/// <summary>
/// Gets the arc on the beach line at the x coordinate (i.e. right above the new site event)
/// </summary>
/// <param name="p"></param>
/// <returns></returns>
private JCVHalfEdge GetEdgeAboveX(PointF p)
{
//guess that it's close by to last insert
JCVHalfEdge he = lastInserted;
if (he == null)
{
//changed to add "+ Bounds.Right"; believe original expression was erroneous
he = (p.X < Bounds.Width / 2 + Bounds.Right) ? beachlineStart : beachlineEnd;
}
//note: could be optimized with binary search
//then search right or left (as appropriate) until found
if (he == beachlineStart || (he != beachlineEnd && RightOf(he, p)))
{
do
{
he = he.right;
}while (he != beachlineEnd && RightOf(he, p));
he = he.left;
}
else
{
do
{
he = he.left;
}while (he != beachlineStart && !RightOf(he, p));
}
return(he);
}
private void SiteEvent(JCVSite site)
{
JCVHalfEdge left = GetEdgeAboveX(site.center);
JCVHalfEdge right = left.right;
JCVSite bottom = (left.Edge is null) ? sites[0] : left.rSite;
JCVEdge edge = new JCVEdge(bottom, site);
edges.Add(edge);
JCVHalfEdge he1 = new JCVHalfEdge(edge, false, left);
JCVHalfEdge he2 = new JCVHalfEdge(edge, true, he1);
lastInserted = right;
PointF p;
if (CheckCircleEvent(left, he1, out p))
{
priorityQueue.Remove(left);
left.vertex = p;
left.Y = p.Y + PointDistance(site.center, p);
priorityQueue.Add(left);
}
if (CheckCircleEvent(he2, right, out p))
{
he2.vertex = p;
he2.Y = p.Y + PointDistance(site.center, p);
priorityQueue.Add(he2);
}
}
//note to self: this is currently a black box. Figure out how it works at some point
private bool RightOf(JCVHalfEdge he, PointF p)
{
JCVEdge edge = he.Edge;
JCVSite topsite = edge.Sites[1];
bool rightOfSite = (p.X > topsite.X);
if (rightOfSite ^ he.directionIsRight) //direction and rightOfSite don't match
{
return(rightOfSite);
}
float dxp, dyp, dxs, t1, t2, t3, yl;
bool above;
if (edge.A == 1)
{
dyp = p.Y - topsite.Y;
dxp = p.X - topsite.X;
bool fast = false;
if ((!rightOfSite & (edge.B < 0)) || (rightOfSite & (edge.B >= 0)))
{
above = dyp >= edge.B * dxp;
fast = above;
}
else
{
above = (p.X + p.Y * edge.B) > edge.C;
if (edge.B < 0)
{
above = !above;
}
if (!above)
{
fast = true;
}
}
if (!fast)
{
dxs = topsite.X - edge.Sites[0].X;
above = edge.B * (dxp * dxp - dyp * dyp)
< dxs * dyp * (1 + 2 * dxp / dxs + edge.B * edge.B);
if (edge.B < 0)
{
above = !above;
}
}
}
else // edge.b == 1
{
yl = edge.C - edge.A * p.X;
t1 = p.Y - yl;
t2 = p.X - topsite.X;
t3 = yl - topsite.Y;
above = t1 * t1 > (t2 * t2 + t3 * t3);
}
return(he.directionIsRight ^ above);
}
private void CircleEvent()
{
JCVHalfEdge left = priorityQueue.First();
priorityQueue.Remove(left);
JCVHalfEdge leftleft = left.left;
JCVHalfEdge right = left.right;
JCVHalfEdge rightright = right.right;
JCVSite bottom = left.lSite;
JCVSite top = right.rSite;
PointF vertex = left.vertex;
EndPoints(left.Edge, vertex, left.directionIsRight);
EndPoints(right.Edge, vertex, right.directionIsRight);
lastInserted = rightright;
priorityQueue.Remove(right);
left.Unlink();
right.Unlink();
bool dirIsRight = false;
if (bottom.Y > top.Y)
{
JCVSite temp = bottom;
bottom = top;
top = temp;
dirIsRight = true;
}
JCVEdge edge = new JCVEdge(bottom, top);
edges.Add(edge);
JCVHalfEdge he = new JCVHalfEdge(edge, dirIsRight, leftleft);
EndPoints(edge, vertex, !dirIsRight);
PointF p;
if (CheckCircleEvent(leftleft, he, out p))
{
priorityQueue.Remove(leftleft);
leftleft.vertex = p;
leftleft.Y = p.Y + PointDistance(bottom.center, p);
priorityQueue.Add(leftleft);
}
if (CheckCircleEvent(he, rightright, out p))
{
he.vertex = p;
he.Y = p.Y + PointDistance(bottom.center, p);
priorityQueue.Add(he);
}
}
private bool CheckCircleEvent(JCVHalfEdge he1, JCVHalfEdge he2, out PointF vertex)
{
JCVEdge e1 = he1.Edge;
JCVEdge e2 = he2.Edge;
vertex = new PointF();
if (e1 is null || e2 is null || e1.Sites[1] == e2.Sites[1])
{
return(false);
}
return(HalfEdgeIntersection(he1, he2, out vertex));
}
private bool HalfEdgeIntersection(JCVHalfEdge he1, JCVHalfEdge he2, out PointF intersect)
{
JCVEdge e1 = he1.Edge;
JCVEdge e2 = he2.Edge;
intersect = new PointF();
float d = e1.A * e2.B - e1.B * e2.A; //determinant
if (-EDGE_INTERSECT_THRESHOLD < d && d < EDGE_INTERSECT_THRESHOLD) // lines are parallel
{
return(false);
}
float xint = (e1.C * e2.B - e1.B * e2.C) / d;
float yint = (e1.A * e2.C - e1.C * e2.A) / d;
intersect = new PointF(xint, yint);
JCVEdge e;
JCVHalfEdge he;
if (IsPointBefore(e1.Sites[1].center, e2.Sites[1].center))
{
he = he1;
e = e1;
}
else
{
he = he2;
e = e2;
}
bool rightOfSite = intersect.X >= e.Sites[1].X;
if (rightOfSite ^ he.directionIsRight)
{
return(false);
}
return(true);
}
/// <summary>
/// Generate the voronoi diagram.
/// </summary>
/// <param name="points"></param>
/// <param name="rect"></param>
/// <param name="clipper"></param>
public void GenerateDiagram(ref List <PointF> points, RectangleF rect, JCVClipper userClipper)
{
beachlineStart = new JCVHalfEdge(null, false);
beachlineEnd = new JCVHalfEdge(null, false);
clipper = userClipper;
priorityQueue = new SortedSet <JCVHalfEdge>();
beachlineStart.right = beachlineEnd;
beachlineEnd.left = beachlineStart;
lastInserted = null; //maybe not needed; added for clarity
edges = new List <JCVEdge>();
//create sites for each distinct point, sorted by min(y),min(x)
sites = points.Distinct().Select((p, index) => new JCVSite(p, index)).OrderBy(s => s.Y).ThenBy(s => s.X).ToList();
bool noRect = (rect == default);
if (noRect)
{
rect.X = sites.Min(s => s.X);
rect.Y = sites.Min(s => s.Y);
rect.Width = sites.Max(s => s.X) - rect.X;
rect.Height = sites.Max(s => s.Y) - rect.Y;
}
//uses clipper to clip any points outside bounds.
clipper.boundingBox = rect;
sites = (List <JCVSite>)sites.Where(s => clipper.TestPoint(s.center)).ToList();
if (noRect)
{
// JCash used ceil and floor to adjust the bounding box to int coords- necessary?
// see: jcv_rect_round(&tmp_rect);
// Will add later if needed
//pad bounding box by 10 in all directions
clipper.boundingBox.Inflate(10, 10);
rect = clipper.boundingBox;
}
this.Bounds = rect;
int siteIndex = 1; //sites[0] is saved for initial bottom site
int sCount = sites.Count;
bool finished = false;
while (!finished)
{
bool pqEmpty = (priorityQueue.Count == 0);
bool before = true;
if (!pqEmpty && siteIndex < sCount)
{
JCVHalfEdge he = priorityQueue.ElementAt(0);
PointF p = new PointF(he.vertex.X, he.Y);
before = IsPointBefore(sites[siteIndex].center, p);
}
if (siteIndex < sCount && (pqEmpty || before))
{
SiteEvent(sites[siteIndex++]);
}
else if (!pqEmpty)
{
CircleEvent();
}
else
{
finished = true;
}
} //end while
for (JCVHalfEdge temphe = beachlineStart.right; temphe != beachlineEnd; temphe = temphe.right)
{
FinishLine(temphe.Edge);
}
FillGaps();
}