Differences From Artifact [0f1f35288c2dfafe]:
- File
lib/geo/line_circle.cpp
- 2012-05-20 14:16:51 - part of checkin [2034908d41] on branch trunk - 543 (user: kinaba) [annotate]
To Artifact [f037935b3feedc1e]:
- File
lib/geo/circle.cpp
- 2013-06-30 08:35:05 - part of checkin [07ad2e1283] on branch trunk - Geocon library update. (user: kinaba) [annotate]
1 -typedef long double LD;
2 -typedef complex<LD> CMP;
1 +// Verified: partly by geocon2013 D(1).
3 2
4 -bool line_circle(CMP la, CMP lb, CMP c, LD r, CMP* p1, CMP* p2)
3 +// Crosspoing of a line (not lineseg!) and a circle).
4 +bool line_circle(CMP la, CMP lb, CMP c, double r, CMP* p1, CMP* p2)
5 5 {
6 6 CMP v = (lb-la) / abs(lb-la);
7 7 CMP o = (c-la) / v;
8 8 if( abs(o.imag()) > r )
9 9 return false;
10 - LD dx = sqrt(r*r - o.imag()*o.imag());
10 + double dx = sqrt(r*r - o.imag()*o.imag());
11 11 *p1 = la + (o.real()-dx)*v;
12 12 *p2 = la + (o.real()+dx)*v;
13 13 return true;
14 14 }
15 +
16 +// Whether or not |p| is in the circle (c, r).
17 +bool pt_in_circle(CMP p, CMP c, double r)
18 +{
19 + return norm(p-c) <= r*r;
20 +}
21 +
22 +// Assuming |o| is outside (C,r), compute the two tangent points.
23 +void sessen(CMP o, CMP c, double r, CMP* p1, CMP* p2)
24 +{
25 + double len = sqrt(norm(c-o) - r*r);
26 + double theta = asin(r/abs(c-o));
27 +
28 + if(p1) *p1 = o+(c-o)*polar(len/abs(c-o), theta);
29 + if(p2) *p2 = o+(c-o)*polar(len/abs(c-o), -theta);
30 +}
31 +
32 +// For two points |p| and |q| on (c,r), compute their distance along the circle.
33 +double d_on_c(CMP c, double r, CMP p, CMP q)
34 +{
35 + return abs(arg((p-c) / (q-c))) * r;
36 +}