//------------------------- DistToLineSegment ----------------------------
//
// given a line segment AB and a point P, this function calculates the
// perpendicular distance between them
//------------------------------------------------------------------------
public static double DistToLineSegment(Vector2D A,
Vector2D B,
Vector2D P)
{
//if the angle is obtuse between PA and AB is obtuse then the closest
//vertex must be A
double dotA = (P.X - A.X) * (B.X - A.X) + (P.Y - A.Y) * (B.Y - A.Y);
if (dotA <= 0)
{
return(Vector2D.Vec2DDistance(A, P));
}
//if the angle is obtuse between PB and AB is obtuse then the closest
//vertex must be B
double dotB = (P.X - B.X) * (A.X - B.X) + (P.Y - B.Y) * (A.Y - B.Y);
if (dotB <= 0)
{
return(Vector2D.Vec2DDistance(B, P));
}
//calculate the point along AB that is the closest to P
Vector2D Point = A + ((B - A) * dotA) / (dotA + dotB);
//calculate the distance P-Point
return(Vector2D.Vec2DDistance(P, Point));
}
//-------------------- LineIntersection2D-------------------------
//
// Given 2 lines in 2D space AB, CD this returns true if an
// intersection occurs and sets dist to the distance the intersection
// occurs along AB. Also sets the 2d vector point to the point of
// intersection
//-----------------------------------------------------------------
public static bool LineIntersection2D(Vector2D A,
Vector2D B,
Vector2D C,
Vector2D D,
ref double dist,
ref Vector2D point)
{
double rTop = (A.Y - C.Y) * (D.X - C.X) - (A.X - C.X) * (D.Y - C.Y);
double rBot = (B.X - A.X) * (D.Y - C.Y) - (B.Y - A.Y) * (D.X - C.X);
double sTop = (A.Y - C.Y) * (B.X - A.X) - (A.X - C.X) * (B.Y - A.Y);
double sBot = (B.X - A.X) * (D.Y - C.Y) - (B.Y - A.Y) * (D.X - C.X);
if ((rBot == 0) || (sBot == 0))
{
//lines are parallel
return(false);
}
double r = rTop / rBot;
double s = sTop / sBot;
if ((r > 0) && (r < 1) && (s > 0) && (s < 1))
{
dist = Vector2D.Vec2DDistance(A, B) * r;
point = A + (B - A) * r;
return(true);
}
else
{
dist = 0;
return(false);
}
}
//--------------------LineIntersection2D-------------------------
//
// Given 2 lines in 2D space AB, CD this returns true if an
// intersection occurs and sets dist to the distance the intersection
// occurs along AB
//
//-----------------------------------------------------------------
public static bool LineIntersection2D(Vector2D A,
Vector2D B,
Vector2D C,
Vector2D D,
ref double dist)
{
double rTop = (A.Y - C.Y) * (D.X - C.X) - (A.X - C.X) * (D.Y - C.Y);
double sTop = (A.Y - C.Y) * (B.X - A.X) - (A.X - C.X) * (B.Y - A.Y);
double Bot = (B.X - A.X) * (D.Y - C.Y) - (B.Y - A.Y) * (D.X - C.X);
if (Bot == 0)//parallel
{
if (isEqual(rTop, 0) && isEqual(sTop, 0))
{
return(true);
}
return(false);
}
double r = rTop / Bot;
double s = sTop / Bot;
if ((r > 0) && (r < 1) && (s > 0) && (s < 1))
{
dist = Vector2D.Vec2DDistance(A, B) * r;
return(true);
}
else
{
dist = 0;
return(false);
}
}