--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mupdf-source/thirdparty/freeglut/progs/demos/Lorenz/lorenz.c	Mon Sep 15 11:43:07 2025 +0200
@@ -0,0 +1,378 @@
+/*
+ * Lorenz Strange Attractor
+ *
+ * Written by John F. Fay in honor of the "freeglut" 2.0.0 release in July 2003
+ *
+ * What it does:
+ *  This program starts with two particles right next to each other.  The particles
+ *  move through a three-dimensional phase space governed by the following equations:
+ *       dx/dt = sigma * ( y - x )
+ *       dy/dt = r * x - y + x * z
+ *       dz/dt = x * y + b * z
+ *  These are the Lorenz equations and define the "Lorenz Attractor."  Any two particles
+ *  arbitrarily close together will move apart as time increases, but their tracks are
+ *  confined within a region of the space.
+ *
+ * Commands:
+ *  Arrow keys:  Rotate the view
+ *  PgUp, PgDn:  Zoom in and out
+ *  Mouse click:  Center on the nearest point on a particle trajectory
+ *
+ *  'r'/'R':  Reset the simulation
+ *  'm'/'M':  Modify the Lorenz parameters (in the text window)
+ *  's'/'S':  Stop (the advancement in time)
+ *  'g'/'G':  Go
+ *  <spacebar>:  Single-step
+ *  <Escape>:  Quit
+ */
+
+/* Include Files */
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdarg.h>
+#include <string.h>
+#include <math.h>
+#include <GL/freeglut.h>
+#ifdef _MSC_VER
+/* DUMP MEMORY LEAKS */
+#include <crtdbg.h>
+#endif
+
+
+/************************************** Defined Constants ***************************************/
+/* Number of points to draw in the curves */
+#define NUM_POINTS    512
+
+/* Angle to rotate when the user presses an arrow key */
+#define ROTATION_ANGLE  5.0
+
+/* Amount to scale bu when the user presses PgUp or PgDn */
+#define SCALE_FACTOR     0.8
+
+
+/*************************************** Global Variables ***************************************/
+/* Lorenz Attractor variables */
+double s0 = 10.0, r0 = 28.0, b0 = 8.0/3.0 ;   /* Default Lorenz attactor parameters */
+double time_step = 0.03 ;                     /* Time step in the simulation */
+double sigma = 10.0, r = 28.0, b = 8.0/3.0 ;  /* Lorenz attactor parameters */
+double red_position[NUM_POINTS][3] ;          /* Path of the red point */
+double grn_position[NUM_POINTS][3] ;          /* Path of the green point */
+int array_index ;                             /* Position in *_position arrays of most recent point */
+double distance = 0.0 ;                       /* Distance between the two points */
+
+/* GLUT variables */
+double yaw = 0.0, pit = 0.0 ;                 /* Euler angles of the viewing rotation */
+double scale = 1.0 ;                          /* Scale factor */
+double xcen = 0.0, ycen = 0.0, zcen = 0.0 ;   /* Coordinates of the point looked at */
+
+int animate = 1 ;                             /* 0 - stop, 1 = go, 2 = single-step */
+
+
+/******************************************* Functions ******************************************/
+
+/* The Lorenz Attractor */
+void calc_deriv ( double position[3], double deriv[3] )
+{
+  /* Calculate the Lorenz attractor derivatives */
+  deriv[0] = sigma * ( position[1] - position[0] ) ;
+  deriv[1] = ( r + position[2] ) * position[0] - position[1] ;
+  deriv[2] = -position[0] * position[1] - b * position[2] ;
+}
+
+void advance_in_time ( double time_step, double position[3], double new_position[3] )
+{
+  /* Move a point along the Lorenz attractor */
+  double deriv0[3], deriv1[3], deriv2[3], deriv3[3] ;
+  int i ;
+  memcpy ( new_position, position, 3 * sizeof(double) ) ;  /* Save the present values */
+
+  /* First pass in a Fourth-Order Runge-Kutta integration method */
+  calc_deriv ( position, deriv0 ) ;
+  for ( i = 0; i < 3; i++ )
+    new_position[i] = position[i] + 0.5 * time_step * deriv0[i] ;
+
+  /* Second pass */
+  calc_deriv ( new_position, deriv1 ) ;
+  for ( i = 0; i < 3; i++ )
+    new_position[i] = position[i] + 0.5 * time_step * deriv1[i] ;
+
+  /* Third pass */
+  calc_deriv ( position, deriv2 ) ;
+  for ( i = 0; i < 3; i++ )
+    new_position[i] = position[i] + time_step * deriv2[i] ;
+
+  /* Second pass */
+  calc_deriv ( new_position, deriv3 ) ;
+  for ( i = 0; i < 3; i++ )
+    new_position[i] = position[i] + 0.1666666666666666667 * time_step *
+                      ( deriv0[i] + 2.0 * ( deriv1[i] + deriv2[i] ) + deriv3[i] ) ;
+}
+
+static void
+checkedFGets ( char *s, int size, FILE *stream )
+{
+  if ( fgets ( s, size, stream ) == NULL ) {
+    fprintf ( stderr, "fgets failed\n");
+    exit ( EXIT_FAILURE );
+  }
+}
+
+
+/* GLUT callbacks */
+
+#define INPUT_LINE_LENGTH 80
+
+void key_cb ( unsigned char key, int x, int y )
+{
+  int i ;
+  char inputline [ INPUT_LINE_LENGTH ] ;
+
+  switch ( key )
+  {
+  case 'r' :  case 'R' :  /* Reset the simulation */
+    /* Reset the Lorenz parameters */
+    sigma = s0 ;
+    b = b0 ;
+    r = r0 ;
+    /* Set an initial position */
+    red_position[0][0] = (double)rand() / (double)RAND_MAX ;
+    red_position[0][1] = (double)rand() / (double)RAND_MAX ;
+    red_position[0][2] = (double)rand() / (double)RAND_MAX ;
+    grn_position[0][0] = (double)rand() / (double)RAND_MAX ;
+    grn_position[0][1] = (double)rand() / (double)RAND_MAX ;
+    grn_position[0][2] = (double)rand() / (double)RAND_MAX ;
+    array_index = 0 ;
+    /* Initialize the arrays */
+    for ( i = 1; i < NUM_POINTS; i++ )
+    {
+      memcpy ( red_position[i], red_position[0], 3 * sizeof(double) ) ;
+      memcpy ( grn_position[i], grn_position[0], 3 * sizeof(double) ) ;
+    }
+
+    break ;
+
+  case 'm' :  case 'M' :  /* Modify the Lorenz parameters */
+    printf ( "Please enter new value for <sigma> (default %f, currently %f): ", s0, sigma ) ;
+    checkedFGets ( inputline, sizeof ( inputline ), stdin ) ;
+    sscanf ( inputline, "%lf", &sigma ) ;
+
+    printf ( "Please enter new value for <b> (default %f, currently %f): ", b0, b ) ;
+    checkedFGets ( inputline, sizeof ( inputline ), stdin ) ;
+    sscanf ( inputline, "%lf", &b ) ;
+
+    printf ( "Please enter new value for <r> (default %f, currently %f): ", r0, r ) ;
+    checkedFGets ( inputline, sizeof ( inputline ), stdin ) ;
+    sscanf ( inputline, "%lf", &r ) ;
+
+    break ;
+
+  case 's' :  case 'S' :  /* Stop the animation */
+    animate = 0 ;
+    break ;
+
+  case 'g' :  case 'G' :  /* Start the animation */
+    animate = 1 ;
+    break ;
+
+  case ' ' :  /* Spacebar:  Single step */
+    animate = 2 ;
+    break ;
+
+  case 27 :  /* Escape key */
+    glutLeaveMainLoop () ;
+    break ;
+  }
+}
+
+void special_cb ( int key, int x, int y )
+{
+  switch ( key )
+  {
+  case GLUT_KEY_UP :  /* Rotate up a little */
+    glRotated ( ROTATION_ANGLE, 0.0, 1.0, 0.0 ) ;
+    break ;
+
+  case GLUT_KEY_DOWN :  /* Rotate down a little */
+    glRotated ( -ROTATION_ANGLE, 0.0, 1.0, 0.0 ) ;
+    break ;
+
+  case GLUT_KEY_LEFT :  /* Rotate left a little */
+    glRotated ( ROTATION_ANGLE, 0.0, 0.0, 1.0 ) ;
+    break ;
+
+  case GLUT_KEY_RIGHT :  /* Rotate right a little */
+    glRotated ( -ROTATION_ANGLE, 0.0, 0.0, 1.0 ) ;
+    break ;
+
+  case GLUT_KEY_PAGE_UP :  /* Zoom in a little */
+    glScaled ( 1.0 / SCALE_FACTOR, 1.0 / SCALE_FACTOR, 1.0 / SCALE_FACTOR ) ;
+    break ;
+
+  case GLUT_KEY_PAGE_DOWN :  /* Zoom out a little */
+    glScaled ( SCALE_FACTOR, SCALE_FACTOR, SCALE_FACTOR ) ;
+    break ;
+  }
+
+  glutPostRedisplay () ;
+}
+
+void mouse_cb ( int button, int updown, int x, int y )
+{
+  if ( updown == GLUT_DOWN )
+  {
+    /*double dist = 1.0e20 ;   A very large number */
+    /* The idea here is that we go into "pick" mode and pick the nearest point
+       to the mouse click position.  Unfortunately I don't have the time to implement
+       it at the moment. */
+  }
+}
+
+void draw_curve ( int index, double position [ NUM_POINTS ][3] )
+{
+  int i = index ;
+
+  glBegin ( GL_LINE_STRIP ) ;
+  do
+  {
+    i = ( i == NUM_POINTS-1 ) ? 0 : i + 1 ;
+    glVertex3dv ( position[i] ) ;
+  }
+  while ( i != index ) ;
+
+  glEnd () ;
+}
+
+void bitmapPrintf (const char *fmt, ...)
+{
+    static char buf[256];
+    va_list args;
+
+    va_start(args, fmt);
+#if defined(WIN32) && !defined(__CYGWIN__)
+    (void) _vsnprintf (buf, sizeof(buf), fmt, args);
+#else
+    (void) vsnprintf (buf, sizeof(buf), fmt, args);
+#endif
+    va_end(args);
+    glutBitmapString ( GLUT_BITMAP_HELVETICA_12, (unsigned char*)buf ) ;
+}
+
+void display_cb ( void )
+{
+  glClear ( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ) ;
+
+  glColor3d ( 1.0, 1.0, 1.0 ) ;  /* White */
+  /* Draw some axes */
+  glBegin ( GL_LINES ) ;
+  glVertex3d ( 0.0, 0.0, 0.0 ) ;
+  glVertex3d ( 2.0, 0.0, 0.0 ) ;
+  glVertex3d ( 0.0, 0.0, 0.0 ) ;
+  glVertex3d ( 0.0, 1.0, 0.0 ) ;
+  glVertex3d ( 0.0, 0.0, 0.0 ) ;
+  glVertex3d ( 0.0, 0.0, 1.0 ) ;
+  glEnd () ;
+
+  glColor3d ( 1.0, 0.0, 0.0 ) ;  /* Red */
+  draw_curve ( array_index, red_position ) ;
+
+  glColor3d ( 0.0, 1.0, 0.0 ) ;  /* Green */
+  draw_curve ( array_index, grn_position ) ;
+
+  /* Print the distance between the two points */
+  glColor3d ( 1.0, 1.0, 1.0 ) ;  /* White */
+  glRasterPos2i ( 1, 1 ) ;
+  bitmapPrintf ( "Distance: %10.6f", distance ) ;
+
+  glutSwapBuffers();
+}
+
+void reshape_cb ( int width, int height )
+{
+  float ar;
+  glViewport ( 0, 0, width, height ) ;
+  glMatrixMode ( GL_PROJECTION ) ;
+  glLoadIdentity () ;
+  ar = (float) width / (float) height ;
+  glFrustum ( -ar, ar, -1.0, 1.0, 10.0, 100.0 ) ;
+  glMatrixMode ( GL_MODELVIEW ) ;
+  glLoadIdentity () ;
+  xcen = 0.0 ;
+  ycen = 0.0 ;
+  zcen = 0.0 ;
+  glTranslated ( xcen, ycen, zcen - 50.0 ) ;
+}
+
+
+void timer_cb ( int value )
+{
+  /* Function called at regular intervals to update the positions of the points */
+  double deltax, deltay, deltaz ;
+  int new_index = array_index + 1 ;
+
+  /* Set the next timed callback */
+  glutTimerFunc ( 30, timer_cb, 0 ) ;
+
+  if ( animate > 0 )
+  {
+    if ( new_index == NUM_POINTS ) new_index = 0 ;
+    advance_in_time ( time_step, red_position[array_index], red_position[new_index] ) ;
+    advance_in_time ( time_step, grn_position[array_index], grn_position[new_index] ) ;
+    array_index = new_index ;
+
+    deltax = red_position[array_index][0] - grn_position[array_index][0] ;
+    deltay = red_position[array_index][1] - grn_position[array_index][1] ;
+    deltaz = red_position[array_index][2] - grn_position[array_index][2] ;
+    distance = sqrt ( deltax * deltax + deltay * deltay + deltaz * deltaz ) ;
+
+    if ( animate == 2 ) animate = 0 ;
+  }
+
+  glutPostRedisplay () ;
+}
+
+
+
+/* The Main Program */
+
+int main ( int argc, char *argv[] )
+{
+  int pargc = argc ;
+
+  /* Initialize the random number generator */
+  srand ( 1023 ) ;
+
+  /* Set up the OpenGL parameters */
+  glEnable ( GL_DEPTH_TEST ) ;
+  glClearColor ( 0.0, 0.0, 0.0, 0.0 ) ;
+  glClearDepth ( 1.0 ) ;
+
+  /* Initialize GLUT */
+  glutInitWindowSize ( 600, 600 ) ;
+  glutInit ( &pargc, argv ) ;
+  glutInitDisplayMode ( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH ) ;
+
+  /* Create the window */
+  glutCreateWindow ( "Lorenz Attractor" ) ;
+  glutKeyboardFunc ( key_cb ) ;
+  glutMouseFunc ( mouse_cb ) ;
+  glutSpecialFunc ( special_cb ) ;
+  glutDisplayFunc ( display_cb ) ;
+  glutReshapeFunc ( reshape_cb ) ;
+  glutTimerFunc ( 30, timer_cb, 0 ) ;
+
+  /* Initialize the attractor:  The easiest way is to call the keyboard callback with an
+   * argument of 'r' for Reset.
+   */
+  key_cb ( 'r', 0, 0 ) ;
+
+  /* Enter the GLUT main loop */
+  glutMainLoop () ;
+
+#ifdef _MSC_VER
+  /* DUMP MEMORY LEAK INFORMATION */
+  _CrtDumpMemoryLeaks () ;
+#endif
+
+  return 0 ;
+}
+