Israel SIGGRAPH meeting on June 1

Israel SIGGRAPH meeting on Nov 15, 2002

Ivcher Auditorium,
The Interdisciplinary Center, Herzelia

(directions to get to IDC can be found here)

Chair: Alla Sheffer
Center for Graphics and Geometric Computing CGGC
Technion

The following program is also available in fdf format. The PostScript file is to be printed double-sided on A4 paper, and folded into three columns with INVITATION and the digit "3" on the exposed columns.

Time	Speaker	Title	Abstract
8:30	Refreshments
9:00	Shmulik Moradoff, Hebrew University, Jerusalem	Constrained Synthesis of Textural Motion for Animation	Obtaining high quality, realistic motions of articulated characters is both time consuming and expensive, necessitating the development of easy-to-use and effective tools for motion editing and reuse. We propose a new simple technique for generating constrained variations of different lengths from an existing captured or otherwise animated motion. Our technique is applicable to textural motions, such as walking or dancing, where the motion sequence can be decomposed into shorter motion segments without an obvious temporal ordering among them. Inspired by previous work on texture synthesis and video textures, our method essentially produces a re-ordering of these shorter segments. Discontinuities are eliminated by carefully choosing the transition points and applying local adaptive smoothing in their vicinity, if necessary. The user is able to control the synthesis process by specifying a small number of simple constraints. Joint work with Dani Lischinski
9:30	Boris Lipschitz, Technion	Verification of Scanned Engineering Parts with CAD Models based on Discrete Curvature Analysis	The manufacturing industry constantly needs to verify machined objects with the original CAD models. Given a prototype design of a solid model, the manufacturing engineer should be able to determine whether the part was manufactured well, that is, whether it fits the CAD model exactly. But in many cases, spatial fitting of corresponding points is not sufficient. The current work attempts to check the possibility of comparing the curvatures of corresponding objects. Curvature is an invariant surface property that is not affected by the choice of the coordinate system, the position of the viewer, and the particular parameterization of the surface. In recent years advances in 3D scanning technology have enabled highly accurate results with relatively low noise. Nevertheless, derivative computation is unstable for real data, and the estimated curvature is thus very noise-sensitive. The proposed method is applied on a given mesh, which is constructed from sampled points. The curvature for triangular meshes is not defined. The faces are flat and thus have zero curvature, and only continuity at the vertices as edges. However, triangle faces are piecewise linear approximations of the sampled object. So, the curvature of unknown surfaces can be estimated by extracting information from the triangular mesh. Most algorithms can approximate the curvature of synthetic meshes quite accurately, but they fail with real noisy data. In the current research algorithms that deal with noisy data were implemented. Some of them were extended in order to improve the results. During the lecture presentation, several curvature estimation algorithms for triangular meshes that were implemented, analyzed and extended will be described. These algorithms for noisy data will be presented. Joint work with Anath Fischer
10:0	Iddo Drori, Tel-Aviv University	Example-Based Image Completion	We present a new method for completing the hidden parts of an image based on the visible parts, including shape, color and texture. Our goal is reconstructing the hidden parts, to get a small error with high confidence, and to synthesize a complete, visually plausible, and coherent image. We introduce an example-based completion method which utilizes the visible parts of an image as a training set to infer the hidden parts. Our approach is to first approximate the hidden parts using a fast multi-grid method, and then complete the details according to the most similar and frequent examples by adaptive tessellation. We demonstrate our method by seamless completion of various paintings and images. Joint work with Daniel Cohen-Or and Hezy Yeshurun
10:30	Coffee Break
11:00	Alexander Bogomjakov, CGGC, Technion	Efficient Compression and Rendering of Multi-Resolution Meshes	We present a method to code the multiresolution structure of a 3D triangle mesh in a manner that allows progressive decoding and efficient rendering at a client machine. The code is based on a special ordering of the mesh vertices which has good locality and continuity properties, inducing a natural multiresolution structure. This ordering also incorporates information allowing efficient rendering of the mesh at all resolutions using the contemporary vertex buffer mechanism. The performance of our code is shown to be competitive with existing progressive mesh compression methods, while achieving superior rendering speed. Joint work with Zachi Karni and Craig Gotsman
11:30	Nira Dyn, Tel-Aviv University	Spline Subdivision Schemes for Compact Sets	Motivated by the problem of the reconstruction of 3D objects from their 2D cross sections, we consider the use of spline subdivision schemes operating on data consisting of compact 2D sets. A spline subdivision scheme generates from such data a sequence of piecewise-linear functions, with compact 2D sets as images, which converges to a limit function with compact 2D sets as images (set-valued function). This set-valued function describes a 3D object. For the case of 2D convex cross-sections, we replace addition of scalars in the spline subdivision schemes, by Minkowski sums of sets. Then the spline subdivision schemes generate 3D objects with convex cross-sections. Such a limit 3D object has a simple representation in terms of the given cross-sections, and approximates the 3D object from which the given cross-sections are sampled. For the case of non-convex initial cross-sections we show that the limit of any spline subdivision scheme, using the Minkowski sums, has convex cross-sections, and is too large to be a good approximation to the 3D object with the given cross-sections. For general cross-sections, we use the representation of spline subdivision schemes in terms of repeated binary averages, and replace the usual average of two scalars by a binary operation between two compact sets, termed the "metric average". The resulting schemes are shown to converge in the Hausdorff metric, generating 3D objects which approximate the sampled objects. Joint work with E. Farkhi
12:00	Yochai Shefi-Simchon, Silicon Graphics Israel	OpenGL Vizserver	OpenGL Vizserver is a transparent software solution which allows a desktop user to view and interact with OpenGL applications running on high-end graphics machines, as well as collaborating with other users. The talk will cover the motivation behind OpenGL Vizserver and the VAN (Visual Area Network) concept, the problems it solves, its architecture and way of operation and its future development plans.