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
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
|
include <math.h>
# ME_ELLGEOM -- Given the semi-major axis, ratio of semi-minor to semi-major
# axes, and position angle, compute the parameters of the equation of the
# ellipse, where the ellipse is defined as A * X ** 2 + B * x * y +
# C * Y ** 2 - F = 0.
procedure me_ellgeom (a, ratio, theta, aa, bb, cc, ff)
real a #I the semi-major axis
real ratio #I the ratio of semi-minor to semi-major axes
real theta #I the position angle of the major axis
real aa #O the coefficient of x ** 2
real bb #O the coefficient of x * y
real cc #O the coefficient of y ** 2
real ff #O the constant term
real cost, sint, costsq, sintsq
real asq, bsq
begin
# Get the angles.
cost = cos (DEGTORAD(theta))
sint = sin (DEGTORAD(theta))
costsq = cost ** 2
sintsq = sint ** 2
# Compute the parameters of the outer ellipse.
asq = a ** 2
bsq = (ratio * a) ** 2
aa = bsq * costsq + asq * sintsq
bb = 2.0 * (bsq - asq) * cost * sint
cc = asq * costsq + bsq * sintsq
ff = asq * bsq
end
# ME_RECTGEOM -- Construct a polygon representation of a rotated rectangle
# givev the half-width of the long axis, the ratio of the half-width of the
# short axis to the long axis, and the rotation angle.
procedure me_rectgeom (hwidth, ratio, theta, xout, yout)
real hwidth #I the half-width of the long axis of the rectangle
real ratio #I the ratio of short to long axes of the rectangle
real theta #I the rotation angle
real xout[ARB] #O the x coordinates of the output vertices
real yout[ARB] #O the y coordinates of the output vertices
real cost, sint, x, y
begin
cost = cos (DEGTORAD(theta))
sint = sin (DEGTORAD(theta))
x = hwidth
y = ratio * x
xout[1] = x * cost - y * sint
yout[1] = x * sint + y * cost
x = -x
y = y
xout[2] = x * cost - y * sint
yout[2] = x * sint + y * cost
x = x
y = -y
xout[3] = x * cost - y * sint
yout[3] = x * sint + y * cost
x = -x
y = y
xout[4] = x * cost - y * sint
yout[4] = x * sint + y * cost
end
|
