This file lists the set of papers and tech reports that is written using IRIT.

Tech reports listed below may be ftp from ftp.technion.ac.il
[132.68.7.8], directory pub/supported/cs/Tech_Reports/199? as
cis????.ps.Z.

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		Line Illustrations $\in$ Computer Graphics

				Gershon Elber

The   revolution of the  computer graphics  field  during the last two
decades made it possible to create  high quality synthetic images that
even experts find it difficult to differentiate from real imagery.

In this  paper, we  explore  a partially  overlooked theme of computer
graphics that aims  at conveying simple  information using simple line
drawings and illustrations of polygonal as well as freeform objects.

* To appear in the Visual Computer. Also tech report CIS #9332,
  Computer Science Department, Technion, Januarry 1994
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     Proper Piecewise Linear Approximation of Freeform Surfaces.

			     Gershon Elber

We  present two models for  piecewise linear approximation of freeform
surfaces.  One model  exploits global  curvature bounds  and the other
employs an intermediate bilinear approximation. In both models, a norm
that  minimizes  the  maximal   deviation   of the  piecewise   linear
approximation from the freeform surface is used.

* Submitted for publication. Also tech report CIS #9413, Computer Science
  Department, Technion, October 1994
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       Symbolic and Numeric Computation in Curve Interrogation.

			     Gershon Elber

The control  of shape  of curves  is of  great importance  in computer
aided geometric design.   Determination  of planar curves'  convexity,
the  detection of  inflection  points,  coincident  regions, and  self
intersection points,  the enclosed  area of  a  closed curve,  and the
locations of extreme curvature  are important features of curves  that
can affect the design, in modeling environments.

In this paper, we investigate the ability to robustly answer the above
queries and related questions using an approach which exploits both
symbolic computation and numeric analysis.

* To appear in Computer Graphics {\it forum}. Also tech report CIS #9413,
  Computer Science Department, Technion, October 1994

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	    Adaptive Isocurves Based Rendering: the Hardware Way.

				Gershon Elber

In   a recent  work~\cite{Gershon-adap-iso-rend},  an   almost optimal
algorithm to provide a coverage based on the isoparametric curves of a
surface was  presented. This approach  was combined  successfully with
curve rendering techniques and used to  directly render surfaces using
isoparametric curves instead of polygons.

In this paper,  we describes an adaptation  of the rendering algorithm
that uses adaptive isoparametric curves  as the surface coverage, to a
generic hardware. We also discuss  the feasibility of implementing the
adaptive    isocurve extraction  algorithm   itself in   hardware. The
presented results make the surface  coverage using adaptive extraction
of isoparametric    curves a tool   for   competitive freeform surface
rendering in both software and hardware.

Several  results,  including  a  videotape  recording  of a  real time
display, are demonstrated.

* Presented in Computer Graphics International 1994 (CGI 94), Melbourne,
  Australia, June 1994.
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		Metamorphosis of Freeform Curves and Surfaces.

				Gershon Elber

Metamorphosis between two freeform \bspline{} curves is considered and
several approaches to control the process are discussed. Starting with
simple convex combination, we examine two  other approaches, one based
on multiresolution  decomposition of   freeform curves and   the other
based on edge cutting of the control polygon  of curves.  The later is
improved by introducing a correspondence test for simple metamorphosis
relation.   Finally, we consider  the  possibility of  extending these
algorithms to surfaces.

* To appear in Computer Graphics International 1995 (CGI 95), Leeds, UK,
  June 1995.
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		    Sketching as a Solid Modeling Tool

	       Lynn Eggli, Beat Bruderlin, and Gershon Elber.

This paper describes 'Quick-sketch', a 2d and 3d modeling tool for pen
based  computers. Users of this  system define a  model  by simple pen
strokes  drawn  directly  on  the  screen of  a  pen-based  PC. Lines,
circles, arcs, or B-spline curves are automatically distinguished, and
interpreted  from    these strokes.   The  system   also automatically
determines relations, such as right  angles, tangencies, symmetry, and
parallelism, from the sketch  input. These relationships are then used
to  clean  up  the drawing   by making  the  approximate relationships
exact. Constraints are  established to  maintain the relationships  in
further editing.  A  constraint maintenance system,  which is based on
gestural manipulation   and   soft constraints, is   employed  in this
system. Several techniques for sketch  based definitions of 3d objects
are  provided  as well,  including  extrusion,  surface of revolution,
ruled surfaces and sweep. Features can  be sketched on the surfaces of
3d objects, using the same 2d- and  3d techniques. This way objects of
medium complexity can be sketched in seconds. The system can be viewed
as a front-end to more  sophisticated modeling, rendering or animation
environments,  serving as a hand    sketching tool in the  preliminary
design phase.

* To appear in Solid Modeling 95, Salt Lake City, Utah, May 1995.
