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; | 1 // Verified: partly by geocon2013 D(1).
2 typedef complex<LD> CMP; <
3 2
> 3 // Crosspoing of a line (not lineseg!) and a circle).
4 bool line_circle(CMP la, CMP lb, CMP c, LD r, CMP* p1, CMP* p2) | 4 bool line_circle(CMP la, CMP lb, CMP c, double r, CMP* p1, CMP* p2)
5 { 5 {
6 CMP v = (lb-la) / abs(lb-la); 6 CMP v = (lb-la) / abs(lb-la);
7 CMP o = (c-la) / v; 7 CMP o = (c-la) / v;
8 if( abs(o.imag()) > r ) 8 if( abs(o.imag()) > r )
9 return false; 9 return false;
10 LD dx = sqrt(r*r - o.imag()*o.imag()); | 10 double dx = sqrt(r*r - o.imag()*o.imag());
11 *p1 = la + (o.real()-dx)*v; 11 *p1 = la + (o.real()-dx)*v;
12 *p2 = la + (o.real()+dx)*v; 12 *p2 = la + (o.real()+dx)*v;
13 return true; 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 }