/// <summary>
/// Connects two <see cref="QuadEdge"/> instances to the left of each other
/// </summary>
/// <param name="a">First instance to connect</param>
/// <param name="b">Second instance to connect</param>
/// <returns></returns>
public static QuadEdge ConnectLeft(QuadEdge a, QuadEdge b)
{
QuadEdge result = MakeEdge(a.Destination, b.Origin);
Splice(result, a.LeftNext);
Splice(result.Inverse, b);
return(result);
}
/// <summary>
/// Connects two <see cref="QuadEdge"/> instances to the right of each other
/// </summary>
/// <param name="a">First instance to connect</param>
/// <param name="b">Second instance to connect</param>
/// <returns></returns>
public static QuadEdge ConnectRight(QuadEdge a, QuadEdge b)
{
QuadEdge result = MakeEdge(a.Destination, b.Origin);
Splice(result, a.Inverse);
Splice(result.Inverse, b.OriginPrevious);
return(result);
}
/// <summary>
/// Splices two edges together
/// </summary>
/// <param name="a">First instance to splice</param>
/// <param name="b">Second instance to splice</param>
public static void Splice(QuadEdge a, QuadEdge b)
{
QuadEdge alpha = a.OriginNext.DualEdge;
QuadEdge beta = b.OriginNext.DualEdge;
QuadEdge temp = a.OriginNext;
QuadEdge temp2 = beta.OriginNext;
QuadEdge temp3 = alpha.OriginNext;
a.OriginNext = b.OriginNext;
b.OriginNext = temp;
alpha.OriginNext = temp2;
beta.OriginNext = temp3;
}
/// <summary>
/// Creates a QuadEdge instance from <paramref name="origin"/> to <paramref name="destination"/>
/// </summary>
/// <param name="origin"><see cref="Origin"/> of the <see cref="QuadEdge"/> to create</param>
/// <param name="destination"><see cref="Destination"/> of the <see cref="QuadEdge"/> to create</param>
/// <returns></returns>
public static QuadEdge MakeEdge(Point origin, Point destination)
{
//Create all quad edges
var q0 = new QuadEdge(origin);
var q1 = new QuadEdge(null);
var q2 = new QuadEdge(destination);
var q3 = new QuadEdge(null);
//Define links between edges
q0.OriginNext = q0;
q1.OriginNext = q3;
q2.OriginNext = q2;
q3.OriginNext = q1;
q0.DualEdge = q1;
q1.DualEdge = q2;
q2.DualEdge = q3;
q3.DualEdge = q0;
return(q0);
}
