private TestCase SetupTripleArcTestCase(BreakpointNode leftBP, BreakpointNode rightBP, ArcNode leftArc,
ArcNode middleArc, ArcNode rightArc, ArcNode expectedResult, Vector newSitePos)
{
leftArc.Parent = leftBP;
middleArc.Parent = rightBP;
rightArc.Parent = rightBP;
leftBP.LeftChild = leftArc;
leftBP.RightChild = rightBP;
rightBP.Parent = leftBP;
rightBP.LeftChild = middleArc;
rightBP.RightChild = rightArc;
return new TestCase
{
RootNode = leftBP,
ExpectedResult = expectedResult,
NewSitePosition = newSitePos
};
}
public void FindsCorrectArcNode()
{
// First object is root node, second object is expected result arc node.
var tests = new List<TestCase>();
// A single arc.
{
var singleArc = new ArcNode(new Site(new Vector(0, 1)));
tests.Add(new TestCase
{
RootNode = singleArc,
ExpectedResult = singleArc,
NewSitePosition = new Vector(0, 0)
});
}
// Simple tree with three arcs.
{
/*
var leftArc = new ArcNode(new Site(new Vector(0, 10)));
var middleArc = new ArcNode(new Site(new Vector(5, 2)));
var rightArc = new ArcNode(leftArc.DefiningSite);
var leftBP = new BreakpointNode(leftArc.DefiningSite, middleArc.DefiningSite, null, true);
var rightBP = new BreakpointNode(leftArc.DefiningSite, middleArc.DefiningSite, null, false);
tests.Add(SetupTripleArcTestCase(
leftBP, rightBP, leftArc, middleArc, rightArc,
leftArc, new Vector(-5, 0)));
tests.Add(SetupTripleArcTestCase(
leftBP, rightBP, leftArc, middleArc, rightArc,
middleArc, new Vector(5, 0)));
tests.Add(SetupTripleArcTestCase(
leftBP, rightBP, leftArc, middleArc, rightArc,
rightArc, new Vector(500, 0)));
*/
}
// Three arc tree with sites vertically aligned.
{
// Breakpoints are at +- 7.01...
var leftArc = new ArcNode(new Site(new Vector(0, 10)));
var middleArc = new ArcNode(new Site(new Vector(0, 5)));
var rightArc = new ArcNode(leftArc.DefiningSite);
var leftBP = new BreakpointNode(leftArc.DefiningSite, middleArc.DefiningSite, null, true);
var rightBP = new BreakpointNode(leftArc.DefiningSite, middleArc.DefiningSite, null, false);
tests.Add(SetupTripleArcTestCase(
leftBP, rightBP, leftArc, middleArc, rightArc,
leftArc, new Vector(-250, 0)));
tests.Add(SetupTripleArcTestCase(
leftBP, rightBP, leftArc, middleArc, rightArc,
middleArc, new Vector(-1, 0)));
tests.Add(SetupTripleArcTestCase(
leftBP, rightBP, leftArc, middleArc, rightArc,
middleArc, new Vector(0, 0)));
tests.Add(SetupTripleArcTestCase(
leftBP, rightBP, leftArc, middleArc, rightArc,
middleArc, new Vector(1, 0)));
tests.Add(SetupTripleArcTestCase(
leftBP, rightBP, leftArc, middleArc, rightArc,
rightArc, new Vector(250, 0)));
}
foreach (var test in tests)
Assert.That(Helpers.FindArcSplitByNewSite(test.NewSitePosition, test.RootNode), Is.EqualTo(test.ExpectedResult));
}
private void HandleSiteEvent(SiteEvent ev, State state)
{
// If the beach line data structure is empty, initialize
// it with the arc created by the new site into it and return.
if (state.BeachLine == null)
{
state.BeachLine = new ArcNode(ev.Site);
return;
}
// Find the arc split by the new site.
var splitArcNode = Helpers.FindArcSplitByNewSite(ev.Site.Position, state.BeachLine);
// If the arc being split has a circle event, it is a false alarm,
// so delete it from the event queue.
if (splitArcNode.DisappearanceEvent != null)
state.EventQueue.Remove(splitArcNode.DisappearanceEvent.Index);
// The following pieces of the final Voronoi diagram are created
// during a site event:
// - The Face defined by the new site.
// - Both HalfEdges of the edge that will be traced out by the
// two new breakpoints.
var newFace = new Face {UserData = ev.Site.UserData};
var halfEdgeFacingOldSite = new HalfEdge();
var halfEdgeFacingNewSite = new HalfEdge();
state.Faces.Add(ev.Site, newFace);
state.HalfEdges.Add(halfEdgeFacingOldSite);
state.HalfEdges.Add(halfEdgeFacingNewSite);
// Link all the diagram pieces together that can be linked at this time.
halfEdgeFacingOldSite.Interior = state.Faces[splitArcNode.DefiningSite];
halfEdgeFacingNewSite.Interior = newFace;
halfEdgeFacingOldSite.Twin = halfEdgeFacingNewSite;
halfEdgeFacingNewSite.Twin = halfEdgeFacingOldSite;
// During a site event, an existing arc is split into two
// new arcs with an additional arc in the middle. We reflect
// this change in beach line status tree data structure by
// replacing the split arc node with a new subtree with five
// nodes total: two for the two new breakpoints, and three
// for the three new arcs on the beach line.
var leftBP = new BreakpointNode(ev.Site, splitArcNode.DefiningSite, halfEdgeFacingOldSite, true);
var rightBP = new BreakpointNode(ev.Site, splitArcNode.DefiningSite, halfEdgeFacingNewSite, false);
var leftArc = new ArcNode(splitArcNode.DefiningSite);
var middleArc = new ArcNode(ev.Site);
var rightArc = new ArcNode(splitArcNode.DefiningSite);
// Set up new subtree.
leftBP.LeftChild = leftArc;
leftBP.RightChild = rightBP;
rightBP.LeftChild = middleArc;
rightBP.RightChild = rightArc;
rightBP.Parent = leftBP;
leftArc.Parent = leftBP;
middleArc.Parent = rightBP;
rightArc.Parent = rightBP;
// Graft new subtree into existing beach line status tree data structure.
// First check for the special case where the split arc node was the
// root element of the tree (aka the only element).
if (splitArcNode.Parent == null)
{
if (state.BeachLine != splitArcNode)
throw new SanityCheckFailedException(
"The splitArcNode's parent was null, but it was not the root of the beach line status tree data structure.");
state.BeachLine = leftBP;
}
// Otherwise, graft into existing tree. Here is where
// we would perform rebalancing operations on the tree.
else
{
if (splitArcNode.Parent.LeftChild == splitArcNode)
{
splitArcNode.Parent.LeftChild = leftBP;
leftBP.Parent = splitArcNode.Parent;
}
else
{
splitArcNode.Parent.RightChild = leftBP;
leftBP.Parent = splitArcNode.Parent;
}
}
}