public Side GetSide(Vector2D pt)
{
return((Side)Math.Sign(StartToEnd.Cross(pt - Start)));
/*
* //its the basic idea of the crossproduct in R3 with a garuanteed 0 for z.
* return (Side)Math.Sign(Start.X * (End.Y - pt.Y) + End.X * (pt.Y - Start.Y) + pt.X * (Start.Y - End.Y));*/
}
public float GetIntersectionRatio(Vector2D start, Vector2D dir)
{
//see IsIntersecting...
Vector2D s = Start - start;
float denom = StartToEnd.Cross(dir);
return(dir.Cross(s) / denom);
}
/**
* Returns the sample ratio where this line would intersect the other. Segment boundaries are not considered.
*/
public float GetIntersectionRatio(LineSegment2D other)
{
//see IsIntersecting...
Vector2D ov = other.StartToEnd;
Vector2D s = Start - other.Start;
float denom = StartToEnd.Cross(ov);
return(ov.Cross(s) / denom);
}
/**
* Project the vector v on this line segment and return the ratio.
* return = 0 v = start
* return = 1 v = end
* return < 0 v is on the backward extension of AB
* return > 1 v is on the forward extension of AB
* 0< return <1 v is interior to AB
*/
public float GetSnapRatio(Vector2D v)
{
/*
* Let the point be C (Cx,Cy) and the line be AB (Ax,Ay) to (Bx,By).
* Let P be the point of perpendicular projection of C on AB. The parameter
* r, which indicates P's position along AB, is computed by the dot product
* of AC and AB divided by the square of the length of AB:
*
* (1) AC dot AB
* r = ---------
||AB||^2
*/
return(StartToEnd.Dot(v - Start) / LengthSquared);
}
/**
* Compare this line segment to another and return true if the lines are parallel.
*/
public bool IsParallel(LineSegment2D other, float tolerance = 0)
{
return(Math.Abs(StartToEnd.Cross(other.StartToEnd)) <= tolerance);
}