/// <summary>
/// Attempt to generate the Delaunay triangulation for this graph.
/// Returns null on success. Otherwise returns the node which could not
/// be traingulated.
/// </summary>
/// <returns></returns>
private EuclideanGraphNode <T> AttemptDelaunayTriangulation()
{
// Create convex hull which spans the data
EuclideanGraphNode <T> anchor1 = new EuclideanGraphNode <T>(new Vector2(0f, 2f * Radius));
EuclideanGraphNode <T> anchor2 = new EuclideanGraphNode <T>(new Vector2(Mathf.Sqrt(3f) * Radius, -Radius));
EuclideanGraphNode <T> anchor3 = new EuclideanGraphNode <T>(new Vector2(-Mathf.Sqrt(3f) * Radius, -Radius));
DelaunayTree.DelaunayTree <T> tree = new DelaunayTree.DelaunayTree <T>(new EuclideanGraphTriangle <T>(anchor1, anchor2, anchor3));
int nodesInserted = 0;
// Insert one node at a time, always updating the delaunay triangulation
foreach (EuclideanGraphNode <T> node in Nodes)
{
ProgressTracker.Instance.PushActivity("Inserting node " + (nodesInserted++).ToString() + "/" + Nodes.Count.ToString());
EuclideanGraphTriangle <T> entryTriangle = tree.GetTriangle(node.GetPosition());
if (entryTriangle == null)
{
ProgressTracker.Instance.PopActivity();
return(node);
}
EuclideanGraphTriangle <T>[] subdivisions = entryTriangle.Subdivide(node);
tree.Subdivide(entryTriangle, subdivisions);
Queue <EuclideanGraphNode <T>[]> edgesToVerify = entryTriangle.GetEdges();
while (edgesToVerify.Count > 0)
{
VerifyNextEdge(tree, edgesToVerify);
}
ProgressTracker.Instance.PopActivity();
}
ProgressTracker.Instance.PushActivity("Gathering edges");
// Transfer to edge data structure
List <EuclideanGraphTriangle <T> > triangles = tree.GetCurrentTriangles();
foreach (EuclideanGraphTriangle <T> triangle in triangles)
{
Queue <EuclideanGraphNode <T>[]> edges = triangle.GetEdges();
foreach (EuclideanGraphNode <T>[] edge in edges)
{
if (edge[0].HasData && edge[1].HasData)
{
AddEdge(edge[0], edge[1]);
}
}
}
ProgressTracker.Instance.PopActivity();
return(null);
}
private void VerifyNextEdge(DelaunayTree.DelaunayTree <T> delaunayTree, Queue <EuclideanGraphNode <T>[]> edgesToVerify)
{
EuclideanGraphNode <T>[] edge = edgesToVerify.Dequeue();
EuclideanGraphTriangle <T> triangle1 = null;
EuclideanGraphTriangle <T> triangle2 = null;
delaunayTree.GetTrianglesOnEdge(edge, ref triangle1, ref triangle2);
//There is only one triangle on an edge between anchor points (which cannot be flipped)
if (triangle2 == null)
{
return;
}
float alpha = triangle1.GetOppositeAngle(edge);
float beta = triangle2.GetOppositeAngle(edge);
// If the sum of opposite angles is > 180 we need to flip
if (alpha + beta > 180f)
{
// Enqueue other edges which may need to be flipped as a result of this flip
EuclideanGraphNode <T>[][] otherEdges = triangle1.GetOtherEdges(edge);
edgesToVerify.Enqueue(otherEdges[0]);
edgesToVerify.Enqueue(otherEdges[1]);
otherEdges = triangle2.GetOtherEdges(edge);
edgesToVerify.Enqueue(otherEdges[0]);
edgesToVerify.Enqueue(otherEdges[1]);
// Create two new triangles
EuclideanGraphNode <T> corner1 = triangle1.GetOppositeCorner(edge);
EuclideanGraphNode <T> corner2 = triangle2.GetOppositeCorner(edge);
EuclideanGraphTriangle <T> newTriangle1 = new EuclideanGraphTriangle <T>(corner1, corner2, edge[0]);
EuclideanGraphTriangle <T> newTriangle2 = new EuclideanGraphTriangle <T>(corner1, corner2, edge[1]);
// Update the Delaunay Tree
delaunayTree.Replace(triangle1, triangle2, newTriangle1, newTriangle2);
}
}
