lorenz1.c

/*
   Author:   Mitch Richling<http://www.mitchr.me>
   IP:       Copyright 1994 by Mitch Richling.  All rights reserved.
   Key word: lorenz strange attractor povray Euler
   Notes:    This is a very simple program to generate a curve based
             on Lorenz's attractor.  It uses Euler's method to solve the
             equations.  The "curve" consists of a series of spheres
             placed at each point found on the curve.  The spheres
             are connected with cylinders.  Note that this program 
             is simple enough to be coded with Povray itself.
*/

#include <stdio.h>

int main() {
  int maxBalls    = 10000;
  double tDelta   = 0.01;
  double x = 0.1;
  double y = 0.0;
  double z = 0;
  double a = 10;
  double b = 28;
  double c = 8.0 / 3.0;
  int numBalls;
  double xNew, yNew, zNew;
  fprintf(stderr, "Computation starting...\n");
  printf("sphere {<%f,%f,%f>, %f texture { crvTex } }\n", x, y, z, 0.2);
      
  for(numBalls=0;numBalls<maxBalls;numBalls++) {
    xNew = x + a*(y-x)*tDelta;
    yNew = y + (x*(b-z)-y)*tDelta;
    zNew = z + (x*y-c*z)*tDelta;

    /* Display 20 "status" messages. */
    if((numBalls % (int)(maxBalls/20)) == 0)
      fprintf(stderr, "Step: %6d  tDelta: %15.3f x: %15.2f y: %15.2f z: %15.2f\n", numBalls, tDelta, x, y, z);

    printf("sphere {<%f,%f,%f>, %f texture { crvTex } }\n", xNew, yNew, zNew, 0.1);
    printf("cylinder {<%f,%f,%f>, <%f,%f,%f>, %f texture { crvTex } }\n", x, y, z, xNew, yNew, zNew, 0.2);
    
    x=xNew;
    y=yNew;
    z=zNew;
  }
}