rotate.c

/*
 * rotate.c
 * 
 */
#include "copyright2.h"

#include <stdio.h>
#include <math.h>
#include "netrek.h"

#ifdef ROTATERACE

void
rotate_dir(d, r)
    unsigned char  *d;
    int             r;
{
   (*d) += r;
}

/* general rotation */

void
rotate_coord(x, y, d, cx, cy)
    int            *x, *y;	/* values used and returned */
    int             d;		/* degree (pi == 128) */
    int             cx, cy;	/* around center point */
{
   register
   int             ox, oy;

   ox = *x;
   oy = *y;

   switch (d) {

   case 0:
      return;

   case 64:
   case -192:
      *x = cy - oy + cx;
      *y = ox - cx + cy;
      break;

   case 128:
   case -128:
      *x = cx - ox + cx;
      *y = cy - oy + cy;
      break;

   case 192:
   case -64:
      *x = oy - cy + cx;
      *y = cx - ox + cy;
      break;

   default:{
	 /* do it the hard way */
	 double          dir;
	 double          r, dx, dy;
	 double          rd = (double) d * 3.1415927 / 128.;

	 if (*x != cx || *y != cy) {
	    dx = (double) (*x - cx);
	    dy = (double) (cy - *y);
	    dir = atan2(dx, dy) - 3.1415927 / 2.;
	    r = hypot(dx, dy);
	    dir += rd;
	    *x = (int) (r * cos(dir) + cx);
	    *y = (int) (r * sin(dir) + cy);
	 }
      }
   }
}
#endif