/// <summary>
/// This method can also be called to clear the object of any of its data from a previous run. You do this when you
/// want to create some blue noise. For instance with the Lloyd Relaxation iterations.
/// </summary>
/// <created>Dennis Steinmeijer</created>
/// <date>2013-07-20</date>
public void Reset()
{
this.SiteList.Clear();
this.Sites.Clear();
this.Cells.Clear();
this.FirstCircle = null;
this.Edges.Clear();
this.BeachLines = new RBTree();
this.Circles = new RBTree();
this.BeachJunkyard.Clear();
this.CircleJunkyard.Clear();
this.EdgeVertices.Clear();
}
/// <summary>
/// Checks to see if a circle event is available in the junkyard and uses it,
/// or makes a new one and returns it.
/// </summary>
private Circle GetCircle()
{
Circle objCircle = null;
// Check to see whether the stack is empty.
if (this.CircleJunkyard.Count > 0)
{
// Try to retrieve a circle vent from the junkyard.
objCircle = this.CircleJunkyard.Pop();
}
// If we don't find a circle event in the junkyard we'll make a new one.
if (objCircle == null)
{
objCircle = new Circle();
}
// And give it back!
return objCircle;
}
/// <summary>
/// Attach a circle event.
/// </summary>
private void AttachCircle(Beach objArc)
{
// This is a node in the RBTree which points to a beachsection.
Beach objArcLeft = objArc.Previous as Beach;
Beach objArcRight = objArc.Next as Beach;
if (objArcLeft == null || objArcRight == null)
{
return;
} // Does that ever happen?
Point objSiteLeft = objArcLeft.Site;
Point objSite = objArc.Site;
Point objSiteRight = objArcRight.Site;
// If site of left beachsection is same as site of right beachsection, there can't be convergence.
if (objSiteLeft == objSiteRight)
{
return;
}
// Find the circumscribed circle for the three sites associated
// with the beachsection triplet.
// rhill 2011-05-26: It is more efficient to calculate in-place
// rather than getting the resulting circumscribed circle from an
// object returned by calling Voronoi.circumcircle()
// http://mathforum.org/library/drmath/view/55002.html
// Except that I bring the origin at cSite to simplify calculations.
// The bottom-most part of the circumcircle is our Fortune 'circle
// event', and its center is a vertex potentially part of the final
// Voronoi diagram.
double bx = objSite.x;
double by = objSite.y;
double ax = objSiteLeft.x - bx;
double ay = objSiteLeft.y - by;
double cx = objSiteRight.x - bx;
double cy = objSiteRight.y - by;
// If points l->c->r are clockwise, then center beach section does not
// collapse, hence it can't end up as a vertex (we reuse 'd' here, which
// sign is reverse of the orientation, hence we reverse the test.
// http://en.wikipedia.org/wiki/Curve_orientation#Orientation_of_a_simple_polygon
// rhill 2011-05-21: Nasty finite precision error which caused circumcircle() to
// return infinites: 1e-12 seems to fix the problem.
double d = 2 * (ax * cy - ay * cx);
if (d >= -2e-12)
{
return;
}
double ha = ax * ax + ay * ay;
double hc = cx * cx + cy * cy;
double x = (cy * ha - ay * hc) / d;
double y = (ax * hc - cx * ha) / d;
double ycenter = y + by;
// Important: ybottom should always be under or at sweep, so no need
// to waste CPU cycles by checking
// Recycle circle event object if possible.
Circle objCircle = this.GetCircle();
objCircle.Arc = objArc;
objCircle.Site = objSite;
objCircle.x = x + bx;
objCircle.y = ycenter + Math.Sqrt(x * x + y * y); // y bottom
objCircle.ycenter = ycenter;
objArc.Circle = objCircle;
// find insertion point in RB-tree: circle events are ordered from
// smallest to largest
Circle objNodePrevious = null;
Circle objNode = this.Circles.Root as Circle;
while (objNode != null)
{
if (objCircle.y < objNode.y || (objCircle.y == objNode.y && objCircle.x <= objNode.x))
{
if (objNode.Left != null)
{
objNode = objNode.Left as Circle;
}
else
{
objNodePrevious = objNode.Previous as Circle;
break;
}
}
else
{
if (objNode.Right != null)
{
objNode = objNode.Right as Circle;
}
else
{
objNodePrevious = objNode;
break;
}
}
}
this.Circles.InsertSuccessor(objNodePrevious, objCircle);
if (objNodePrevious == null)
{
this.FirstCircle = objCircle;
}
}
/// <summary>
/// Detach a circle event.
/// </summary>
private void DetachCircleEvent(Beach objArc)
{
Circle objCircle = objArc.Circle;
if (objCircle == null)
{
return;
}
if (objCircle.Previous == null)
{
this.FirstCircle = objCircle.Next as Circle;
}
// Remove from RBTree.
this.Circles.RemoveNode(objCircle);
this.CircleJunkyard.Push(objCircle);
objArc.Circle = null;
}
