src/Accum.cpp

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/*
This file is part of Teapot Colony Wars.

Teapot Colony Wars is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 2 of the License, or
(at your option) any later version.

Teapot Colony Wars is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Teapot Colony Wars.  If not, see <http://www.gnu.org/licenses/>.
*/

/*
 * Copyright (c) 1993-1997, 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 * Unpublished-- rights reserved under the copyright laws of the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(R) is a registered trademark of Silicon Graphics, Inc.
 */

#include "Accum.h"

#include <cmath>

#include "Constants.h"

void accFrustum(GLdouble left, GLdouble right, GLdouble bottom,
                GLdouble top, GLdouble near, GLdouble far, GLdouble pixdx,
                GLdouble pixdy, GLdouble eyedx, GLdouble eyedy, GLdouble focus)
{
  // make a frustum for use with the accumulation buffer
  GLdouble xwsize, ywsize;
  GLdouble dx, dy;
  GLint viewport[4];

  glGetIntegerv(GL_VIEWPORT, viewport);
  xwsize = right - left;
  ywsize = top - bottom;
  dx = -(pixdx * xwsize / (GLdouble)viewport[2] + eyedx * near / focus);
  dy = -(pixdx * ywsize / (GLdouble)viewport[3] + eyedy * near / focus);

  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();

  glFrustum(left + dx, right + dx, bottom + dy, top + dy, near, far);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glTranslatef(-eyedx, -eyedy, 0.0);
}

void accPerspective(GLdouble fovy, GLdouble aspect,
                    GLdouble near, GLdouble far, GLdouble pixdx, GLdouble pixdy,
                    GLdouble eyedx, GLdouble eyedy, GLdouble focus)
{
  GLdouble fov2, left, right, bottom, top;
  fov2 = ((fovy * PI) / 180.0) / 2.0;

  top = near / (cos(fov2) / sin(fov2));
  bottom = -top;
  right = top * aspect;
  left = -right;

  accFrustum(left, right, bottom, top, near, far,
             pixdx, pixdy, eyedx, eyedy, focus);
}

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