random.C

/*
 * This file is part of the "Archon" framework.
 * (http://files3d.sourceforge.net)
 *
 * Copyright © 2002 by Kristian Spangsege and Brian Kristiansen.
 *
 * Permission to use, copy, modify, and distribute this software and
 * its documentation under the terms of the GNU General Public License is
 * hereby granted. No representations are made about the suitability of
 * this software for any purpose. It is provided "as is" without express
 * or implied warranty. See the GNU General Public License
 * (http://www.gnu.org/copyleft/gpl.html) for more details.
 *
 * The characters in this file are ISO8859-1 encoded.
 *
 * The documentation in this file is in "Doxygen" style
 * (http://www.doxygen.org).
 */

#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#include <math.h>

#include <archon/util/random.H>

static bool initialized;

static void init()
{

  time_t t;

  /* Initialize random number generator */
  time(&t);
  srand(static_cast<unsigned>(t) + static_cast<unsigned>(getpid()));

  initialized = true;
}

namespace Archon
{
  namespace Utilities
  {
    int drawInt(int bound)
    {
      if(!initialized) init();
      return static_cast<int>(static_cast<double>(bound)*rand()/(RAND_MAX+1.0));
    }

    double drawFloat()
    {
      if(!initialized) init();
      return rand()/static_cast<double>(RAND_MAX);
    }

    double drawFloatOpen()
    {
      if(!initialized) init();
      return rand()/(RAND_MAX+1.0);
    }

    Math::Vector3 drawUnitVector3()
    {
      Math::Vector3 w;
      w[2] = drawFloat() * 2 - 1;
      double r = sqrt(1 - w[2] * w[2]);
      double a = drawFloatOpen() * 2 * M_PI;
      w[0] = r * cos(a);
      w[1] = r * sin(a);
      return w;
    }
  }
}

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