// remove a point from sorted sweep line
public int RemoveSweep(SegPoint sp, double x)
{
spYComparer.x = x;
int pos = items.BinarySearch(sp, spYComparer);
if (pos >= 0)
{
items.RemoveAt(pos);
}
return(pos);
}
/*/ remove a point sorted by x position
* public void Remove(SegPoint sp)
* {
* int pos = items.BinarySearch(sp);
* if (pos >= 0)
* items.RemoveAt(pos);
* }*/
// add a point sorted by intersection of all existing lines in the list with a vertical line positioned at x
public int AddSweep(SegPoint sp, double x)
{
spYComparer.x = x;
int pos = items.BinarySearch(sp, spYComparer);
if (pos < 0)
{
pos = ~pos;
items.Insert(pos, sp);
}
return(pos);
}
// add a point sorted by x position
public int Add(SegPoint sp)
{
int pos = items.BinarySearch(sp);
if (pos < 0)
{
pos = ~pos;
items.Insert(pos, sp);
sp.segpix = pos;
}
return(pos);
}
// a (hopefully) faster version of FindIntersections()
// based on article from: http://geomalgorithms.com/a09-_intersect-3.html
public void FindIntersectionsFast()
{
// 1. add endpoints sorted leftmost to rightmost
SegPointList segPoints = new SegPointList();
for (int i = 0; i < segments.Count; i++)
{
SegPoint sp1 = new SegPoint(segments[i], i, true);
SegPoint sp2 = new SegPoint(segments[i], i, false);
sp1.otherPoint = sp2;
sp2.otherPoint = sp1;
segPoints.Add(sp1);
segPoints.Add(sp2);
}
SegPointList sweepPoints = new SegPointList();
int segix = 0;
while (segix < segPoints.Count)
{
SegPoint sp = segPoints.items[segix];
if (sp.isLeft)
{
// add to sweep line and test intersections with upper and lower segments
int sp_pos = sweepPoints.AddSweep(sp);
if (sp_pos > 0)
{
TestIntersections(segPoints, sweepPoints, sp_pos - 1, sp_pos);
}
if (sp_pos < (sweepPoints.Count - 1))
{
TestIntersections(segPoints, sweepPoints, sp_pos, sp_pos + 1);
}
}
else
{
// remove segment from sweep file and test intersection of neighboring segments
int sp_pos = sweepPoints.RemoveSweep(sp.otherPoint);
if ((sp_pos > 0) && (sp_pos < sweepPoints.Count))
{
TestIntersections(segPoints, sweepPoints, sp_pos - 1, sp_pos);
}
}
segix++;
}
}
private void TestIntersections(SegPointList segPoints, SegPointList sweepPoints, int sp_pos1, int sp_pos2)
{
SegPoint sp1 = sweepPoints.items[sp_pos1];
SegPoint sp2 = sweepPoints.items[sp_pos2];
List <Segment2D> splits = sp1.seg.Intersect(sp2.seg, this);
if (splits != null)
{
// splits must be >= 2
foreach (Segment2D seg in splits)
{
SegPoint nspL = new SegPoint(seg, 0, true);
SegPoint nspR = new SegPoint(seg, 0, false);
nspR.otherPoint = nspL;
nspL.otherPoint = nspR;
if (Object.ReferenceEquals(nspL.pt, sp1.pt))
{
// matches begining of sp1, replace sp1 with new segment in all places
nspL.segix = sp1.segix;
nspL.segpix = sp1.segpix;
segPoints.items[nspL.segpix] = nspL;
segments[nspL.segix] = seg;
sweepPoints.items[sp_pos1] = nspL;
}
else if (Object.ReferenceEquals(nspL.pt, sp2.pt))
{
// matches begining of sp2, replace sp2 with new segment in all places
nspL.segix = sp2.segix;
nspL.segpix = sp2.segpix;
segPoints.items[nspL.segpix] = nspL;
segments[nspL.segix] = seg;
sweepPoints.items[sp_pos2] = nspL;
}
else
{
// new segment, add everywhere
nspL.segix = segments.Count;
segments.Add(seg);
segPoints.Add(nspL);
}
nspR.segix = nspL.segix;
if (Object.ReferenceEquals(nspR.pt, sp1.otherPoint.pt))
{
// matches ending of sp1, replace sp1 endings in all places
nspR.segpix = sp1.otherPoint.segpix;
segPoints.items[nspR.segpix] = nspR;
//sweepPoints.items[sp_pos1] = nspL;
}
else if (Object.ReferenceEquals(nspR.pt, sp2.otherPoint.pt))
{
// matches ending of sp2, replace sp2 endings in all places
nspR.segpix = sp2.otherPoint.segpix;
segPoints.items[nspR.segpix] = nspR;
//sweepPoints.items[sp_pos2] = nspL;
}
else
{
// new segment point, add to segment points
segPoints.Add(nspR);
}
}
}
}
public int RemoveSweep(SegPoint sp)
{
return(RemoveSweep(sp, sp.pt.x));
}
public int AddSweep(SegPoint sp)
{
return(AddSweep(sp, sp.pt.x));
}