Visibility, problems, techniques and applications Course Notes for SIGGRAPH 2000 New Orleans, Louisiana July 2000 Organizer: Daniel Cohen-Or Tel-Aviv University Speakers: Yiorgos Chrysanthou UCL University of London George Drettakis iMAGIS-GRAVIR/IMAG Claudio´ T. Silva AT&T Labs-Research 1 Abstract Visibility determination, the process of deciding what surfaces can be seen from a certain point, is one of the fundamental problems in computer graphics. Its importance has long been recognized, and in network-based graphics, virtual environments, shadow determination, global illumination, culling, and interactive walkthroughs, it has become a critical issue. This course reviews fundamental is- sues, current problems, and unresolved solutions, and presents an in-depth study of the visibility algorithms developed in recent years. Its goal is to provide students and graphics professionals (such as game developers) with effective techniques for visibility culling. Schedule 1:30 – 1:50 Introduction to visibility Cohen-Or 1:50 – 2:50 Object-space visibility Silva 2:50 – 3:30 Image-space visibility Chrysanthou 3:30 – 3:45 Break 3:45 – 4:15 From-region visibility Cohen-Or 4:15 – 4:45 The visibility complex Drettakis 4:45 – 5:00 Final questions (All speakers) 2 Speaker Biographies Daniel Cohen-Or Computer Science Department School of Mathematical Sciencees Tel-Aviv University, Ramat-Aviv 69978, Israel E-mail: [email protected] Daniel Cohen-Or is a senior lecturer at the Department of Computer Science since 1995. He received a B.Sc. cum laude in both Mathematics and Computer Science (1985), an M.Sc. cum laude in Computer Science (1986) from Ben-Gurion University, and a Ph.D. from the Department of Computer Science (1991) at State University of New York at Stony Brook. He has been a lecturer at the Department of Mathematics and Computer Science of Ben Gurion University in 1992-1995. He is on the editorial advisory board of the international Computers and Graphics journal. He is the Program Co-chair of the symposium on volume visualization to be held in the year 2000. He is a member of the program committees of several international conferences on visualization and computer graphics, including IEEE Visualization and Eurographics. Between 1996-8 he served as the Chairman of the Central Israel SIGGRAPH Chapter. Dr. Cohen-Or has a rich record of industrial collaboration. In 1992-93 he developed a real-time flythrough with Tiltan Ltd. and IBM Israel for the Israeli Air Force. During 1994-95 he worked on the development of a new parallel architecture at Terra Ltd. In 1996-1997 he has been working with MedSim Ltd. on the development of an ultrasound simulator. His research interests are in Computer Graphics, and include rendering techniques, client/server 3D graphics applications, real-time walkthroughs and flythroughs, volume graphics, architectures and algorithms for voxel-based graphics. Yiorgos Chrysanthou Department of Computer Science UCL University of London Gower Street, London WC1E 6BT, UK E-mail: [email protected] Yiorgos Chrysanthou is a lecturer in the Computer Science Department of University College London, UK. He received his BSc in Computer Science and Statistics (1990, 1st Class Honours) and his PhD in Computer Graphics (1996) from Queen Mary and Westfield College. During the period of 1996-98 he worked for as a research fellow on the COVEN (Collaborative Virtual ENvironments) ACTS project. His research interests include real-time rendering, virtual reality and computational geometry. 3 Claudio´ T. Silva AT&T Labs-Research Shannon Laboratory 180 Park Avenue – room D265 Florham Park, NJ 07932-0971 E-mail: [email protected] Cl´audio Silva is a Senior Member of Technical Staff in the Information Visualization Research Department at AT&T Research. Before joining AT&T, Cl´audio was a Research Staff Member at IBM T. J. Watson Research Center, where he worked on geometry compression, 3D scanning, visibility culling and polyhedral cell sorting for volume rendering. Claudio got his PhD in computer science at the State University of New York at Stony Brook in 1996. While a student, and later as an NSF post-doc, he worked at Sandia National Labs, where he developed large-scale scientific visualization algorithms and tools for handling massive datasets. His research interests include graphics, visualization, applied computational geometry, and high-performance computing. George Drettakis iMAGIS-GRAVIR/IMAG Inria Rhones-Alpes ZIRST - 655 avenue de l’Europe F-38330 Montbonnot Saint-Martin, France E-mail: [email protected] George received his Ptychion (B.Sc. equivalent) in 1988 from the Dept. of Computer Science in Crete, Greece. As an undergrad he worked at the ICS/FORTH on European Community research programs. Then completed Masters (in 1990) and Ph.D. (Jan 1994) at the Dept. of C.S. at the University of Toronto, Canada, under the supervision of Eugene Fiume . Dr. Drettakis also worked as a summer intern in 1990 at the Advanced Technology Group at Apple Computer in Cupertino Ca. in the US. Hi M.Sc. and Ph.D. were in Computer Graphics, and he worked in the Dynamic Graphics Project in Toronto. He was an ERCIM postdoctoral fellow in ’94-’95. The first part of his ERCIM postdoc (Jan. 94-Nov. 94) was at iMAGIS in Grenoble, France. The second part was in Barcelona, Spain at the UPC/LiSi graphics group (Dec. 94 to Mar. 24 1995). The last part of his ERCIM tour of Europe at VMSD-GMD in Germany (Mar. 24- Jul. 24 1995). He is now a member of the permanent researcher staff at iMAGIS- INRIA in Grenoble. 4 Contents Introduction to visibility Cohen-Or “A Survey of Visibility for Walkthrough Applications”, D. Cohen-Or, Y. Chrysanthou, and C. Silva, manuscript, 2000. Object-space visibility Silva “The Prioritized-Layered Projection Algorithm for Visible Set Estimation”, J. Klosowski and C. Silva, Submitted for publication, 2000. “Efficient Conservative Visibility Culling Using The Prioritized-Layered Projection Algorithm”, J. Klosowski and C. Silva, Submitted for publication, 2000. Image-space visibility Chrysanthou “Virtual occluders: An efficient intermediate pvs representation”, V. Koltun, Y. Chrysanthou, and D. Cohen-Or, Submitted for publication, 2000. The visibility complex Drettakis “A Multidisciplinary Survey of Visibility”, F. Durand, manuscript,2000. 5 9LVLELOLW\3UREOHPVIRU :DONWKURXJK$SSOLFDWLRQV 'DQLHO&RKHQ2U &RPSXWHU6FLHQFH'HSDUWPHQW 7HO$YLY8QLYHUVLW\ KWWSZZZPDWKWDXDFLOaGDQLHO 9LVLELOLW\3UREOHPVIRU:DONWKURXJK $SSOLFDWLRQV 'DQLHO&RKHQ2U7HO$YLY8QLYHUVLW\ <LRUJRV&KU\VDQWKRX8QLYHUVLW\&ROOHJHRI/RQGRQ &ODXGLR6LOYD$7 7/DEVUHVHDUFK *HRUJH'UHWWDNLVL0$*,6,15,$LQ*UHQREOH 9LUWXDO5HDOLW\$SSOLFDWLRQV 7KHXVHU´ZDONVµLQWHUDFWLYHO\LQDYLUWXDO SRO\JRQDOHQYLURQPHQW ([DPSOHVPRGHORIDFLW\PXVHXPPDOO DUFKLWHFWXUDOGHVLJQ 7KHJRDOWRUHQGHUDQXSGDWHG LPDJHIRUHDFKYLHZSRLQWDQGIRU HDFKYLHZGLUHFWLRQLQLQWHUDFWLYH IUDPHUDWH 7KH0RGHO &RPSRVHGRI' JHRPHWULFREMHFWV /RWVRIVLPSOHSDUWV /DUJHDQGFRPSOH[ KXQGUHGVWKRXVDQGV RUHYHQPLOOLRQVRI SRO\JRQV 7KH9LVLELOLW\3UREOHP 6HOHFWLQJWKH H[DFW" VHWRISRO\JRQVIURPWKH PRGHOZKLFKDUHYLVLEOH IURPDJLYHQYLHZSRLQW 7KH9LVLELOLW\3UREOHPLVLPSRUWDQW $YHUDJHQXPEHURI SRO\JRQVYLVLEOHIURPD YLHZSRLQWLVPXFKVÃPÃDÃOÃOÃHÃ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±,PDJH6WUXFWXUHJUDSK 7KHSODQQHUJUDSKGHILQHGE\WKHRXWOLQHV RIDQLPDJHFUHDWHGE\SURMHFWLRQRID SRO\KHGUDOREMHFWLQDFHUWDLQYLHZGLUHFWLRQ 7KH$VSHFW*UDSK &RQW $VSHFW 7ZRGLIIHUHQWYLHZGLUHFWLRQVRIDQREMHFW KDYHWKHVDPHDVSHFWLIIWKHFRUUHVSRQGLQJ ,PDJH6WUXFWXUHJUDSKVDUHLVRPRUSKLF 7KH$VSHFW*UDSK &RQW 963±9LVLELOLW\6SDFH3DUWLWLRQ 3DUWLWLRQLQJWKHYLHZVSDFHLQWRPD[LPDOFRQQHFWHG UHJLRQVLQZKLFKWKHYLHZSRLQWVKDYHWKHVDPHYLHZ RUDVSHFW 9LVXDO(YHQW $ERXQGDU\RID963UHJLRQFDOOHGD9(IRULWPDUNVD FKDQJHLQYLVLELOLW\ 7KH$VSHFW*UDSK &RQW $VSHFW*UDSK $YHUWH[IRUHDFKUHJLRQRIWKH963 $QHGJHFRQQHFWLQJDGMDFHQWUHJLRQV 5HJLRQVRIWKH963DUHQRWPD[LPDOEXWPD[LPDOFRQQHFWHGUHJLRQV $VSHFWJUDSK