1, 1999 Eurographies SpringerWienNewYork Univ.-Prof. Dr. MichaelGervautz Dr. DieterSchmalstieg InstituteofComputerGraphics, TechnicalUniversity, Vienna,Austria Dr. lng. Axel Hildebrand ZGDVComputerGraphicsCenter, Darmstadt,Germany Thisworkissubjecttocopyright. Allrightsarereserved,whetherthewholeorpartofthematerialisconcerned,specifically those of translation, reprinting, re-use of illustrations, broadcasting, reproduction by photocopyingmachinesorsimilarmeans,andstorage indatabanks. ©1999Springer-Verlag/Wien Typesetting: Camera-readybyauthors Printedonacid-freeandchlorine-freebleachedpaper SPIN: 10728684 With78Figures ISSN0946-2767 ISBN-13:978-3-211-83347-6 e-ISBN-13:978-3-7091-6805-9 DOI:10.1007/978-3-7091-6805-9 Preface This book contains the scientific papers presented at the SthEUROGRAPHICS Workshop on Virtual Environments '99, which st st was held in Vienna May 31 and June 1 . It was organized by the Institute ofComputer Graphics ofthe Vienna University ofTechnology together with the Austrian Academy of Sciences and EUROGRAPHICS. The workshop brought together scientists from all over the world to present and discuss the latest scientific advances in the field ofVirtual Environments. 31 papers where submitted for reviewing and 18 where selected to be presented at the workshop. Most of the top research institutions working in the area submitted papers and presented their latest results. These presentations were complemented by invited lectures from Stephen Feiner and Ron Azuma, two key researchers in the area of Augmented Reality. The book gives a good overview ofthe state ofthe art in Augmented Reality and Virtual Environment research. The special focus ofthe Workshop was Augmented Reality, reflecting a noticeable strong trend in the field of Virtual Environments. Augmented Reality tries to enrich real environments with virtual objects rather than replacing the real world with a virtual world. The main challenges include real time rendering, tracking, registration and occlusion of real and virtual objects, shading and lighting interaction, and interaction techniques in augmented environments. These problems are addressed by new research results documented in this book. Besides Augmented Reality, the papers collected here also address levels of detail, distributed environments, systems and applications, and interaction techniques. We believe that this selection of outstanding research results yields a book that is valuable not only for scientists, but also for engineers and developers working on applications ofVirtual Environments. Michael Gervautz, Axel Hildebrand and DieterSchmalstieg International Program Committee Peter Astheimer (Germany), Ron Azuma (US), Jean-Francis Balaguer(CH), Massimo Bergamasco (Italy), Mark Bilinghurst (US), David Boyd (UK), David Breen (US), Sabine Coquillart (France), Carolina Cruz-Neira (US), Leonid Dimitrov (Austria), Steve Feiner (US), Bernd Froehlich (Germany), Martin Goebel (Germany), Michitaka Hirose (Japan), Hans Jense (Netherlands), Gudrun Klinker (Germany), He-Dong Ko (Korea), Robert van Liere (Netherlands), Bowen Loftin (US), David Mizell (US), Heinrich Mueller (Germany), Junji Nomura (Japan), Axel Pinz (Austria), Larry Rosenblum (US), Bill Sherman (US), Jaoying Shi (China), Gernot Schaufler (US), Dieter Schmalstieg (Austria), Jose Teixeira (Portugal), Daniel Thalmann (CH), RolfZiegler (Germany) Additional Referees Gerhard Eckel, Christian Faisstnauer, Francois Faure, Andrew Forsberg, Anton Fuhrmann, Gernot Gobbels, Luis Gonvalves, Dieter Koller, Stephan Mantler, Ivan Poupyrev, Greg Welch, Michael Wimmer IX Contents Levels ofDetail C. Andujar, D. Ayala, P. Brunet (Spain): Validity-Preserving Simplification ofVery Complex Polyhedral Solids 1 J. EI-Sana, A. Varshney (USA): View-Dependent Topology Simplification 11 M. Krus, P. Bourdot, A. Osorio, F. Guisnel, G. Thibault (France): Adaptive tessellation of connected primitives for interactive walkthroughs in complex industrial virtual environments 23 Tracking K. Dorfmiiller (Germany): An Optical Tracking System for VRiAR-Applications 33 T. Auer, S. Brantner, A. Pinz (Austria): The integration ofoptical andmagnetic trackingfor multi-useraugmentedreality .43 G. Klinker, D. Stricker, D. Reiners (Germany): An Optically Based Direct Manipulation Interface for Human-Computer Interaction in an AugmentedWorld 53 Rendering ofVirtual,Environments C. Kardassevitch, J. P. Jessel, M. Paulin, R. Caubet (France): Improving the Illumination Quality ofVRML 97 Walkthrough via Intensive Texture Usage 63 M. Wimmer, M. Giegl, D. Schmalstieg (Austria): Fast Walkthroughs with Image Caches andRay Casting 73 D. R. S. Boyd, J. R. Gallop,K. E. V. Palmen, R. T. Platon, C. D. Seelig (UK): Using Virtual Environments to Enhance Visualization 85 Distributed Environments E. Frecon, G. Smith (Sweden, UK): Semantic Behaviours in Collaborative Virtual Environments 95 x R. Behringer, S. Chen, V. Sundareswaran, K. Wang, M. Vassiliou (USA): A Distributed Device Diagnostics System Utilizing AugmentedReality and3DAudio 105 K. Engel, T. Ertl (Germany): Texture-based Volume Visualization for Multiple Users on the World Wide Web 115 Systems and Applications R. van Liere, J. D. Mulder (The Netherlands): PVR - An Architecturefor Portable VR Applications 125 A. Paoluzzi, S. Francesi, S. Portuesi, M. Vicentino (Italy): Rapid DevelopmentofVRML Content via GeometricProgramming 137 D. Verna, A. Grumbach (France): Augmented Reality, the other way around 147 Interaction R. van de Pol, W. Ribarsky, L. Hodges, F. Post (The Netherlands (USA): Interaction Techniques on the Virtual Workbench 157 D. Margery, B. Arnaldi, N. Plouzeau (France): A General Framework for Cooperative Manipulation in Virtual Environments 169 A. Fuhrmann, G. Hesina, F. Faure, M. Gervautz (Austria): Occlusion in Collaborative AugmentedEnvironments 179 Author Index 191 Validity-Preserving Simplification of Very Complex Polyhedral Solids Carlos Andujar, Dolors Ayala, and Pere Brunet Universitat Politecnica de Catalunya, Dept. LSI, Diagonal 647 E-08028 Barcelona, Spain {andujar, dolorsa, pere}01si.upc.es Abstract. In this paper we introduce the Discretized Polyhedra Sim plification (DPS), a framework for polyhedra simplification using space decomposition models. The DPS is based on a new error measurement and provides a sound scheme for error-bounded, geometry and topology simplification while preserving the validity ofthe model. A method fol lowing this framework, Direct DPS, is presented and discussed. Direct DPS uses an octree for topology simplification and error control, and generates valid solid representations. Our method is also able to gener ateapproximationswhichdonotinterpenetratetheoriginalmodel,either beingcompletelycontainedintheinputsolidor boundingit. Unlikemost ofthe current methods, restricted to triangle meshes, our algorithm can deal and also produces faces with arbitrary complexity. 1 Introduction Geometry simplification deals with generation of 3D models that resemble the input model but involve less faces and vertices. A concept closely related is the approximation error -a quantification of the difference between the original model and the simplification. Level of Detail is concerned to the possibility of using different representations of a geometric object having different levels of accuracy and complexity. Multi-resolution models provide severallevel-of-detail representations of a geometric model and have become a powerful tool in many computer graphics applications, including CAD, Virtual Reality and Scientific Visualization, as they ca!l accelerate the handling of complex models by omit ting unessential computation and reducing storage space in visualization [12], [6], transmission over networks [7], query acceleration, collision detection, visi bility analysis and acoustic modeling. Simplification is also used for reducing the verbosityof3D models, adjusting the accuracy to the application's requirements and multi-resolution interactive modeling. 1.1 Solid Simplification vs. Surface Simplification Most of the simplification methods published so far are concerned with a sub problem of geometry simplification which will be called surface simplification. In surface simplification the approximation error is measured by some distance M. Gervautz et al. (eds.), Virtual Environments ’99 © Springer-Verlag/Wien 1999 2 defined on the points on the surface, regardless of the enclosed volume, if any. We introduce a new approach for the geometry simplification problem, the solid simplification (Table 1). Solid simplification measures the error using the points inside the solid, and hence it has more freedom for modifying the geometry and the topology (genus and shells). 1.2 Previous Work on Surface Simplification Most of the current simplification methods are devoted to triangle meshes. An approach is incremental if simplification proceeds through a sequence of local boundary updates which reduce the face count. Different local operators have been proposed, such as vertex removal [13], edge collapse [7] and face removal. Current methods are not suitable for the simplification of solids because they produce invalid solids, they are unable to simplify topology, or the error is not bounded. A simplification method for the special case oforthogonal polyhedra is pre sented in [4] and extended for general polyhedra in [1]. Unfortunately, both methods usually increase the number of components of the solid. Another ap proach based on sampling and low-pass filtering is presented in [3], but it does not provide a suitable bound for the error. 1.3 Contribution In this work we introduce the Discretized Polyhedra Simplification, a framework for polyhedra simplification (Section 2) and a new algorithm, Direct DPS (Sec tion 3), that generates error-bounded solid approximations, and is capable of reducing the topology of the input solid. The results and conclusions are shown in Section 4. Table 1. Surface simplification vs. Solid Simplification 3 2 Discretized Polyhedra Simplification The DPS framework models a family of simplification methods which have in common the use of an intermediate space decomposition scheme to generate a multi-resolution family of solid representations. The DPS framework involves five components: a decomposition scheme, an error metric, and discretization, reconstruction and face reduction processes. The DPS pattern (Figures 1and 3) shows the integration ofthese components. DecompositionScheme Aspacedecompositionschemeallowssoundtopology simplification. Only regular decompositions, such as voxelizations and maximal division classical octrees (MDCO) [5] are ofinterest for uniform error control. Error Metric Almost all the simplification methods use a metric based on the points of the surface; such a metric is called on-metric. On-metrics are not appropriate for solid simplification since they limit the topology reduction. The DPS framework is based on a new approach for error measurement, the in metrics, i.e., basedon the points inside thesolid. Symmetrically, out-metrics are based on the points outside the solid. The following distances represent these three approaches: In-Hausdorff distance is the symmetric Hausdorff distance defined over the points inside the volume enclosed by the solids. A solid P' is said to approximate P within a bound c: iff VpEP 3p'EP' Idist(p,p') <c: and Vp'EP' 3pEP Idist(p,p') <c:. (1) The .on-Hausdorff (resp. Out-Hausdorff) is the symmetric Hausdorff dis tance defined over the points on the boundary (resp. outside the solid). The In-Hausdorff is a good quantification of the difference between two solids and allows topology simplification (especially shell reduction). Discretization The discretization process consists on the conversion of the input solid P into a multi-resolution family of decomposition representations. The discretization proceeds through a space subdivision producing the more accurate model followed by iterative grouping of adjacent cells creating coarser representations. Grouping in octrees is achieved by pruning the deepest level. --1 -1 ~~ ~/" 0, HI"(,Ol"tmctioll I'D, FaceRcductioll --1 ~/'tl 0, I Ih'<'OI.<tn!(·rioll PO, I FlU'" HI'<luCliulI I' Dis:n:·tizntiOll -1 ~ --j ~ 00 R{'('OlIstmctiulI PDo FlU'(,Hcdul"lion 1'0 Fig.1. The DPS framework. Ok stands for a 2kx2kx2k division ofthe space
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