public static HalfEdge[] FromTriangles(int[] triangles)
{
var index2vertex = new Dictionary<int, Vertex>();
var halfEdges = new List<HalfEdge>();
var vertex2halfEdges = new Dictionary<Vertex, LinkedList<HalfEdge>>();
for (var i = 0; i < triangles.Length; i+=3) {
var face = new Face();
var i0 = triangles[i];
var v0 = index2vertex.ContainsKey(i0) ? index2vertex[i0] : (index2vertex[i0] = new Vertex(){ index = i0 });
var he0 = new HalfEdge() { vertex = v0, face = face };
halfEdges.Add(he0);
v0.halfedge = he0;
var hedges0 = vertex2halfEdges.ContainsKey(v0) ? vertex2halfEdges[v0] : (vertex2halfEdges[v0] = new LinkedList<HalfEdge>());
hedges0.AddLast(he0);
var i1 = triangles[i+1];
var v1 = index2vertex.ContainsKey(i1) ? index2vertex[i1] : (index2vertex[i1] = new Vertex(){ index = i1 });
var he1 = new HalfEdge() { vertex = v1, face = face };
halfEdges.Add(he1);
v1.halfedge = he1;
var hedges1 = vertex2halfEdges.ContainsKey(v1) ? vertex2halfEdges[v1] : (vertex2halfEdges[v1] = new LinkedList<HalfEdge>());
hedges1.AddLast(he1);
var i2 = triangles[i+2];
var v2 = index2vertex.ContainsKey(i2) ? index2vertex[i2] : (index2vertex[i2] = new Vertex(){ index = i2 });
var he2 = new HalfEdge() { vertex = v2, face = face };
halfEdges.Add(he2);
v2.halfedge = he2;
var hedges2 = vertex2halfEdges.ContainsKey(v2) ? vertex2halfEdges[v2] : (vertex2halfEdges[v2] = new LinkedList<HalfEdge>());
hedges2.AddLast(he2);
face.halfedge = he0;
he0.next = he1;
he1.next = he2;
he2.next = he0;
}
foreach (var he in halfEdges) {
if (he.opposite != null)
continue;
var opposites = vertex2halfEdges[he.next.vertex];
foreach (var opposite in opposites) {
if (opposite.next.vertex == he.vertex) {
he.opposite = opposite;
opposite.opposite = he;
break;
}
}
}
return halfEdges.ToArray();
}
public void FlipEdge(HalfEdge he)
{
var f0 = he.face;
var f1 = he.opposite.face;
var he0a = he.next;
var he0b = he0a.next;
var he1 = he.opposite;
var he1a = he1.next;
var he1b = he1a.next;
he.vertex = he1b.vertex;
he1.vertex = he0b.vertex;
f0.halfedge = he0b;
he.face = he0b.face = he1a.face = f0;
f1.halfedge = he1b;
he1.face = he1b.face = he0a.face = f1;
he0b.next = he1a;
he1a.next = he;
he.next = he0b;
he1.next = he1b;
he1b.next = he0a;
he0a.next = he1;
_flipCheck.Push(he1a);
_flipCheck.Push(he1b);
}
public HalfEdge[] SplitTriangle(HalfEdge.Face f, Vector2 p)
{
faces.Remove(f);
var he = f.halfedge;
var f0 = new HalfEdge.Face(){ halfedge = he };
var f1 = new HalfEdge.Face(){ halfedge = he.next };
var f2 = new HalfEdge.Face(){ halfedge = he.next.next };
he.face = f0;
he.next.face = f1;
he.next.next.face = f2;
faces.Add(f0); faces.Add(f1); faces.Add(f2);
var v = new HalfEdge.Vertex(){ index = vertices.Count };
vertices.Add(p);
var he0a = new HalfEdge(){ vertex = v, next = he, face = f0 };
var he0b = new HalfEdge(){ vertex = he.next.vertex, next = he0a, face = f0 };
he = he.next;
he0a.next.next = he0b;
var he1a = new HalfEdge(){ vertex = v, next = he, face = f1 };
var he1b = new HalfEdge(){ vertex = he.next.vertex, next = he1a, face = f1 };
he = he.next;
he1a.next.next = he1b;
var he2a = new HalfEdge(){ vertex = v, next = he, face = f2 };
var he2b = new HalfEdge(){ vertex = he.next.vertex, next = he2a, face = f2 };
he = he.next;
he2a.next.next = he2b;
he0a.opposite = he2b; he2b.opposite = he0a;
he1a.opposite = he0b; he0b.opposite = he1a;
he2a.opposite = he1b; he1b.opposite = he2a;
halfEdges.AddRange(new HalfEdge[]{ he0a, he0b, he1a, he1b, he2a, he2b });
return new HalfEdge[]{ f0.halfedge, f1.halfedge, f2.halfedge };
}
