/// <summary>
/// A transition from one vertex to the next, where prev>id has the same direction as id>next
/// </summary>
/// <param name="id">the id of the current vertex</param>
/// <param name="prev">the id of previous polygon vertex</param>
/// <param name="next">the id of the next polygon vertex</param>
public void HandleTransition(IPolygonVertexInfo info)
{
var oldEdge = this.EdgeForVertex(info.Id, info.Unique);
var trapezoid = oldEdge.Trapezoid;
if (oldEdge.IsRightToLeft)
{
var newEdge = this.Transition(oldEdge, info.Prev, info.PrevUnique);
trapezoid.TransitionOnLowerEdge(info.Id, newEdge, this.splitSink);
}
else
{
var newEdge = this.Transition(oldEdge, info.Next, info.NextUnique);
trapezoid.TransitionOnUpperEdge(info.Id, newEdge, this.splitSink);
}
}
/// <summary>
/// Handle an opening cusp. i.e. starts two new edges.
/// </summary>
/// <param name="id">the id of the cusp vertex</param>
/// <param name="prev">the id of previous polygon vertex</param>
/// <param name="next">the id of the next polygon vertex</param>
public void HandleOpeningCusp(IPolygonVertexInfo info)
{
var(lowerEdge, upperEdge) = this.StartNewTrapezoidEdges(
info.Id,
info.Prev,
info.PrevUnique,
info.Next,
info.NextUnique);
if (lowerEdge.IsRightToLeft)
{
Trapezoid.EnterInsideBySplit(info.Id, lowerEdge, upperEdge);
}
else
{
var belowEdge = lowerEdge.TreeNode.Prev.Data;
var trapezoid = belowEdge.Trapezoid;
trapezoid.LeaveInsideBySplit(info.Id, lowerEdge, upperEdge, this.splitSink);
}
}
/// <summary>
/// Handle a closing cusp. i.e. joins two edges
/// </summary>
/// <param name="id">the id of the cusp vertex</param>
/// <param name="prev">the id of previous polygon vertex</param>
/// <param name="next">the id of the next polygon vertex</param>
public void HandleClosingCusp(IPolygonVertexInfo info)
{
var lowerEdge = this.EdgeForVertex(info.Id, info.Unique);
TrapezoidEdge upperEdge;
var prevEdge = lowerEdge.TreeNode.Prev?.Data;
if (prevEdge?.Right == lowerEdge.Right && (prevEdge.Left == info.Prev || prevEdge.Left == info.Next))
{
upperEdge = lowerEdge;
lowerEdge = prevEdge;
}
else
{
upperEdge = lowerEdge.TreeNode.Next?.Data;
}
if (lowerEdge.Right != upperEdge?.Right)
{
throw new InvalidOperationException($"Invalid join of edges lower: {lowerEdge} and upper: {upperEdge}");
}
var lowerTrapezoid = lowerEdge.Trapezoid;
if (lowerEdge.IsRightToLeft)
{
lowerTrapezoid.LeaveInsideByJoin(info.Id, this.splitSink);
}
else
{
var upperEdge2 = lowerEdge.TreeNode.Next.Data;
var upperTrapezoid = upperEdge2.Trapezoid;
Trapezoid.EnterInsideByJoin(lowerTrapezoid, upperTrapezoid, info.Id, this.splitSink);
}
this.JoinTrapezoidEdges(lowerEdge);
}