attachment:t41.c of ToroidalOrbits

   1 // t41.c
   2 // v0.1 KHL 2009-04-21
   3 // gcc -o t41 t41.c -lm -lgd ; ./t41
   4 // static drawing, though slow to compute
   5 // earth and toroid around orbit
   6 
   7 #define TITLE    "Orbit map, 500km minor radius"
   8 #define GIFOUT   "t41.gif"
   9 #define RADIUS   500.00
  10 #define SQUARE    10.00
  11 #define SCALE    0.5
  12 
  13 #include "tor00.hc"
  14 
  15 int main () {
  16    int     diam = (int) ( 2.0 * SCALE * RADIUS );
  17    double  rmax = (RADIUS/SQUARE)-0.51 ;
  18    int     ymax = (int) rmax ;
  19    int     xmax   ;
  20    int     delta = (int) ( SCALE * SQUARE + 0.001 );
  21    int     sq    = (delta / 2) - 1 ;
  22    int     num = 0 ;
  23    int     xp, yp ;
  24    int     ycent = YCENTER - 25 ;
  25 
  26    displaystart();
  27    torstart();
  28    gdImageGifAnimBegin( im1, gifout, 1, -1 ) ; // no repeat
  29    // gdImageGifAnimBegin( im1, gifout, 1,  4 ) ; // repeat 4 times
  30    // gdImageGifAnimBegin( im1, gifout, 1,  0 ) ; // continuous repeat
  31    framestart(    90, TITLE );
  32 
  33    gdImageFilledEllipse( im, XCENTER, ycent, diam, diam, white );
  34 
  35    for( yp = -ymax ; yp <= ymax ; yp++ ) {
  36       xmax = (int) sqrt( rmax*rmax - (double) (yp*yp) );
  37       int y = yp*delta + ycent ;
  38       for( xp = -xmax ; xp <= xmax ; xp++ ) { 
  39          int x = xp*delta + XCENTER ;
  40          num++ ;
  41          gdImageFilledRectangle( im, x-sq, y-sq, x+sq, y+sq, black );
  42       }
  43   }
  44   sprintf( bottom, "%6d orbits,%3.0fkm spacing between orbits", num, SQUARE );
  45 
  46   frameend();
  47   displayend();
  48   return 0;
  49 }