[sdiy] Digital simulation of the Lorenz attractor

[Jaroslaw Ziembicki]

Hi,
I wrote a C program that simulates the Lorenz attractor
and plots the results. The graphic mode should be set.
Here is the basic subroutine. Maybe somebody will find
it useful.
Regards
Jarek


void Lorenz(void)
{
/* simulation variables/parameters: */
  float x = 0.1;
  float y = 0.0;
  float z = 0.0;
  float s = 10.00;
  float r = 28.00;
  float b =  2.67;
  float dt = 100E-6;
/* graphics' variables/parameters: */
  float xxscale = 0.02*(float)(getmaxx()+1); /* for plot scaling */
  float yyscale = 0.01*(float)(getmaxy()+1); /* for plot scaling */
  WORD xx0 = (getmaxx()+1)/2;     /* plot center x */
  WORD yy0 = (getmaxy()+1)/2;     /* plot center y */
  WORD color = 15;

/* border, x and y axes: */
  setcolor(DARKGRAY);
  rectangle(0,0,getmaxx(),getmaxy());
  line(0,yy0,getmaxx(),yy0); line(xx0,0,xx0,getmaxx());
/* loop: */
  while ( kbhit() ) getch();
  do
  {
    float dx,dy,dz;
    WORD    xx,yy;

    /* put a pixel: */
    xx = xx0+(int)(xxscale*x); yy = yy0-(int)(yyscale*z);
    putpixel(xx,yy,color);
    /* new x,y,z values: */
    dx = dt * (s*(y-x));
    dy = dt * (r*x - y - x*z);
    dz = dt * (x*y - b*z);
    x += dx; y += dy; z += dz;
    /* next color: */
    color++; if ( color > 15 ) color = 0;
  }
  while ( !kbhit() );
}

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