/// <summary>
/// Returns a vertex representing the closest point on this line segment from a given vertex
/// </summary>
/// <param name="point">The point we want to be close to</param>
/// <param name="isInfiniteLine">If true treat the line as infinitly long</param>
/// <param name="endPointFlag">Outputs 0 if the vertex is on the line segment, 1 if beyond P0, 2 if beyong P1 and -1 if P1=P2</param>
/// <returns>The point on this segment or infinite line that is closest to the given point</returns>
public Vertex ClosestPointTo(Vertex point, bool isInfiniteLine, out EndPointInteraction endPointFlag)
{
// If the points defining this segment are the same, we treat the segment as a point
// special handling to avoid 0 in denominator later
if (P2.X == P1.X && P2.Y == P1.Y)
{
endPointFlag = EndPointInteraction.P1equalsP2;
return(P1);
}
//http://softsurfer.com/Archive/algorithm_0102/algorithm_0102.htm
Vector v = ToVector(); // vector from p1 to p2 in the segment
v.Z = 0;
Vector w = new Vector(P1.ToCoordinate(), point.ToCoordinate()); // vector from p1 to Point
w.Z = 0;
double c1 = w.Dot(v); // the dot product represents the projection onto the line
if (c1 < 0)
{
endPointFlag = EndPointInteraction.PastP1;
if (!isInfiniteLine) // The closest point on the segment to Point is p1
{
return(P1);
}
}
double c2 = v.Dot(v);
if (c2 <= c1)
{
endPointFlag = EndPointInteraction.PastP2;
if (!isInfiniteLine) // The closest point on the segment to Point is p2
{
return(P2);
}
}
// The closest point on the segment is perpendicular to the point,
// but somewhere on the segment between P1 and P2
endPointFlag = EndPointInteraction.OnLine;
double b = c1 / c2;
v = v.Multiply(b);
Vertex pb = new Vertex(P1.X + v.X, P1.Y + v.Y);
return(pb);
}
/// <summary>
/// Returns a vertex representing the closest point on this line segment from a given vertex
/// </summary>
/// <param name="point">The point we want to be close to</param>
/// <param name="isInfiniteLine">If true treat the line as infinitly long</param>
/// <param name="endPointFlag">Outputs 0 if the vertex is on the line segment, 1 if beyond P0, 2 if beyong P1 and -1 if P1=P2</param>
/// <returns>The point on this segment or infinite line that is closest to the given point</returns>
public Vertex ClosestPointTo(Vertex point, bool isInfiniteLine, out EndPointInteraction endPointFlag)
{
// If the points defining this segment are the same, we treat the segment as a point
// special handling to avoid 0 in denominator later
if (P2.X == P1.X && P2.Y == P1.Y)
{
endPointFlag = EndPointInteraction.P1equalsP2;
return P1;
}
//http://softsurfer.com/Archive/algorithm_0102/algorithm_0102.htm
Vector v = ToVector(); // vector from p1 to p2 in the segment
v.Z = 0;
Vector w = new Vector(P1.ToCoordinate(), point.ToCoordinate()); // vector from p1 to Point
w.Z = 0;
double c1 = w.Dot(v); // the dot product represents the projection onto the line
if (c1 < 0)
{
endPointFlag = EndPointInteraction.PastP1;
if (!isInfiniteLine) // The closest point on the segment to Point is p1
return P1;
}
double c2 = v.Dot(v);
if (c2 <= c1)
{
endPointFlag = EndPointInteraction.PastP2;
if (!isInfiniteLine) // The closest point on the segment to Point is p2
return P2;
}
// The closest point on the segment is perpendicular to the point,
// but somewhere on the segment between P1 and P2
endPointFlag = EndPointInteraction.OnLine;
double b = c1 / c2;
v = v.Multiply(b);
Vertex pb = new Vertex(P1.X + v.X, P1.Y + v.Y);
return pb;
}
