private static PolygonCrossing FindPreviousCrossingNotEqual(
PolygonCrossing currentCrossing,
PolygonCrossing[] crossingsOnRing,
IComparer <PolygonCrossing> crossingComparer
)
{
Contract.Requires(currentCrossing != null);
Contract.Requires(crossingsOnRing != null);
Contract.Requires(Contract.ForAll(crossingsOnRing, x => x != null));
Contract.Requires(crossingComparer != null);
var currentPoint = currentCrossing.Point;
int currentCrossingIndex = Array.BinarySearch(crossingsOnRing, currentCrossing, crossingComparer);
if (currentCrossingIndex < 0)
{
return(null);
}
int crossingsCount = crossingsOnRing.Length;
// find the first crossing before this one that has a different point location
for (
int i = IterationUtils.RetreatLoopingIndex(currentCrossingIndex, crossingsCount);
i != currentCrossingIndex;
i = IterationUtils.RetreatLoopingIndex(i, crossingsCount)
)
{
var crossing = crossingsOnRing[i];
if (crossing.Point != currentPoint)
{
return(crossing);
}
}
return(null);
}
private PolygonCrossing TraverseBSideHops(PolygonCrossing start)
{
Contract.Requires(start != null);
PolygonCrossing current = start;
PolygonCrossing result = null;
PolygonCrossing next;
while (
Exits.Contains(current) &&
ExitHops.TryGetValue(current, out next) &&
Entrances.Contains(next) &&
next.LocationB != start.LocationB
)
{
result = next;
VisitEntrance(next);
Contract.Assume(current != null);
VisitExit(current);
if (!EntranceHops.TryGetValue(next, out current))
{
break;
}
}
return(result);
}
private static Point2 FindNextRingPoint(
PolygonCrossing currentCrossing,
PolygonCrossing[] crossingsOnRing,
Ring2 ring,
Func <PolygonCrossing, PolygonBoundaryLocation> getLocation,
IComparer <PolygonCrossing> crossingComparer
)
{
Contract.Requires(currentCrossing != null);
Contract.Requires(crossingsOnRing != null);
Contract.Requires(Contract.ForAll(crossingsOnRing, x => x != null));
Contract.Requires(ring != null);
Contract.Requires(getLocation != null);
Contract.Requires(crossingComparer != null);
var currentLocation = getLocation(currentCrossing);
var segmentCount = ring.SegmentCount;
int nextSegmentIndex = IterationUtils.AdvanceLoopingIndex(currentLocation.SegmentIndex, segmentCount);
var nextCrossing = FindNextCrossingNotEqual(currentCrossing, crossingsOnRing, crossingComparer);
// NOTE: this method assumes a segment ratio less than 1, verify we can trust this
if (null == nextCrossing)
{
return(ring[nextSegmentIndex]);
}
var nextCrossingLocation = getLocation(nextCrossing);
Contract.Assume(nextCrossingLocation != null);
return(currentLocation.SegmentIndex == nextCrossingLocation.SegmentIndex &&
currentLocation.SegmentRatio < nextCrossingLocation.SegmentRatio
? nextCrossing.Point
: ring[nextSegmentIndex]);
}
private void ApplyCrossingVisit(PolygonCrossing crossing)
{
Contract.Requires(crossing != null);
VisitedCrossings.Add(crossing);
VisitedCrossingsRingIndicesA.Add(crossing.LocationA.RingIndex);
VisitedCrossingsRingIndicesB.Add(crossing.LocationB.RingIndex);
}
private void VisitExit(PolygonCrossing exit)
{
Contract.Requires(exit != null);
if (Exits.Remove(exit))
{
ApplyCrossingVisit(exit);
}
}
private void VisitEntrance(PolygonCrossing entrance)
{
Contract.Requires(entrance != null);
if (Entrances.Remove(entrance))
{
ApplyCrossingVisit(entrance);
}
}
private static IEnumerable <PolygonCrossing> TraverseCrossings(
PolygonCrossing fromCrossing,
PolygonCrossing[] ringCrossings,
int fromCrossingIndex
)
{
Contract.Requires(fromCrossing != null);
Contract.Requires(ringCrossings != null);
//Contract.Requires(crossingComparer != null);
Contract.Requires(fromCrossingIndex >= 0);
Contract.Ensures(Contract.Result <IEnumerable <PolygonCrossing> >() != null);
//var fromCrossingIndex = ringCrossings.BinarySearch(fromCrossing, crossingComparer);
var ringCrossingsCount = ringCrossings.Length;
Stack <PolygonCrossing> priorResults = null;
var backTrackIndex = fromCrossingIndex;
do
{
var priorIndex = IterationUtils.RetreatLoopingIndex(backTrackIndex, ringCrossingsCount);
var priorCrossing = ringCrossings[priorIndex];
if (priorCrossing.Point != fromCrossing.Point)
{
break;
}
backTrackIndex = priorIndex;
(priorResults ?? (priorResults = new Stack <PolygonCrossing>()))
.Push(priorCrossing);
} while (backTrackIndex != fromCrossingIndex);
if (null != priorResults)
{
while (priorResults.Count > 0)
{
yield return(priorResults.Pop());
}
}
for (
int i = IterationUtils.AdvanceLoopingIndex(fromCrossingIndex, ringCrossingsCount);
i != fromCrossingIndex;
i = IterationUtils.AdvanceLoopingIndex(i, ringCrossingsCount)
)
{
yield return(ringCrossings[i]);
}
}
private PolygonCrossing TraverseBSideRing(
List <Point2> buildingRing,
PolygonCrossing fromCrossing,
PolygonCrossing[] ringCrossings
)
{
Contract.Requires(buildingRing != null);
Contract.Requires(fromCrossing != null);
Contract.Requires(ringCrossings != null);
Contract.Requires(Contract.ForAll(ringCrossings, x => x != null));
Contract.Ensures(buildingRing.Count >= Contract.OldValue(buildingRing).Count);
var fromSegmentLocationB = fromCrossing.LocationB;
if (0 == buildingRing.Count || buildingRing[buildingRing.Count - 1] != fromCrossing.Point)
{
buildingRing.Add(fromCrossing.Point);
}
var fromCrossingIndex = Array.BinarySearch(ringCrossings, fromCrossing, PolygonCrossing.LocationBComparer.Default);
Contract.Assume(fromCrossingIndex >= 0);
foreach (var crossing in TraverseCrossings(fromCrossing, ringCrossings, fromCrossingIndex))
{
// hops should have already been taken care of
if (crossing.Point == fromCrossing.Point && ExitHops.ContainsKey(crossing))
{
continue; // no, lets go somewhere useful with this
}
var locationB = crossing.LocationB;
Contract.Assume(locationB.RingIndex < B.Count);
Contract.Assume(B[locationB.RingIndex] != null);
AddPointsBetweenForward(buildingRing, B[locationB.RingIndex], fromSegmentLocationB, locationB);
fromSegmentLocationB = locationB; // for later...
if (Exits.Contains(crossing))
{
return(crossing); // if we found it, stop
}
if (buildingRing.Count == 0 || buildingRing[buildingRing.Count - 1] != crossing.Point)
{
buildingRing.Add(crossing.Point); // if it is something else, lets add it
}
}
return(null);
}
private static Point2 FindPreviousRingPoint(
PolygonCrossing currentCrossing,
PolygonCrossing[] crossingsOnRing,
Ring2 ring,
Func <PolygonCrossing, PolygonBoundaryLocation> getLocation,
IComparer <PolygonCrossing> crossingComparer
)
{
Contract.Requires(currentCrossing != null);
Contract.Requires(crossingsOnRing != null);
Contract.Requires(Contract.ForAll(crossingsOnRing, x => x != null));
Contract.Requires(ring != null);
Contract.Requires(getLocation != null);
Contract.Requires(crossingComparer != null);
var currentLocation = getLocation(currentCrossing);
var segmentCount = ring.SegmentCount;
Contract.Assume(currentLocation.SegmentIndex < segmentCount);
var previousSegmentIndex = IterationUtils.RetreatLoopingIndex(currentLocation.SegmentIndex, segmentCount);
var previousCrossing = FindPreviousCrossingNotEqual(currentCrossing, crossingsOnRing, crossingComparer);
if (null == previousCrossing)
{
return(ring[
currentLocation.SegmentRatio == 0
? previousSegmentIndex
: currentLocation.SegmentIndex
]);
}
var previousCrossingLocation = getLocation(previousCrossing);
Contract.Assume(previousCrossingLocation != null);
if (currentLocation.SegmentRatio == 0)
{
return(previousSegmentIndex == previousCrossingLocation.SegmentIndex
? previousCrossing.Point
: ring[previousSegmentIndex]);
}
return(currentLocation.SegmentIndex == previousCrossingLocation.SegmentIndex &&
currentLocation.SegmentRatio > previousCrossingLocation.SegmentRatio
? previousCrossing.Point
: ring[currentLocation.SegmentIndex]);
}
public PolygonCrossing[] Get(int ringIndex)
{
Contract.Requires(ringIndex >= 0);
Contract.Ensures(Contract.Result <PolygonCrossing[]>() != null);
Contract.Ensures(Contract.ForAll(Contract.Result <PolygonCrossing[]>(), x => x != null));
if (_cache.Key == ringIndex)
{
return(_cache.Value);
}
PolygonCrossing[] crossings;
if (!RingCrossings.TryGetValue(ringIndex, out crossings))
{
crossings = new PolygonCrossing[0];
}
_cache = new KeyValuePair <int, PolygonCrossing[]>(ringIndex, crossings);
Contract.Assume(crossings != null);
return(crossings);
}
private PolygonCrossing TraverseBSide(
PolygonCrossing entrance,
List <Point2> buildingRing
)
{
Contract.Requires(entrance != null);
Contract.Requires(buildingRing != null);
Contract.Ensures(buildingRing.Count >= Contract.OldValue(buildingRing).Count);
PolygonCrossing exit;
do
{
exit = TraverseBSideRing(buildingRing, entrance, RingCrossingsB.Get(entrance.LocationB.RingIndex));
if (exit == null)
{
return(null);
}
} while ((entrance = TraverseBSideHops(exit)) != null);
return(exit);
}
/// <summary>
/// Builds required crossing data.
/// </summary>
/// <param name="crossings">The crossings to calculate. (Note: collection is modified)</param>
/// <param name="a">The left hand polygon.</param>
/// <param name="b">The right hand polygon.</param>
private PolygonCrossingsAlgorithmKernel CreateIntersectionKernelFromCrossings(List <PolygonCrossing> crossings, Polygon2 a, Polygon2 b)
{
Contract.Requires(crossings != null);
Contract.Requires(a != null);
Contract.Requires(b != null);
Contract.Ensures(Contract.Result <PolygonCrossingsAlgorithmKernel>() != null);
var kernel = new PolygonCrossingsAlgorithmKernel(a, b, crossings);
if (crossings.Count == 0)
{
return(kernel);
}
foreach (var currentCrossing in crossings)
{
var ringIndexA = currentCrossing.LocationA.RingIndex;
Contract.Assume(ringIndexA < a.Count);
var ringA = a[ringIndexA];
Contract.Assume(ringA != null);
var crossingsOnRingA = kernel.RingCrossingsA.Get(ringIndexA);
var priorPointA = FindPreviousRingPoint(currentCrossing, crossingsOnRingA, ringA, GetLocationA, PolygonCrossing.LocationAComparer.Default);
var nextPointA = FindNextRingPoint(currentCrossing, crossingsOnRingA, ringA, GetLocationA, PolygonCrossing.LocationAComparer.Default);
var ringIndexB = currentCrossing.LocationB.RingIndex;
Contract.Assume(ringIndexB < b.Count);
var ringB = b[ringIndexB];
Contract.Assume(ringB != null);
var crossingsOnRingB = kernel.RingCrossingsB.Get(ringIndexB);
var priorPointB = FindPreviousRingPoint(currentCrossing, crossingsOnRingB, ringB, GetLocationB, PolygonCrossing.LocationBComparer.Default);
var nextPointB = FindNextRingPoint(currentCrossing, crossingsOnRingB, ringB, GetLocationB, PolygonCrossing.LocationBComparer.Default);
// based on the vectors, need to classify the crossing type
currentCrossing.CrossType = PolygonCrossing.DetermineCrossingType(
(nextPointA - currentCrossing.Point).GetNormalized(),
(priorPointA - currentCrossing.Point).GetNormalized(),
(nextPointB - currentCrossing.Point).GetNormalized(),
(priorPointB - currentCrossing.Point).GetNormalized()
);
}
foreach (var ringCrossings in kernel.RingCrossingsA.RingCrossings)
{
Contract.Assume(ringCrossings.Key >= 0 && ringCrossings.Key < a.Count);
if (a[ringCrossings.Key].FillSide == RelativeDirectionType.Right)
{
foreach (var crossing in ringCrossings.Value)
{
Contract.Assume(crossing != null);
var crossLegType = crossing.CrossType & CrossingType.Parallel;
if (crossLegType == CrossingType.CrossToRight || crossLegType == CrossingType.DivergeRight)
{
kernel.Entrances.Add(crossing);
}
else if (crossLegType == CrossingType.CrossToLeft || crossLegType == CrossingType.ConvergeRight)
{
kernel.Exits.Add(crossing);
}
}
}
else
{
foreach (var crossing in ringCrossings.Value)
{
Contract.Assume(crossing != null);
var crossLegType = crossing.CrossType & CrossingType.Parallel;
if (crossLegType == CrossingType.CrossToLeft || crossLegType == CrossingType.DivergeLeft)
{
kernel.Entrances.Add(crossing);
}
else if (crossLegType == CrossingType.CrossToRight || crossLegType == CrossingType.ConvergeLeft)
{
kernel.Exits.Add(crossing);
}
}
}
}
var sortedEntrances = kernel.Entrances.ToArray();
Array.Sort(sortedEntrances, PolygonCrossing.LocationAComparer.CompareNonNull);
Contract.Assume(kernel.Exits != null);
var sortedExits = kernel.Exits.ToArray();
Array.Sort(sortedExits, PolygonCrossing.LocationBComparer.CompareNonNull);
for (int i = 0; i < sortedExits.Length; i++)
{
var exit = sortedExits[i];
var locationIndex = Array.BinarySearch(sortedEntrances, exit, PolygonCrossing.LocationAComparer.Default);
if (locationIndex >= 0)
{
kernel.ExitHops.Add(exit, sortedEntrances[locationIndex]);
}
}
for (int i = 0; i < sortedEntrances.Length; i++)
{
var entrance = sortedEntrances[i];
var locationIndex = Array.BinarySearch(sortedExits, entrance, PolygonCrossing.LocationBComparer.Default);
if (locationIndex >= 0)
{
kernel.EntranceHops.Add(entrance, sortedExits[locationIndex]);
}
}
return(kernel);
}
[Pure] private static int GetRingIndexB(PolygonCrossing crossing)
{
Contract.Requires(crossing != null);
Contract.Ensures(Contract.Result <int>() >= 0);
return(crossing.LocationB.RingIndex);
}
[Pure] private static PolygonBoundaryLocation GetLocationB(PolygonCrossing crossing)
{
Contract.Requires(crossing != null);
Contract.Ensures(Contract.Result <PolygonBoundaryLocation>() != null);
return(crossing.LocationB);
}