/*!
*/
Vector2D
Line2D::intersection( const Line2D & line1,
const Line2D & line2 )
{
double tmp = line1.a() * line2.b() - line1.b() * line2.a();
if ( std::fabs( tmp ) < EPSILON )
{
return Vector2D::INVALIDATED;
}
return Vector2D( (line1.b() * line2.c() - line2.b() * line1.c()) / tmp,
(line2.a() * line1.c() - line1.a() * line2.c()) / tmp );
}
bool Box2D::intersect(const Line2D& line) const {
const double x1 = -(line.b()*topLeft_.v() + line.c())/line.a();
const double x2 = -(line.b()*bottomRight_.v() + line.c())/line.a();
if(x1 < topLeft_.u() && x2 < topLeft_.u()) return false;
if(x1 > bottomRight_.u() && x2 > bottomRight_.u()) return false;
const double y1 = -(line.a()*topLeft_.u() + line.c())/line.b();
const double y2 = -(line.a()*bottomRight_.u() + line.c())/line.b();
if(y1 < topLeft_.v() && y2 < topLeft_.v()) return false;
if(y1 > bottomRight_.v() && y2 > bottomRight_.v()) return false;
return true;
}
/*!
*/
bool
Segment2D::existIntersection( const Line2D & l ) const
{
double a0 = l.a() * origin().x + l.b() * origin().y + l.c();
double a1 = l.a() * terminal().x + l.b() * terminal().y + l.c();
return a0 * a1 <= 0.0;
}
/*!
*/
int
Circle2D::intersection( const Line2D & line,
Vector2D * sol1,
Vector2D * sol2 ) const
{
if ( std::fabs( line.a() ) < EPSILON )
{
if ( std::fabs( line.b() ) < EPSILON )
{
std::cerr << "Circle2D::intersection() illegal line."
<< std::endl;
return 0;
}
// Line: By + C = 0 ---> y = -C/B
// Circle: (x - cx)^2 + (y - cy)^2 = r^2
// --->
double x1 = 0.0, x2 = 0.0;
int n_sol
= QUADRATIC_FOMULA( 1.0,
-2.0 * center().x,
( SQUARE( center().x )
+ SQUARE( line.c() / line.b() + center().y )
- SQUARE( radius() ) ),
x1,
x2 );
if ( n_sol > 0 )
{
double y1 = -line.c() / line.b();
if ( sol1 )
{
sol1->assign( x1, y1 );
}
if ( n_sol > 1 && sol2 )
{
sol2->assign( x2, y1 );
}
}
return n_sol;
}
else
{
// include (fabs(l.b()) < EPSILON) case
// use line & circle formula
// Ax + By + C = 0
// (x - cx)^2 + (y - cy)^2 = r^2
// make y's quadratic formula using these fomula.
double m = line.b() / line.a();
double d = line.c() / line.a();
double a = 1.0 + m * m;
double b = 2.0 * ( -center().y + ( d + center().x ) * m );
double c = SQUARE( d + center().x )
+ SQUARE( center().y )
- SQUARE( radius() );
double y1 = 0.0, y2 = 0.0;
int n_sol = QUADRATIC_FOMULA( a, b, c,
y1, y2 );
if ( n_sol > 0 && sol1 )
{
sol1->assign( line.getX( y1 ), y1 );
}
if ( n_sol > 1 && sol2 )
{
sol2->assign( line.getX( y2 ), y2 );
}
return n_sol;
}
}
