attachment:t28.c of ToroidalOrbits

   1 // t28.c
   2 // v0.1 KHL 2009-04-21
   3 // gcc -o t28 t28.c -lm -lgd ; ./t28
   4 // static drawing, though slow to compute
   5 // earth and toroid around orbit
   6 
   7 #define TITLE    "M288, 7693 orbits, 500km minor radius"
   8 #define GIFOUT   "t28.gif"
   9 #define NORB    -24
  10 #define DELTANG 0.2
  11 #define ORBWIDTH  9
  12 #define ANG0      0
  13 #define ANG1     90
  14 #define ANG2    142
  15 #define NELIP    32
  16 #define RADIUS   0.07839            // 500/6378
  17 
  18 #include "tor00.hc"
  19 
  20 int main () {
  21    double  t_ang ;
  22    int     e_cnt ;
  23    int     orb ;
  24 
  25    gdPoint ellipse0[NELIP+2];
  26    gdPoint ellipse1[NELIP+2];
  27 
  28    displaystart();
  29 
  30    torstart();
  31 
  32    gdImageGifAnimBegin( im1, gifout, 1, -1 ) ; // no repeat
  33    // gdImageGifAnimBegin( im1, gifout, 1,  4 ) ; // repeat 4 times
  34    // gdImageGifAnimBegin( im1, gifout, 1,  0 ) ; // continuous repeat
  35 
  36    framestart(    90, TITLE );
  37 
  38    // draw back portion of the orbit toroid
  39   
  40    double acolor =  0.0 ;
  41 
  42    for( t_ang=ANG0 ; t_ang < ANG2 ; t_ang += DELTANG ) {
  43 
  44       double ecolor ;
  45       if( acolor < 0.5 ) { ecolor = gray ; }
  46       else {
  47          ecolor = lgray ;
  48          if( acolor > 14.5 ) { acolor -= 15.0 ; }
  49       }
  50       acolor += DELTANG ;
  51 
  52       double angle_rad=DEG2RAD( t_ang );
  53 
  54       // ellipse disk - since it is at an angle, we will have to draw it
  55       // as a filled polygon
  56     
  57       // ellipse disk on left
  58       for( e_cnt=0 ; e_cnt < NELIP ; e_cnt++ ) {
  59          double toa = angle_rad + (2.0*PI*e_cnt)/NELIP  ;
  60          double tos = RADIUS          ;
  61          double tor = tos * cos( toa );
  62          double toy = tos * sin( toa );
  63          double tox = -(major+tor)*sin( angle_rad );
  64 	 double toz = -(major+tor)*cos( angle_rad );
  65 	 ellipse0[e_cnt] = sr0( tox, toy, toz );
  66       }
  67       gdImagePolygon( im, ellipse0, NELIP, ecolor );
  68 
  69       // ellipse disk on right
  70       for( e_cnt=0 ; e_cnt < NELIP ; e_cnt++ ) {
  71          double toa = -angle_rad + (2.0*PI*e_cnt)/NELIP  ;
  72          double tos = RADIUS          ;
  73          double tor = tos * cos( toa );
  74          double toy = tos * sin( toa );
  75          double tox = -(major+tor)*sin( -angle_rad );
  76          double toz = -(major+tor)*cos( -angle_rad );
  77          ellipse1[e_cnt] = sr0( tox, toy, toz );
  78       }
  79       gdImagePolygon( im, ellipse1, NELIP, ecolor );
  80    }
  81 
  82    gdImageFilledPolygon( im, ellipse0, NELIP, gray );
  83    gdImagePolygon( im, ellipse0, NELIP, lgray  );
  84 
  85    gdImageFilledPolygon( im, ellipse1, NELIP, gray );
  86    gdImagePolygon( im, ellipse1, NELIP, lgray  );
  87 
  88    drawearth();
  89    sprintf( bottom, "10km spacing between orbits" );
  90 
  91    frameend();
  92    displayend();
  93    return 0;
  94 }