Israel SIGGRAPH meeting on January 26

Israel SIGGRAPH meeting on January 26, 1996

Chair: Daniel Cohen-Or
Tel-Aviv University

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 abstract #6 on the exposed columns.

Time	Speaker	Title	Abstract
8:30		REFRESHMENTS
9:00	Hanan Samet University of Maryland	Ranking in Graphical Databases	The speaker introduced and analyzed an algorithm for ranking spatial objects according to increasing distance from a query object. The algorithm makes use of a hierarchical spatial data structure. The intended application area is a database environment, where the spatial data structure serves as an index. The algorithm is incremental in the sense that objects are reported one by one, so that a query processor can use the algorithm in a pipelined fashion for complex queries involving proximity. It is well suited for k nearest neighbor queries, and has the property that k need not be fixed in advance. The algorithm has been used as the basis of a browser for graphical objects in a relational database.
9:30	Hod Lipson Technion - Israel Institute of Technology	Reconstruction of a 3D Object from a Single Freehand Sketch	Freehand sketching appears to be a natural communication language: it provides the means to convey qualitative information rapidly, without impeding user creativity or disrupting the flow of ideas. The speaker proposes and implements a new sketch-based user interface for 3D conceptual design. There are several difficulties in implementing this kind of interface. The primary difficulty is that the reconstruction is mathematically indeterminate because the 2D sketch lacks 3D depth information. Inaccuracies inherent in the freehand sketch intensify the difficulty. The speaker presented some of the algorithms used to overcome these difficulties.
10:00	Dan Gordon University of Haifa	The End of the Z-Buffer?	The Z-buffer is the simplest method for hidden surface removal, but it requires a large memory. By using the ``critical points'' polygon scan conversion technique, the rendering of arbitrary polygons can be dovetailed so that only a single scanline Z-buffer (called an S-buffer) is required. The final image is produced in scanline order. The speaker discussed several applications of this method.
10:30		COFFEE BREAK
11:15	Shay Dekel ScanVec Ltd.	Rounding and Blending a Solid	Most solid modelers today have rounding and blending functionalities. Typically, the user can define a constant radius or a variable radius function on edges of the solid that he or she wishes to round; the application automatically replaces these edges with round surfaces, creates blend surfaces in vertices of the solid where the round surfaces meet, and extends the rounding operations to leave the solid in a legal, ``closed'' state. The speaker presented the framework of such functionality, and concentrated on two main algorithms: producing improved (variable) round NURBS surfaces using the rational B-spline representation of arcs; creating a blend surface using the finite element method.
11:45	Jacky Romano Silicon Graphics (Israel) Ltd.	Indigo2 Impact Graphics - Texture Mapping on the Desktop	The speaker concentrated on the architecture of the Impact Graphics boards. He discussed their performance characteristics, and showed techniques of using the texture mapping functionality in interesting ways, such as reflections, volume rendering, Phong shading and projected textures.
12:15	Shai Avidan Hebrew University	Novel-View Synthesis from a Collection of Perspective Views for the Purpose of Image-Based Rendering	The speaker presented a new method for synthesizing novel views of a 3D scene from three reference images and their trilinear tensor. No use of a 3D model of the scene is made, nor any use of camera geometry (relative locations of the cameras) of the three views is required - only the computation of the trilinear tensor. The novel views are modeled by specifying rotation and translation of the virtual camera starting from one of the reference views, which is an ideal ``driving'' mode for generating a synthetic movie. The synthesis process is governed by a simple equation (relating the model tensor and the new tensor) in which the user-specified virtual camera is plugged in, followed by a warping step; hence, the only time consuming component in this process is image warping. The virtual camera can be anywhere in 3D, and the quality of the synthesized images is limited only by the quality of the (dense) correspondence between two of the reference images and the amount of self-occlusions in the scene.