*******************************************************************
             SIPP  --  3d rendering package

             Copyright  Equivalent Software HB   1992

             Authors:   Jonas Yngvesson   jonas-y@isy.liu.se
                        Inge Wallin       ingwa@isy.liu.se
                 _
             Linkoping Institute of Technology
             Sweden

             Modifications by Mark Diekhans (markd@grizzly.com)
*******************************************************************

This directory contains a modified version of the SIPP 3.0 libsipp sources that
support features of Tcl-SIPP.

The entire libsipp source is included in this, directory.  If you wish to get
the entire SIPP 3.0 distribution, including documentation, it is available
from:

        wuarchive.wustl.edu:/graphics/graphics/packages/sipp/sipp-3.0.tar.Z
     or
        isy.liu.se:/pub/sipp/sipp-3.0.tar.Z (note: this site is in Sweden)

  The following changes have been made, (along with the files changed).
Context diffs are available in this directory (*.cdiff).  These changes
have been submitted to the owners of SIPP for consideration for inclusion
in future versions of SIPP.

o Optionally rendering from the bottom of the picture to the top to allow
  correct output to RLE file. (rendering.c)

o Added an optional callback function that is called periodically during
  rendering to handle X events in Tk.  A function has been added to support
  aborting a rendering in progress. (rendering.c)

o Fixed minor bugs and protability problems. (lightsource.c xalloca.h)

o Change method of storing subobjects and surface to prevent memory loss and
  potential memory corruption. (objects.c, bezier.c, cone.c, ellipsoid.c,
  prism.c, rendering.c sipp.h torus.c)

o Added the ability to have an optional header on surface descriptions passed
  to surfaces.  The header contains a reference count and pointer to a 
  function to free the surface descriptor when no longer referenced.
  (sipp.h, objects.c).
