/// <summary>
/// Return true if the vertex is reflex - that is if the angle between
/// its in-edge and out-edge is greater than Pi (180°) on the side of interest
/// </summary>
/// <param name="vertex">The vertex to be tested for reflexivity</param>
/// <returns>true if the vertex is reflex. false if the vertext is convex or straight.</returns>
private static bool IsReflex(Vertex vertex)
{
Edge inEdge = vertex.inEdge;
Edge outEdge = vertex.outEdge;
// TODO: Refactor to use Edge.Vector
Vector2D v1 = inEdge.target.Position - inEdge.source.Position;
Vector2D v2 = outEdge.target.Position - outEdge.source.Position;
double det = v1.Determinant(v2);
return(det > 0.0);
}
/// <summary>
/// Determine the direction bisecting the clockwise angle between vectors
/// a and b when vectors a and b are placed tip-to-tail.
/// </summary>
/// <param name="a">First vector</param>
/// <param name="b">Second vector</param>
/// <returns></returns>
public static Direction2D Bisector(ref Vector2D a, ref Vector2D b)
{
Vector2D aUnit = a.Unit;
Vector2D bUnit = b.Unit;
int sign = Math.Sign(a.Determinant(b));
if (sign < 0)
{
Direction2D bisector = new Direction2D(bUnit - aUnit);
return(bisector);
}
if (sign > 0)
{
Direction2D bisector = new Direction2D(aUnit - bUnit);
return(bisector);
}
// sign == 0 - vectors are parallel
if (Math.Sign(a.DeltaX) == Math.Sign(b.DeltaX) &&
Math.Sign(a.DeltaY) == Math.Sign(b.DeltaY))
{
return(new Direction2D(PerpendicularRight(a)));
}
return(new Direction2D(b));
}