Polygon ComputeInternal(PolygonOp operation)
{
Polygon result = null;
sortedEvents = new List <SweepEvent>();
// Init event queue
eventQueue = new EventQueue();
// Test 1 for trivial result case
if (subject.contours.Count * clipping.contours.Count == 0)
{
if (operation == PolygonOp.DIFFERENCE)
{
result = subject;
}
else if (operation == PolygonOp.UNION || operation == PolygonOp.XOR)
{
result = (subject.contours.Count == 0) ? clipping : subject;
}
return(result);
}
// Test 2 for trivial result case
Rectangle subjectBB = subject.boundingBox;
Rectangle clippingBB = clipping.boundingBox;
if (!subjectBB.Intersects(clippingBB))
{
if (operation == PolygonOp.DIFFERENCE)
{
result = subject;
}
if (operation == PolygonOp.UNION || operation == PolygonOp.XOR)
{
result = subject;
foreach (Contour c in clipping.contours)
{
result.AddContour(c);
}
}
return(result);
}
// Add each segment to the eventQueue, sorted from left to right.
for (int k = 0; k < subject.contours.Count; k++)
{
Contour sCont = subject.contours[k];
for (int pParse1 = 0; pParse1 < sCont.points.Count; pParse1++)
{
ProcessSegment(sCont.GetSegment(pParse1), PolygonType.SUBJECT);
}
}
for (int k = 0; k < clipping.contours.Count; k++)
{
Contour cCont = clipping.contours[k];
for (int pParse2 = 0; pParse2 < cCont.points.Count; pParse2++)
{
ProcessSegment(cCont.GetSegment(pParse2), PolygonType.CLIPPING);
}
}
Connector connector = new Connector();
// This is the SweepLine. That is, we go through all the polygon edges
// by sweeping from left to right.
SweepEventSet S = new SweepEventSet();
double MINMAX_X = Math.Min(subjectBB.right, clippingBB.right) + Point.PRECISION;
SweepEvent prev, next;
int panicCounter = 0; // This is a safety check to prevent infinite loops (very rare but could happen due to floating-point issues with a high number of points)
while (!eventQueue.isEmpty)
{
if (panicCounter++ > 50000)
{
Debug.Log("PANIC!");
break;
}
prev = null;
next = null;
SweepEvent e = eventQueue.Dequeue();
if ((operation == PolygonOp.INTERSECTION && e.p.x > MINMAX_X) || (operation == PolygonOp.DIFFERENCE && e.p.x > subjectBB.right + Point.PRECISION))
{
return(connector.ToPolygonFromLargestLineStrip());
}
if (operation == PolygonOp.UNION && e.p.x > MINMAX_X)
{
// add all the non-processed line segments to the result
if (!e.isLeft)
{
connector.Add(e.segment);
}
while (!eventQueue.isEmpty)
{
e = eventQueue.Dequeue();
if (!e.isLeft)
{
connector.Add(e.segment);
}
}
return(connector.ToPolygonFromLargestLineStrip());
}
if (e.isLeft) // the line segment must be inserted into S
{
int pos = S.Insert(e);
prev = (pos > 0) ? S.eventSet[pos - 1] : null;
next = (pos < S.eventSet.Count - 1) ? S.eventSet[pos + 1] : null;
if (prev == null)
{
e.inside = e.inOut = false;
}
else if (prev.edgeType != EdgeType.NORMAL)
{
if (pos - 2 < 0) // e overlaps with prev
// Not sure how to handle the case when pos - 2 < 0, but judging
// from the C++ implementation this looks like how it should be handled.
{
e.inside = e.inOut = false;
if (prev.polygonType != e.polygonType)
{
e.inside = true;
}
else
{
e.inOut = true;
}
}
else
{
SweepEvent prevTwo = S.eventSet[pos - 2];
if (prev.polygonType == e.polygonType)
{
e.inOut = !prev.inOut;
e.inside = !prevTwo.inOut;
}
else
{
e.inOut = !prevTwo.inOut;
e.inside = !prev.inOut;
}
}
}
else if (e.polygonType == prev.polygonType)
{
e.inside = prev.inside;
e.inOut = !prev.inOut;
}
else
{
e.inside = !prev.inOut;
e.inOut = prev.inside;
}
// Process a possible intersection between "e" and its next neighbor in S
if (next != null)
{
PossibleIntersection(e, next);
}
// Process a possible intersection between "e" and its previous neighbor in S
if (prev != null)
{
PossibleIntersection(prev, e);
}
}
else // the line segment must be removed from S
// Get the next and previous line segments to "e" in S
{
int otherPos = -1;
for (int evt = 0; evt < S.eventSet.Count; evt++)
{
if (e.otherSE.Equals(S.eventSet[evt]))
{
otherPos = evt;
break;
}
}
if (otherPos != -1)
{
prev = (otherPos > 0) ? S.eventSet[otherPos - 1] : null;
next = (otherPos < S.eventSet.Count - 1) ? S.eventSet[otherPos + 1] : null;
}
switch (e.edgeType)
{
case EdgeType.NORMAL:
switch (operation)
{
case PolygonOp.INTERSECTION:
if (e.otherSE.inside)
{
connector.Add(e.segment);
}
break;
case PolygonOp.UNION:
if (!e.otherSE.inside)
{
connector.Add(e.segment);
}
break;
case PolygonOp.DIFFERENCE:
if ((e.polygonType == PolygonType.SUBJECT && !e.otherSE.inside) || (e.polygonType == PolygonType.CLIPPING && e.otherSE.inside))
{
connector.Add(e.segment);
}
break;
case PolygonOp.XOR:
connector.Add(e.segment);
break;
}
break;
case EdgeType.SAME_TRANSITION:
if (operation == PolygonOp.INTERSECTION || operation == PolygonOp.UNION)
{
connector.Add(e.segment);
}
break;
case EdgeType.DIFFERENT_TRANSITION:
if (operation == PolygonOp.DIFFERENCE)
{
connector.Add(e.segment);
}
break;
}
if (otherPos != -1)
{
S.Remove(S.eventSet[otherPos]);
}
if (next != null && prev != null)
{
PossibleIntersection(prev, next);
}
}
}
return(connector.ToPolygonFromLargestLineStrip());
}
void PossibleIntersection(SweepEvent e1, SweepEvent e2)
{
IntersectResult intData = FindIntersection(e1.segment, e2.segment);
int numIntersections = intData.max;
Point ip1 = intData.point1;
if (numIntersections == 0)
{
return;
}
if (numIntersections == 1 && (Point.EqualsBoth(e1.p, e2.p) || Point.EqualsBoth(e1.otherSE.p, e2.otherSE.p)))
{
return; // the line segments intersect at an endpoint of both line segments
}
if (numIntersections == 2 && e1.polygonType == e2.polygonType)
{
return; // the line segments overlap, but they belong to the same polygon
}
// The line segments associated to e1 and e2 intersect
if (numIntersections == 1)
{
if (!Point.EqualsBoth(e1.p, ip1) && !Point.EqualsBoth(e1.otherSE.p, ip1))
{
DivideSegment(e1, ip1); // if ip1 is not an endpoint of the line segment associated to e1 then divide "e1"
}
if (!Point.EqualsBoth(e2.p, ip1) && !Point.EqualsBoth(e2.otherSE.p, ip1))
{
DivideSegment(e2, ip1); // if ip1 is not an endpoint of the line segment associated to e2 then divide "e2"
}
return;
}
// The line segments overlap
sortedEvents.Clear();
if (Point.EqualsBoth(e1.p, e2.p))
{
sortedEvents.Add(null);
}
else if (Sec(e1, e2))
{
sortedEvents.Add(e2);
sortedEvents.Add(e1);
}
else
{
sortedEvents.Add(e1);
sortedEvents.Add(e2);
}
if (Point.EqualsBoth(e1.otherSE.p, e2.otherSE.p))
{
sortedEvents.Add(null);
}
else if (Sec(e1.otherSE, e2.otherSE))
{
sortedEvents.Add(e2.otherSE);
sortedEvents.Add(e1.otherSE);
}
else
{
sortedEvents.Add(e1.otherSE);
sortedEvents.Add(e2.otherSE);
}
if (sortedEvents.Count == 2) // are both line segments equal?
{
e1.edgeType = e1.otherSE.edgeType = EdgeType.NON_CONTRIBUTING;
e2.edgeType = e2.otherSE.edgeType = ((e1.inOut == e2.inOut) ? EdgeType.SAME_TRANSITION : EdgeType.DIFFERENT_TRANSITION);
return;
}
if (sortedEvents.Count == 3) // the line segments share an endpoint
{
sortedEvents[1].edgeType = sortedEvents[1].otherSE.edgeType = EdgeType.NON_CONTRIBUTING;
if (sortedEvents[0] != null) // is the right endpoint the shared point?
{
sortedEvents[0].otherSE.edgeType = (e1.inOut == e2.inOut) ? EdgeType.SAME_TRANSITION : EdgeType.DIFFERENT_TRANSITION;
}
else // the shared point is the left endpoint
{
sortedEvents[2].otherSE.edgeType = (e1.inOut == e2.inOut) ? EdgeType.SAME_TRANSITION : EdgeType.DIFFERENT_TRANSITION;
}
DivideSegment(sortedEvents[0] != null ? sortedEvents[0] : sortedEvents[2].otherSE, sortedEvents[1].p);
return;
}
if (!sortedEvents[0].Equals(sortedEvents[3].otherSE))
{ // no segment includes totally the otherSE one
sortedEvents[1].edgeType = EdgeType.NON_CONTRIBUTING;
sortedEvents[2].edgeType = (e1.inOut == e2.inOut) ? EdgeType.SAME_TRANSITION : EdgeType.DIFFERENT_TRANSITION;
DivideSegment(sortedEvents[0], sortedEvents[1].p);
DivideSegment(sortedEvents[1], sortedEvents[2].p);
return;
}
// one line segment includes the other one
sortedEvents[1].edgeType = sortedEvents[1].otherSE.edgeType = EdgeType.NON_CONTRIBUTING;
DivideSegment(sortedEvents[0], sortedEvents[1].p);
sortedEvents[3].otherSE.edgeType = (e1.inOut == e2.inOut) ? EdgeType.SAME_TRANSITION : EdgeType.DIFFERENT_TRANSITION;
DivideSegment(sortedEvents[3].otherSE, sortedEvents[2].p);
}
public SweepEvent(Point p, bool isLeft, PolygonType polygonType, SweepEvent otherSweepEvent) : this(p, isLeft, polygonType, otherSweepEvent, EdgeType.NORMAL)
{
}
