public Line(Point origin, Point direction)
: this()
{
Origin = origin;
Direction = direction;
Normal = direction.Perp();
Ax = Normal.X;
By = Normal.Y;
C = Point.Dot(-PointAtDistance((Real)1.0), Normal);
}
public static int DetermineSide(Line line, Point normal, Point point)
{
Real value = Point.Dot(line.Normal, point) + line.C;
if (Math.Abs(value) < MathHelper.Epsilon)
{
return(0);
}
else if (value < 0)
{
return(-1);
}
else //if (value > 0)
{
return(1);
}
}
public static Line FromTwoPoints(Point point1, Point point2)
{
return(new Line(point1, point2 - point1));
}
public static int DetermineSide(Line line, Point point)
{
return(DetermineSide(line, line.Normal, point));
}
public Point PointAtDistance(Real distance)
{
return(Origin + distance * Point.Normalize(Direction));
}
/// <summary>
/// Returns a positive number if c is to the left of the line going from a to b.
/// </summary>
/// <returns>Positive number if point is left, negative if point is right,
/// and 0 if points are collinear.</returns>
public static double Area(ref Point a, ref Point b, ref Point c)
{
return(a.X * (b.Y - c.Y) + b.X * (c.Y - a.Y) + c.X * (a.Y - b.Y));
}
/// <summary>
/// Returns a positive number if c is to the left of the line going from a to b.
/// </summary>
/// <returns>Positive number if point is left, negative if point is right,
/// and 0 if points are collinear.</returns>
public static double Area(Point a, Point b, Point c)
{
return(Area(ref a, ref b, ref c));
}
public static bool Collinear(ref Point a, ref Point b, ref Point c, double tolerance)
{
return(MathHelper.DoubleInRange(Area(ref a, ref b, ref c), -tolerance, tolerance));
}
/// <summary>
/// Determines if three vertices are collinear (ie. on a straight line)
/// </summary>
/// <param name="a">First vertex</param>
/// <param name="b">Second vertex</param>
/// <param name="c">Third vertex</param>
/// <returns></returns>
public static bool Collinear(ref Point a, ref Point b, ref Point c)
{
return(Collinear(ref a, ref b, ref c, 0));
}
