1 28994509 2004-04-21 devnull #include <u.h>
 2 28994509 2004-04-21 devnull #include <libc.h>
 3 28994509 2004-04-21 devnull #include "map.h"
 4 28994509 2004-04-21 devnull 
 5 28994509 2004-04-21 devnull #define ORTHRAD 1000
 6 28994509 2004-04-21 devnull static double viewpt;
 7 28994509 2004-04-21 devnull 
 8 28994509 2004-04-21 devnull static int
 9 28994509 2004-04-21 devnull Xperspective(struct place *place, double *x, double *y)
10 28994509 2004-04-21 devnull {
11 28994509 2004-04-21 devnull 	double r;
12 310ae033 2017-01-06 rsc 	if(viewpt<=1+FUZZ && fabs(place->nlat.s)<=viewpt+.01)
13 28994509 2004-04-21 devnull 		return(-1);
14 28994509 2004-04-21 devnull 	r = place->nlat.c*(viewpt - 1.)/(viewpt - place->nlat.s);
15 28994509 2004-04-21 devnull 	*x = - r*place->wlon.s;
16 28994509 2004-04-21 devnull 	*y = - r*place->wlon.c;
17 28994509 2004-04-21 devnull 	if(r>4.)
18 28994509 2004-04-21 devnull 		return(-1);
19 28994509 2004-04-21 devnull 	if(fabs(viewpt)>1 && place->nlat.s<1/viewpt ||
20 28994509 2004-04-21 devnull 	   fabs(viewpt)<=1 && place->nlat.s<viewpt)
21 28994509 2004-04-21 devnull 			return 0;
22 28994509 2004-04-21 devnull 	return(1);
23 28994509 2004-04-21 devnull }
24 28994509 2004-04-21 devnull 
25 28994509 2004-04-21 devnull proj
26 28994509 2004-04-21 devnull perspective(double radius)
27 28994509 2004-04-21 devnull {
28 28994509 2004-04-21 devnull 	viewpt = radius;
29 28994509 2004-04-21 devnull 	if(viewpt >= ORTHRAD)
30 28994509 2004-04-21 devnull 		return(Xorthographic);
31 28994509 2004-04-21 devnull 	if(fabs(viewpt-1.)<.0001)
32 28994509 2004-04-21 devnull 		return(0);
33 28994509 2004-04-21 devnull 	return(Xperspective);
34 28994509 2004-04-21 devnull }
35 28994509 2004-04-21 devnull 
36 28994509 2004-04-21 devnull 	/* called from various conformal projections,
37 28994509 2004-04-21 devnull            but not from stereographic itself */
38 28994509 2004-04-21 devnull int
39 28994509 2004-04-21 devnull Xstereographic(struct place *place, double *x, double *y)
40 28994509 2004-04-21 devnull {
41 28994509 2004-04-21 devnull 	double v = viewpt;
42 28994509 2004-04-21 devnull 	int retval;
43 28994509 2004-04-21 devnull 	viewpt = -1;
44 28994509 2004-04-21 devnull 	retval = Xperspective(place, x, y);
45 28994509 2004-04-21 devnull 	viewpt = v;
46 28994509 2004-04-21 devnull 	return retval;
47 28994509 2004-04-21 devnull }
48 28994509 2004-04-21 devnull 
49 28994509 2004-04-21 devnull proj
50 28994509 2004-04-21 devnull stereographic(void)
51 28994509 2004-04-21 devnull {
52 28994509 2004-04-21 devnull 	viewpt = -1.;
53 28994509 2004-04-21 devnull 	return(Xperspective);
54 28994509 2004-04-21 devnull }
55 28994509 2004-04-21 devnull 
56 28994509 2004-04-21 devnull proj
57 28994509 2004-04-21 devnull gnomonic(void)
58 28994509 2004-04-21 devnull {
59 28994509 2004-04-21 devnull 	viewpt = 0.;
60 28994509 2004-04-21 devnull 	return(Xperspective);
61 28994509 2004-04-21 devnull }
62 28994509 2004-04-21 devnull 
63 28994509 2004-04-21 devnull int
64 28994509 2004-04-21 devnull plimb(double *lat, double *lon, double res)
65 28994509 2004-04-21 devnull {
66 28994509 2004-04-21 devnull 	static int first = 1;
67 28994509 2004-04-21 devnull 	if(viewpt >= ORTHRAD)
68 28994509 2004-04-21 devnull 		return olimb(lat, lon, res);
69 28994509 2004-04-21 devnull 	if(first) {
70 28994509 2004-04-21 devnull 		first = 0;
71 28994509 2004-04-21 devnull 		*lon = -180;
72 28994509 2004-04-21 devnull 		if(fabs(viewpt) < .01)
73 28994509 2004-04-21 devnull 			*lat = 0;
74 28994509 2004-04-21 devnull 		else if(fabs(viewpt)<=1)
75 28994509 2004-04-21 devnull 			*lat = asin(viewpt)/RAD;
76 28994509 2004-04-21 devnull 		else
77 28994509 2004-04-21 devnull 			*lat = asin(1/viewpt)/RAD;
78 28994509 2004-04-21 devnull 	} else
79 28994509 2004-04-21 devnull 		*lon += res;
80 28994509 2004-04-21 devnull 	if(*lon <= 180)
81 28994509 2004-04-21 devnull 		return 1;
82 28994509 2004-04-21 devnull 	first = 1;
83 28994509 2004-04-21 devnull 	return -1;
84 28994509 2004-04-21 devnull }