/// <summary>
/// Sort the half edges.
/// </summary>
private int SortHalfEdges(HalfEdge a, HalfEdge b)
{
double r = b.Angle - a.Angle;
if (r < 0) { return -1; }
if (r > 0) { return 1; }
return 0;
}
/// <summary>
/// Close cells.
/// </summary>
private void CloseCells()
{
// Prune and order the halfedges, then add missing halfedges in order to close the cells.
for (int intCell = this.Cells.Count; intCell > 0; intCell--)
{
// Grab the cell object.
Cell objCell = this.Cells[intCell];
// Prepare the cell by pruning and ordering the halfedges.
objCell.PrepareHalfEdges();
// close open cells
// step 1: find first 'unclosed' point, if any.
// an 'unclosed' point will be the end point of a halfedge which
// does not match the start point of the following halfedge
int intHalfEdges = objCell.HalfEdges.Count;
int intLeft = 0;
while (intLeft < intHalfEdges)
{
int intRight = (intLeft + 1) % intHalfEdges;
Point objEnd = objCell.HalfEdges[intLeft].GetEndPoint();
Point objStart = objCell.HalfEdges[intRight].GetStartPoint();
// if end point is not equal to start point, we need to add the missing halfedge(s) to close the cell
if ((Math.Abs(objEnd.x - objStart.x) >= Polygons.Epsilon || Math.Abs(objEnd.y - objStart.y) >= Polygons.Epsilon))
{
// if we reach this point, cell needs to be closed by walking counterclockwise along the bounding box until it connects to next halfedge in the list
Point objVertexA = objEnd;
double x;
double y;
Point objVertexB = null;
// walk downward along left side
if (this.EqualWithEpsilon(objEnd.x, this.Box.xl) && this.LessThanWithEpsilon(objEnd.y, this.Box.yb))
{
x = this.Box.xl;
y = this.EqualWithEpsilon(objStart.x, this.Box.xl) ? objStart.y : this.Box.yb;
objVertexB = this.CreateEdgeVertex(x, y);
}
// walk rightward along bottom side
else if (this.EqualWithEpsilon(objEnd.y, this.Box.yb) && this.LessThanWithEpsilon(objEnd.x, this.Box.xr))
{
x = this.EqualWithEpsilon(objStart.y, this.Box.yb) ? objStart.x : this.Box.xr;
y = this.Box.yb;
objVertexB = this.CreateEdgeVertex(x, y);
}
// walk upward along right side
else if (this.EqualWithEpsilon(objEnd.x, this.Box.xr) && this.GreaterThanWithEpsilon(objEnd.y, this.Box.yt))
{
x = this.Box.xr;
y = this.EqualWithEpsilon(objStart.x, this.Box.xr) ? objStart.y : this.Box.yt;
objVertexB = this.CreateEdgeVertex(x, y);
}
// walk leftward along top side
else if (this.EqualWithEpsilon(objEnd.y, this.Box.yt) && this.GreaterThanWithEpsilon(objEnd.x, this.Box.xl))
{
x = this.EqualWithEpsilon(objStart.y, this.Box.yt) ? objStart.x : this.Box.xl;
y = this.Box.yt;
objVertexB = this.CreateEdgeVertex(x, y);
}
// Create a new half edge.
HalfEdge objHalfEdge = new HalfEdge(this.CreateBorderEdge(objCell.Site, objVertexA, objVertexB), objCell.Site, null);
objCell.HalfEdges.Insert(intLeft + 1, objHalfEdge);
intHalfEdges = objCell.HalfEdges.Count;
}
if (intLeft > 100)
{
// Clearly something is going awfully wrong. What site is causing this problem?
throw new Exception("CloseCells: Trouble with seed " + this.Seed + ". Site (" + objCell.Site.ID.ToString() + ") " + objCell.Site.ToString() + ".");
}
intLeft++;
}
}
}
