<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<html>
<title>GLE Tubing and Extrusion Fact Sheet</title>
<meta name="description" content="The GLE Tubing and Extrusion Library
is a graphics programming interface (API) for drawing
tubing, extrusions and sweeps using the OpenGL API.">
<meta name="keywords" content="GLE, tubing, extrusion, graphics, OpenGL,
lathe, sweep, torus, polycylinder, polycone, contour, parallel
translation, helix, texture mapping">
<body>
<h1>GLE Tubing and Extrusion Fact Sheet</h1>
<a href="http://www.opengl.org/">
<img align=right src="ogla_sm.gif" alt="OpenGL Logo">
</a>
<a href="http://sourceforge.net">
<img src="http://sourceforge.net/sflogo.php?group_id=5539"
align=right width="88" height="31" border="0" alt="SourceForge Logo">
</a>
<br>
<h2>The Hard Facts</h2>
The GLE Tubing and Extrusion Library is a graphics application
programming interface (API). The library consists of a number
of "C" language subroutines for drawing tubing and extrusions.
It is a very fast implementation of these shapes, outperforming
all other implementations, most by orders of magnitude.
The library is distributed in source code form, in a package
that includes documentation, a VRML proposal, Makefiles, and
full source code and header files. It uses the OpenGL (TM)
programming API to perform the actual drawing of the tubing and
extrusions.
<p>
GLE is designed for and maintained on the
<a href="http://www.linas.org/linux/graphics-ad.html">Linux</a>
operating system, and is known to run on other Unix operating systems
such as
<a href="http://www.rs6000.ibm.com">AIX</a>,
<a href="http://www.sgi.com">IRIX</a>, Ultrix and HPUX with
<a href="http://www.opengl.org">OpenGL</a> or
<a href="http://www.mesa3d.org">Mesa</a>.
GLE is also known to run on
<a href="http://www.software.ibm.com/os/warp/index.html">
IBM OS/2 Warp</a>, Apple Macintosh OS9, and Microsoft Windows NT
and has been used to develop screen-savers for some of these popular
PC operating systems.
<p>
<b>News:</b> Dave Richards has created a set of MSWindows-specific C++
classes that are derived from gle. See the
<a href="http://www.quiknet.com/~moriarty/">GLE32</a> site.
(<a href="http://www.linas.org/mirrors/www.quiknet.com/~moriarty/">mirror</a>)
<p>
<b>News:</b> There is now a mailing list to discuss gle:
<tt>gle-discuss@lists.sourceforge.net</tt>.
Subscribe <a href="http://lists.sourceforge.net/mailman/listinfo/gle-discuss">
by web</a> or
<a href="http://www.geocrawler.com/redir-sf.php3?list=gle-discuss">
view the archives</a>.
<p>
<b>News:</b> Version 3.0 is out, sporting an improved/simplified
build system, which should make compiling this package a lot less
confusing. Project has been moved to
<a href="http://sourceforge.net/project/?group_id=5539">SourceForge</a>,
which means you can get live CVS, and should make it easier for
folks to submit patches & participate in this project.
<p>
<b>News:</b> <a href="http://www.symbolstone.org/technology/java">
ShapeShifter</a> is a re-write of the GLE library in Java.
Available freely, under the 'Artistic License'.
<p>
<b>News:</b> OpenGL internals programmers & hardware developers,
<a href="http://www.linas.org/linux/graphics-ad.html">
please read this.</a>
<p>
<b>News:</b> Python bindings are shipped with this release.
They were generated with a non-standard version of SWIG.
There is also another (different) set of bindings for GLE that
come standard with OpenGL at the
<a href="http://pyopengl.sourceforge.net/">PyOpenGL site</a>.
At this point, neither set should be considered to be more
'standard' than the other.
<p>
<img src="basic.gif">
<img src="texscr.gif">
<img src="twist3.gif">
<p>
<h2>A Gentle Introduction</h2>
The libgle.a library contains a collection of routines for drawing
sweeps and extrusions. A "sweep" or "extrusion" is a 2D contour
(polyline) that is swept or extruded along a 3D path (polyline).
For example, sweeping a circle along a straight line will generate
a cylinder. Sweeping a circle along a circular path will generate
a doughnut (torus).
<p>
The library also includes a set of utility routines for drawing some of
the more common extruded shapes: a polycylinder, a polycone, a
generalized torus (circle swept along a helical path), a "helix"
(arbitrary contour swept along a helical path) and a "lathe" (arbitrary
contour swept along a helical path, with torsion used to keep the
contour aligned).
<p>
<! <img src="helix.gif">
<img src="helix2.gif">
<img src="helixtex.gif">
<p>
The most general extrusion supported by this library allows an arbitrary
2D contour to be swept around an arbitrary 3D path. A set of normal
vectors can be specified to go along with the contour; the normal vectors
determine the appearance of the contour when lighting is turned on.
A set of colors and affine matrices can be specified to go along with
the 3D path. The colors are used to color along the path. The affine
matrices are used to operate on the contour as it is swept along. If no
affine matrices are specified, the contour is extruded using the
mathematical concept of "parallel translation" or "Gaussian
translation". That is, the contour is moved (and drawn) along the
extrusion path in a "straight" manner. If there are affine matrices,
they are applied to the contour at each extrusion segment before the
segment is drawn.
<p>
<img src="helix4.gif"> <img src="shear.gif">
<p>
The affine matrices allow work in a quasi-non-Euclidean space.
They essentially allow the contour to be distorted as it is swept
along. The allow the contour to be rotated, translated and
rescaled as it is drawn. For example, a rescaling will turn a
polycylinder into a poly-cone, since the circle that is being
extruded is scaled to a different size at each extrusion vertex.
A rotation allows the contour to be spun around while it is being
extruded, thus for instance allowing drill-bit type shapes to be
drawn. A translation allows the appearance of shearing in
real space; that is, taking a contour and displacing it,
without otherwise bending it. Note that the affines are
2x3 matrices, not 3x4 matrices, since they apply to the 2D
contour as it is being extruded.
<p>
<h2>Table of Contents</h2>
<ul>
<li><a href="tube.html">Tubing & Extrusions Subroutine Documentation</a>
<li><a href="join.html">JoinStyle Subroutine Documentation</a>
<li><a href="texture.html">Texture Generation</a>
<li><a href="build.html">Compiling the Library</a>
<li><a href="pipeline.html">Design & Implementation Internals, the Pipeline</a>
<li><a href="vrml.html">A VRML Extension Proposal</a>
<li><a href="http://www.linas.org/gle/index.html">The GLE Web Site</a>
<li><a href="http://sourceforge.net/projects/gle/">GLE on
SourceForge</a> (live CVS)
<li><a href="http://www.linas.org/gle/pub/gle-3.0.lsm">The GLE LSM entry</a>
<li><a href="http://www.linas.org/gle/pub/">Source Code
Distribution (Primary -- linas.org)</a>
<li><a href="http://metalab.unc.edu/pub/Linux/libs/X/gle-3.0.1.tar.gz">Source
Code Distribution (Secondary -- Metalab)</a>
<li><a href="ftp://tsx-11.mit.edu/pub/linux/sources/libs/gle.2.2.7.tar.gz">Source Code Distribution (Secondary -- TSX-11)</a>
</ul>
<h2> Version Summary </h2>
Version 1.0 -- Originally developed by Linas Vepstas for IBM GL 3.2
and SGI IrisGL in 1991<br>
Version 2.0 -- Port to OpenGL, March, July, October 1993 <br>
Version 2.1 -- Port demos to GLUT Library, assorted lint/compile time
cleanup, April 1995<br>
Version 2.1.1 -- Additional demos, October 1995<br>
Version 2.2.0 -- Fully HTML'ized documentation, Christmas 1995 <br>
Version 2.2.1 -- Additional demos <br>
Version 2.2.2 -- Extensive screen shots added to documentation, January 1996 <br>
Version 2.2.3 -- VRML proposal, February 1996 <br>
Version 2.2.4 -- metalab (prev. sunsite), tsx-11 post, March 1996 <br>
Version 2.2.5 -- Documentation cleanup, July 1996 <br>
Version 2.2.6 -- Documentation cleanup, April 1997 <br>
Version 2.2.7 -- Minor bug fixes, December 1997 <br>
Version 2.3 -- Bug fixes for drawing of end caps for MesaGL,
man pages from Mark Kilgard, December 1997 <br>
Version 3.0.0 -- Consolidation, simplification of build structure;
major version number changed because header files
consolidated and renamed.
Use automake/autoconf to build.
Move CVStree to sourceforge. June 2000<br>
Version 3.0.1 -- Misc bug fixes, configure.in fix<br>
Version 3.0.2 -- C++ wrapper fixes<br>
Version 3.0.3 -- look for libXmu in configure<br>
Version 3.0.4 -- python bindings, minor bug fix<br>
Version 3.0.5 -- Visual C project files;
create pipeline documentation;
fix makefile to install docs, examples.<br>
Version 3.0.6 -- disable fprintf(stderr) on Win32 systems.
use newer automake/autoconf configure.
Add GPL as an alternate license choice.
November 2001.<br>
<br>
Version 3.0.7 -- configure.in libXi fix for detecting libglut.<br>
<p>
<h2> Credits </h2>
Written and maintained by Linas Vepstas
<a href="mailto:linas@linas.org">linas@linas.org</a>. <br>
Many thanks Mark Kilgard for converting the web pages to real Unix
man pages.
<br>
Visit my <a href="http://www.linas.org/linux/">Enterprise Linux</a> web
site for more info about Linux in a commercial, business setting.
<p>
</body>
</html>
