/* Function: deleteCircleEvent
* ---------------------------
* Deletes a potential circle event associated with a site event
* from the event queue (it is no longer correct).
*/
private void deleteCircleEvent(BeachArc arc)
{
CircleEvent ce = arc.circleEvent;
arc.circleEvent = null;
if (ce != null && sweepLine.Contains(ce))
{
sweepLine.Remove(ce);
usedCircleEvents.Add(ce);
}
}
/* Method: computeVoronoiDiagram
* -----------------------------
* Computes Fortune Voronoi digram and returns it.
*/
public VoronoiDiagram computeVoronoiDiagram()
{
int currSiteID = 0;
float lastEventX, lastEventY;
lastEventX = lastEventY = Mathf.Infinity;
Event e = null;
while (sweepLine.Count > 0)
{
e = sweepLine.Dequeue(); // remove event from queue with largest y-coord
if (e.isSiteEvent && !isDuplicate(e, lastEventX, lastEventY))
{
e.site.setId(currSiteID);
cells.Insert(e.site.id, new VoronoiCell(e.site)); // add new cell at id
// Add site to beach section
handleSiteEvent(e.site);
// Update for next event
currSiteID++;
lastEventX = e.site.x;
lastEventY = e.site.y;
}
else
{
CircleEvent ce = (CircleEvent)e;
handleCircleEvent(ce.arc);
}
}
// Terminate cell edges after queue empty on a bounding box (they go to infinite)
clipEdgesOnBounds();
closeCells();
// Build Voronoi diagram
VoronoiDiagram diagram = new VoronoiDiagram();
diagram.sites = sites;
diagram.cells = cells;
diagram.edges = edges;
reset();
return(diagram);
}
/* Function: getTripleArcCircleEvent
* ---------------------------------
* Checks sites of three arcs for convergence of breakpoints, i.e. beach will
* collapse giving rise to a circle event. If true, gets a circle event and
* updates its fields on the receiving arc and event queue.
*
* Note: Calculation of circle event based on Jeremie St-Amand's:
* https://github.com/jesta88/Unity-Voronoi/blob/master/Assets/Voronoi/FortuneVoronoi.cs
*/
private void getTripleArcCircleEvent(Site left, ref BeachArc center, Site right)
{
float cx = center.site.x;
float cy = center.site.y;
float lx = left.x - cx;
float ly = left.y - cy;
float rx = right.x - cx;
float ry = right.y - cy;
float orientation = 2 * (lx * ry - ly * rx);
// Points are CW, beach section does not collapse so no event
if (orientation >= -2e-12)
{
return;
}
float lLengthSquared = lx * lx + ly * ly;
float rLengthSquared = rx * rx + ry * ry;
float x = (ry * lLengthSquared - ly * rLengthSquared) / orientation;
float y = (lx * rLengthSquared - rx * lLengthSquared) / orientation;
float yCenter = y + cy; // at or below sweepline
// Get circle event to setup
CircleEvent circleEvent = null;
if (usedCircleEvents.Count > 0)
{
circleEvent = usedCircleEvents.Last();
usedCircleEvents.Remove(circleEvent);
}
else
{
circleEvent = new CircleEvent();
}
// Update fields
circleEvent.site = center.site;
circleEvent.arc = center;
circleEvent.setPosition(x + cx, yCenter + Mathf.Sqrt(x * x + y * y), yCenter);
center.circleEvent = circleEvent;
// Add to event queue
sweepLine.Enqueue(circleEvent, circleEvent);
}
/* Function: handleCircleEvent
* ---------------------------
* Handles circle event.
*/
private void handleCircleEvent(BeachArc arc)
{
CircleEvent circleEvent = arc.circleEvent;
Vertex center = new Vertex(circleEvent.x, circleEvent.yCircleCenter);
BeachArc prev = arc.Prev;
BeachArc next = arc.Next;
LinkedList <BeachArc> disappearingTransitions = new LinkedList <BeachArc>();
disappearingTransitions.AddLast(arc);
deleteBeachArc(arc);
// Handle collapse left
BeachArc leftArc = prev;
while (leftArc.circleEvent != null && Mathf.Abs(center.x - leftArc.circleEvent.x) < EPS &&
Mathf.Abs(center.y - leftArc.circleEvent.yCircleCenter) < EPS)
{
prev = leftArc.Prev;
disappearingTransitions.AddFirst(leftArc);
deleteBeachArc(leftArc);
leftArc = prev;
}
// New left arc not dissappearing, but used in edge updates
disappearingTransitions.AddFirst(leftArc);
deleteCircleEvent(leftArc);
// Hanlde collapse right
BeachArc rightArc = next;
while (rightArc.circleEvent != null && Mathf.Abs(center.x - rightArc.circleEvent.x) < EPS &&
Mathf.Abs(center.y - rightArc.circleEvent.yCircleCenter) < EPS)
{
next = rightArc.Next;
disappearingTransitions.AddLast(rightArc);
deleteBeachArc(rightArc);
rightArc = next;
}
// New right arc not dissappearing, but used in edge updates
disappearingTransitions.AddLast(rightArc);
deleteCircleEvent(rightArc);
// Link existing edges at start point
int nArcs = disappearingTransitions.Count;
for (int i = 1; i < nArcs; i++)
{
rightArc = disappearingTransitions.ElementAt(i);
leftArc = disappearingTransitions.ElementAt(i - 1);
rightArc.edge.setStartVertex(leftArc.site, rightArc.site, center);
}
// Create new edge between previously non-adjacent arcs
// New vertex defines end point relative to site on the left
leftArc = disappearingTransitions.ElementAt(0);
rightArc = disappearingTransitions.ElementAt(nArcs - 1);
rightArc.edge = createNewEdge(leftArc.site, rightArc.site, null, center);
// Update circle events for arcs
findPotentialCircleEvent(leftArc);
findPotentialCircleEvent(rightArc);
}