/// <summary>
/// Case 2: edge origin lies outside the domain.
/// </summary>
private void HandleCase2(HalfEdge edge, TVertex v1, TVertex v2)
{
// The vertices of the infinite edge.
var p1 = (Point)edge.origin;
var p2 = (Point)edge.twin.origin;
// The two edges leaving p1, pointing into the mesh.
var e1 = edge.twin.next;
var e2 = e1.twin.next;
// Find the two intersections with boundary edge.
IntersectionHelper.IntersectSegments(v1, v2, e1.origin, e1.twin.origin, ref p2);
IntersectionHelper.IntersectSegments(v1, v2, e2.origin, e2.twin.origin, ref p1);
// The infinite edge will now lie on the boundary. Update pointers:
e1.twin.next = edge.twin;
edge.twin.next = e2;
edge.twin.face = e2.face;
e1.origin = edge.twin.origin;
edge.twin.twin = null;
edge.twin = null;
// Close the cell.
var gen = factory.CreateVertex(v1.x, v1.y);
var he = factory.CreateHalfEdge(gen, edge.face);
edge.next = he;
he.next = edge.face.edge;
// Let the face edge point to the edge leaving at generator.
edge.face.edge = he;
base.edges.Add(he);
he.id = base.edges.Count;
gen.id = offset++;
base.vertices.Add(gen);
}
/// <summary>
/// Case 1: edge origin lies inside the domain.
/// </summary>
private void HandleCase1(HalfEdge edge, TVertex v1, TVertex v2)
{
//int mark = GetBoundaryMark(v1);
// The infinite vertex.
var v = (Point)edge.twin.origin;
// The half-edge is the bisector of v1 and v2, so the projection onto the
// boundary segment is actually its midpoint.
v.x = (v1.x + v2.x) / 2.0;
v.y = (v1.y + v2.y) / 2.0;
// Close the cell connected to edge.
var gen = factory.CreateVertex(v1.x, v1.y);
var h1 = factory.CreateHalfEdge(edge.twin.origin, edge.face);
var h2 = factory.CreateHalfEdge(gen, edge.face);
edge.next = h1;
h1.next = h2;
h2.next = edge.face.edge;
gen.leaving = h2;
// Let the face edge point to the edge leaving at generator.
edge.face.edge = h2;
base.edges.Add(h1);
base.edges.Add(h2);
int count = base.edges.Count;
h1.id = count;
h2.id = count + 1;
gen.id = offset++;
base.vertices.Add(gen);
}