blob: b2ee42b7152c37ce0227f8e69febedefe034674e (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
|
# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <math.h>
define PIOVER4 (0.25 * PI)
define THREEPIOVER4 (0.75 * TWOPI)
# RPTHETA4 -- Polar angle, Real precision, 4 arguments; from p1(x,y) to p2(x,y):
# angle between line segment p1-p2 and horizontal +x axis centered on p1;
# returned in radians; single precision (see pdtheta4).
real procedure rptheta4 (p1x, p1y, p2x, p2y)
real p1x,p1y, p2x,p2y # x,y of each point
real dx, dy, ang
begin
dx = p2x - p1x
dy = p2y - p1y
if (dx == 0.0) {
if (dy >= 0.0) {
ang = HALFPI
} else {
ang = THREEPIOVER4
}
} else {
ang = atan (dy / dx)
if (dx < 0.0) { # 2nd or 3rd quadrant
ang = ang + PI
} else if (dy < 0.0) { # 4th quadrant
ang = ang + TWOPI
}
}
return (ang)
end
|
