/// <summary>
/// Determines the shortest distance from this point to the specified line segment.
/// </summary>
/// <param name="line">The line segment.</param>
/// <param name="sign">-1 if the point resides above the line, or 1 if the point resides below the line.</param>
/// <returns></returns>
public double DistanceTo(LineSeg2D line, out int sign)
{
double dist = CrossProduct(line.Start, line.End, this) / Delta(line.Start, line.End);
if (dist < 0)
{
sign = -1;
}
else
{
sign = 1;
}
return(Math.Abs(dist));
}
/// <summary>
/// Determines the point of intersection between the specified lines.
/// </summary>
/// <param name="line1">Line 1.</param>
/// <param name="line2">Line 2.</param>
/// <returns>The point of intersection if the lines intersect; otherwise, null.</returns>
public static Point2D IntersectAt(LineSeg2D line1, LineSeg2D line2)
{
// Denominator for ua and ub are the same, so store this calculation
double d =
(line2.Y2 - line2.Y1) * (line1.X2 - line1.X1)
-
(line2.X2 - line2.X1) * (line1.Y2 - line1.Y1);
//n_a and n_b are calculated as seperate values for readability
double n_a =
(line2.X2 - line2.X1) * (line1.Y1 - line2.Y1)
-
(line2.Y2 - line2.Y1) * (line1.X1 - line2.X1);
double n_b =
(line1.X2 - line1.X1) * (line1.Y1 - line2.Y1)
-
(line1.Y2 - line1.Y1) * (line1.X1 - line2.X1);
// Make sure there is not a division by zero - this also indicates that
// the lines are parallel.
if (d == 0)
{
return(null);
}
// Calculate the intermediate fractional point that the lines potentially intersect.
double ua = n_a / d;
double ub = n_b / d;
Point2D intersection = null;
if (ua >= 0d && ua <= 1d && ub >= 0d && ub <= 1d)
{
intersection = new Point2D();
intersection.X = line1.X1 + (ua * (line1.X2 - line1.X1));
intersection.Y = line1.Y1 + (ua * (line1.Y2 - line1.Y1));
}
return(intersection);
}
/// <summary>
/// Determines the angle between line 1 and line 2.
/// </summary>
/// <param name="line1">Line 1.</param>
/// <param name="line2">Line 2.</param>
/// <returns></returns>
public static double AngleBetween(LineSeg2D line1, LineSeg2D line2)
{
return(System.Math.Atan2(line1.Y2 - line1.Y1, line1.X2 - line1.X1) - System.Math.Atan2(line2.Y2 - line2.Y1, line2.X2 - line2.X1));
}
/// <summary>
/// Determines the shortest distance from this point to the specified line segment.
/// </summary>
/// <param name="line">The line segment.</param>
/// <returns></returns>
public double DistanceTo(LineSeg2D line)
{
double dist = CrossProduct(line.Start, line.End, this) / Delta(line.Start, line.End);
return(Math.Abs(dist));
}
