/*
* The chordal axis is obtained by connecting the midpoints of the internal edges.
*/
protected Chord2D GetChordalAxis(Face2D external, List <Face2D> faces)
{
var t = external.Triangle;
Vertex2D src, dst;
Segment2D dstEdge;
bool e0 = ExternalSegment(t.s0);
bool e1 = ExternalSegment(t.s1);
bool e2 = ExternalSegment(t.s2);
if (e0 && e1)
{
src = t.s0.HasPoint(t.s1.a) ? t.s1.a : t.s1.b;
dst = triangulation.CheckAndAddVertex(t.s2.Midpoint());
dstEdge = t.s2;
}
else if (e1 && e2)
{
src = t.s1.HasPoint(t.s2.a) ? t.s2.a : t.s2.b;
dst = triangulation.CheckAndAddVertex(t.s0.Midpoint());
dstEdge = t.s0;
}
else
{
src = t.s2.HasPoint(t.s0.a) ? t.s0.a : t.s0.b;
dst = triangulation.CheckAndAddVertex(t.s1.Midpoint());
dstEdge = t.s1;
}
var chord = new Chord2D(src, dst, external);
chord.SetDstEdge(dstEdge);
var connection = new Connection2D(faces);
ChordalAxisRoutine(chord, connection);
return(chord);
}
protected void ChordalAxisRoutine(Chord2D chord, Connection2D connection)
{
var origin = chord.Face;
var neighbors = connection.GetNeighbors(origin);
connection.Remove(origin); // prevent overlaping to traverse
neighbors.ForEach(neighbor => {
var face = neighbor.face;
var segment = neighbor.joint;
Vertex2D destination;
Segment2D destinationEdge = null;
switch (face.Type)
{
case Face2DType.Junction:
destination = triangulation.CheckAndAddVertex(face.Centroid());
break;
case Face2DType.Sleeve:
var others = face.Triangle.ExcludeSegment(segment);
if (!ExternalSegment(others[0]))
{
destination = triangulation.CheckAndAddVertex(others[0].Midpoint());
destinationEdge = others[0];
}
else
{
destination = triangulation.CheckAndAddVertex(others[1].Midpoint());
destinationEdge = others[1];
}
break;
// case Face2DType.Terminal:
default:
destination = face.GetUncommonPoint(origin);
break;
}
Chord2D nextChord;
if (origin.Type == Face2DType.Junction)
{
var interval = new Chord2D(chord.Dst, triangulation.CheckAndAddVertex(segment.Midpoint()), origin);
interval.SetSrcEdge(chord.DstEdge); // maybe null
interval.SetDstEdge(segment);
nextChord = new Chord2D(interval.Dst, destination, face);
nextChord.SetSrcEdge(segment);
nextChord.SetDstEdge(destinationEdge); // null or exist
chord.Connect(interval);
interval.Connect(nextChord);
}
else
{
nextChord = new Chord2D(chord.Dst, destination, face);
nextChord.SetSrcEdge(chord.DstEdge);
nextChord.SetDstEdge(destinationEdge); // null or exist
chord.Connect(nextChord);
}
ChordalAxisRoutine(nextChord, connection);
});
}
