Last Modified
  2013-10-03 00:37:20 +0000
Requires

## Description

# Based on trackball.rb in the Logo demo code: # ruby-gnome2.sourceforge.jp/hiki.cgi?Logo # # Original code license is: #

    trackball.rb
      Implementation of a virtual trackball and vector.

      Copyright (c) 2004 Masao Mutoh

      You can redistribute it and/or modify it under the terms of
      the original code license below.

      Original code license is:

/*

    * (c) Copyright 1993, 1994, Silicon Graphics, Inc.
    * ALL RIGHTS RESERVED
    * Permission to use, copy, modify, and distribute this software for
    * any purpose and without fee is hereby granted, provided that the above
    * copyright notice appear in all copies and that both the copyright notice
    * and this permission notice appear in supporting documentation, and that
    * the name of Silicon Graphics, Inc. not be used in advertising
    * or publicity pertaining to distribution of the software without specific,
    * written prior permission.
    *
    * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS"
    * AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
    * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR
    * FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT SHALL SILICON
    * GRAPHICS, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
    * SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY
    * KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION,
    * LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
    * THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC.  HAS BEEN
    * ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
    * ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
    * POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE.
    *
    * US Government Users Restricted Rights
    * Use, duplication, or disclosure by the Government is subject to
    * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
    * (c)(1)(ii) of the Rights in Technical Data and Computer Software
    * clause at DFARS 252.227-7013 and/or in similar or successor
    * clauses in the FAR or the DOD or NASA FAR Supplement.
    * Unpublished-- rights reserved under the copyright laws of the
    * United States.  Contractor/manufacturer is Silicon Graphics,
    * Inc., 2011 N.  Shoreline Blvd., Mountain View, CA 94039-7311.
    *
    * OpenGL(TM) is a trademark of Silicon Graphics, Inc.
    */

/*

    * Trackball code:
    *
    * Implementation of a virtual trackball.
    * Implemented by Gavin Bell, lots of ideas from Thant Tessman and
    *   the August '88 issue of Siggraph's "Computer Graphics," pp. 121-129.
    *
    * Vector manip code:
    *
    * Original code from:
    * David M. Ciemiewicz, Mark Grossman, Henry Moreton, and Paul Haeberli
    *
    * Much mucking with by:
    * Gavin Bell
    */