# include <stdio.h>
# include <stdlib.h>

# include <GL/glut.h>
# include <GL/freeglut.h>

int main ( int argc, char *argv[] );
void display ( );
void myinit ( );

typedef GLfloat point2[2];

/******************************************************************************/

int main ( int argc, char *argv[] )

/******************************************************************************/
/*
  Purpose:

    fern_opengl() draws the Barnsley fractal fern by plotting points.

  Discussion:

    The main program calls GLUT functions to set up the windows,
    name the required callbacks and callback functions, in particular
    the DISPLAY callback.

  Licensing:

    This code is distributed under the MIT license.

  Modified:

    06 March 2017

  Reference:

    Edward Angel,
    Interactive Computer Graphics:
    A Top-Down Approach with OpenGL,
    Second Edition,
    Addison Wesley, 2000.

    Michael Barnsley,
    Fractals Everywhere,
    Academic Press, 1988,
    ISBN: 0120790696,
    LC: QA614.86.B37.

    Cleve Moler,
    Experiments with MATLAB,
    ebook: http:www.mathworks.com/moler/exm/index.html
*/
{
  printf ( "\n" );
  printf ( "fern_opengl():\n" );
  printf ( "  C version\n" );
  printf ( "  This OpenGL program displays the Barnsley fractal fern.\n" );

  glutInit ( &argc, argv );
  glutInitDisplayMode ( GLUT_SINGLE | GLUT_RGB );
  glutInitWindowSize ( 400, 600 );
  glutInitWindowPosition ( 0, 0 );
  glutCreateWindow ( "Barnsley Fractal Fern" );
  glutDisplayFunc ( display );

  myinit ( );

  glutMainLoop ( );
/*
  Terminate.
*/
  printf ( "\n" );
  printf ( "FERN:\n" );
  printf ( "  Normal end of execution.\n" );

  return 0;
}
/******************************************************************************/

void display ( )

/******************************************************************************/
/*
  Purpose:

    DISPLAY generates the graphics output.

  Licensing:

    This code is distributed under the MIT license.

  Modified:

    09 May 2011

  Reference:

    Edward Angel,
    Interactive Computer Graphics:
    A Top-Down Approach with OpenGL,
    Second Edition,
    Addison Wesley, 2000.

    Michael Barnsley,
    Fractals Everywhere,
    Academic Press, 1988,
    ISBN: 0120790696,
    LC: QA614.86.B37.

    Cleve Moler,
    Experiments with MATLAB,
    ebook: http:www.mathworks.com/moler/exm/index.html
*/
{
  int i;
  point2 p;
  int point_num = 500000;
  double prob[4] = { 0.85, 0.92, 0.99, 1.00 };
  double r;
  double x;
  double y;
/*
  Clear the window.
*/
  glClear ( GL_COLOR_BUFFER_BIT );
/*
  Compute and plot the points.
*/
  p[0] = drand48 ( );
  p[1] = drand48 ( );

  for ( i = 0; i < point_num; i++ )
  {
    r = drand48 ( );

    if ( r < prob[0] )
    {
      x =   0.85 * p[0] + 0.04 * p[1] + 0.0;
      y = - 0.04 * p[0] + 0.85 * p[1] + 1.6;
    }
    else if ( r < prob[1] )
    {
      x =   0.20 * p[0] - 0.26 * p[1] + 0.0;
      y =   0.23 * p[0] + 0.22 * p[1] + 1.6;
    }
    else if ( r < prob[2] )
    {
      x = - 0.15 * p[0] + 0.28 * p[1] + 0.0;
      y =   0.26 * p[0] + 0.24 * p[1] + 0.44;
    }
    else
    {
      x =   0.00 * p[0] + 0.00 * p[1] + 0.0;
      y =   0.00 * p[0] + 0.16 * p[1] + 0.0;
    }

    p[0] = x;
    p[1] = y;
/*
  Plot the new point.
*/
    glBegin ( GL_POINTS );
      glVertex2fv ( p );
    glEnd ( );
  }
/*
  Clear all buffers.
*/
  glFlush ( );

  return;
}
/******************************************************************************/

void myinit ( )

/******************************************************************************/
/*
  Purpose:

    MYINIT initializes OpenGL state variables dealing with viewing and attributes.

  Licensing:

    This code is distributed under the MIT license.

  Modified:

    09 May 2011

  Reference:

    Edward Angel,
    Interactive Computer Graphics:
    A Top-Down Approach with OpenGL,
    Second Edition,
    Addison Wesley, 2000.

    Michael Barnsley,
    Fractals Everywhere,
    Academic Press, 1988,
    ISBN: 0120790696,
    LC: QA614.86.B37.
*/
{
/*
  Set the background to WHITE.
*/
  glClearColor ( 1.0, 1.0, 1.0, 1.0 );
/*
  Draw in FOREST GREEN.
*/
  glColor3f ( 0.133, 0.545, 0.133 );
/*
  Set up a viewing window with origin at the lower left.
*/
  glMatrixMode ( GL_PROJECTION );
  glLoadIdentity ( );
  gluOrtho2D ( -4.0, 4.0, -1.0, 11.0 );
  glMatrixMode ( GL_MODELVIEW );

  return;
}