Israel SIGGRAPH meeting on May 5

Israel SIGGRAPH meeting on May 5, 2000

MELAMED Hall (06), School of Exact Sciences
Tel-Aviv University

Chair: Craig Gotsman
Dept. of Computer Science
Technion

The following program is also available in PostScript format. The PostScript file is to be printed double-sided on A4 paper, and folded into three columns with INVITATION and the digit "5" on the exposed columns. The invitation also serves as an entrance permit for your car at gate 1 of the Tel-Aviv University campus.

Time Speaker Title Abstract

8:30 REFRESHMENTS

9:00 Gershon Elber

Dept. of Computer Science

Technion Revisiting Linear Constraints Positional, tangential, and orthogonality constraints are all linear and can be easily incorporated into freeform curve and surface editing environment, as is well known. In this work, we show that the symmetry as well as the area constraint could also be reformulated as linear constraints and similarly incorporated into the editing environment.
Incorporated into a multiresolution editing framework, we will demonstrate the use of these linear constraints for curves and possible discuss the feasibility of extending these results to freeform surfaces.

9:30 Seth Teller
MIT Computer Graphics Group
Automated Model Capture
in Extended Urban Environments Environment capture, or ``geometric modeling'' -- acquiring a representation of an object in a form useful for computer simulation -- is an essential first step in visualization, simulation, and computer-aided design. Researchers have developed techniques for extracting geometric and appearance information directly from photographs. Existing model capture tools are manually intensive, relying heavily on a ``human in the loop'' for a variety of tasks. This imposes fundamental limitations on scale, complexity, and capture rates.
This paper describes the development of fully automated computer vision techniques for capturing rich, textured 3D CAD models of urban areas directly from near-ground photographs. We'll show a novel sensor which acquires high-resolution geo-referenced images, and accompanying algorithms which extract textured geometric models of the environment observed by the sensor. The tradeoff is that, in return for automation, this task requires specialized sensor instrumentation, large numbers (typically thousands) of image observations, and significant computational resources.

Eliminating the human in the loop is a significant challenge from both engineering and research standpoints, and the effort has led to some powerful new techniques. In contrast to the prevailing view that human intervention always improves quality, we give examples of situations in which our automated system outperforms a human operator. We describe the current status of the project and show some preliminary results.

10:30 COFFEE BREAK

11:00 Leo Joskowicz
School of Computer Science and Engineering

The Hebrew University
Practical Translational Assembly Planning:
Framework and Applications We present a framework for general translational assembly planning based on linear constraints. We show that m-handed assembly planning can be reduced to testing for unboundedness, and present the first polynomial-time algorithm for $m$-handed assembly of polygonal part assemblies with no initially separated pairs of parts. We describe a new algorithm that performs a linear unboundedness test by solving a single homogeneous system of equations followed by a single linear feasibility test. We show that testing for unboundedness is computationally at least as hard as these two subproblems. The new algorithm is the fastest known algorithm and is practical. We demonstrate the practicality of our algorithms with experimental results of our implementations on planar and spatial examples, including puzzles and furniture.
Joint work with Fabian Schwarzer and Achim Schweikard
Institut fur Informatik, Technische Universitat Munchen. GERMANY

11:30 Zachi Karni

Dept. of Computer Science

Technion
Spectral Compression of Mesh Geometry We show how spectral JPEG-type methods may be applied to 3D mesh data to obtain compact representations. These methods are based on projecting the mesh geometry on an orthogonal basis derived from the mesh topology. To reduce complexity, the mesh is partitioned to a large number of balanced submeshes with minimal edge-interaction, which are then compressed separately.
Our compression scheme may be used for static and progressive transmission of 3D content, and are shown to be vastly superior to existing methods using spatial techniques, if slight loss can be tolerated.

Joint work with Craig Gotsman

12:00 Jihad El-Sana
Department of Computer Science

Ben-Gurion University of The Negev
Multi-User View-Dependent Rendering In this talk we are presenting a novel architecture which allows rendering of large-shared dataset at interactive rates on an inexpensive workstation. The idea is based on view-dependent rendering on a client-server network. The server stores the large dataset and manages the selection of the various levels of detail, while the inexpensive clients receive a stream of update operations that form the appropriate level of detail in an incremental fashion. These update operations are based on the changes in the clients' view-parameters. Our approach dramatically reduces the amount of memory needed by each client and the entire computing system, since the dataset is stored only once, on the server. In addition, it decreases the load on the network, as results of the incremental update contributed by view-dependent rendering.

Time	Speaker	Title	Abstract
8:30		REFRESHMENTS
9:00	Gershon Elber Dept. of Computer Science Technion	Revisiting Linear Constraints	Positional, tangential, and orthogonality constraints are all linear and can be easily incorporated into freeform curve and surface editing environment, as is well known. In this work, we show that the symmetry as well as the area constraint could also be reformulated as linear constraints and similarly incorporated into the editing environment. Incorporated into a multiresolution editing framework, we will demonstrate the use of these linear constraints for curves and possible discuss the feasibility of extending these results to freeform surfaces.
9:30	Seth Teller MIT Computer Graphics Group	Automated Model Capture in Extended Urban Environments	Environment capture, or ``geometric modeling'' -- acquiring a representation of an object in a form useful for computer simulation -- is an essential first step in visualization, simulation, and computer-aided design. Researchers have developed techniques for extracting geometric and appearance information directly from photographs. Existing model capture tools are manually intensive, relying heavily on a ``human in the loop'' for a variety of tasks. This imposes fundamental limitations on scale, complexity, and capture rates. This paper describes the development of fully automated computer vision techniques for capturing rich, textured 3D CAD models of urban areas directly from near-ground photographs. We'll show a novel sensor which acquires high-resolution geo-referenced images, and accompanying algorithms which extract textured geometric models of the environment observed by the sensor. The tradeoff is that, in return for automation, this task requires specialized sensor instrumentation, large numbers (typically thousands) of image observations, and significant computational resources. Eliminating the human in the loop is a significant challenge from both engineering and research standpoints, and the effort has led to some powerful new techniques. In contrast to the prevailing view that human intervention always improves quality, we give examples of situations in which our automated system outperforms a human operator. We describe the current status of the project and show some preliminary results.
10:30		COFFEE BREAK
11:00	Leo Joskowicz School of Computer Science and Engineering The Hebrew University	Practical Translational Assembly Planning: Framework and Applications	We present a framework for general translational assembly planning based on linear constraints. We show that m-handed assembly planning can be reduced to testing for unboundedness, and present the first polynomial-time algorithm for $m$-handed assembly of polygonal part assemblies with no initially separated pairs of parts. We describe a new algorithm that performs a linear unboundedness test by solving a single homogeneous system of equations followed by a single linear feasibility test. We show that testing for unboundedness is computationally at least as hard as these two subproblems. The new algorithm is the fastest known algorithm and is practical. We demonstrate the practicality of our algorithms with experimental results of our implementations on planar and spatial examples, including puzzles and furniture. Joint work with Fabian Schwarzer and Achim Schweikard Institut fur Informatik, Technische Universitat Munchen. GERMANY
11:30	Zachi Karni Dept. of Computer Science Technion	Spectral Compression of Mesh Geometry	We show how spectral JPEG-type methods may be applied to 3D mesh data to obtain compact representations. These methods are based on projecting the mesh geometry on an orthogonal basis derived from the mesh topology. To reduce complexity, the mesh is partitioned to a large number of balanced submeshes with minimal edge-interaction, which are then compressed separately. Our compression scheme may be used for static and progressive transmission of 3D content, and are shown to be vastly superior to existing methods using spatial techniques, if slight loss can be tolerated. Joint work with Craig Gotsman
12:00	Jihad El-Sana Department of Computer Science Ben-Gurion University of The Negev	Multi-User View-Dependent Rendering	In this talk we are presenting a novel architecture which allows rendering of large-shared dataset at interactive rates on an inexpensive workstation. The idea is based on view-dependent rendering on a client-server network. The server stores the large dataset and manages the selection of the various levels of detail, while the inexpensive clients receive a stream of update operations that form the appropriate level of detail in an incremental fashion. These update operations are based on the changes in the clients' view-parameters. Our approach dramatically reduces the amount of memory needed by each client and the entire computing system, since the dataset is stored only once, on the server. In addition, it decreases the load on the network, as results of the incremental update contributed by view-dependent rendering.