void ComputeVisiblePartOfTheHole(Polyline hole)
{
//find a separating edge
PolylinePoint a;
var needToGoCounterclockWise = true;
for (a = hole.StartPoint; !HoleSideIsVisibleFromQ(hole, a); a = hole.Next(a))
{
Debug.Assert(needToGoCounterclockWise || a != hole.StartPoint);
//check that we have not done the full circle
needToGoCounterclockWise = false;
}
PolylinePoint b = hole.Next(a);
//now the side a, a.Next - is separating
if (needToGoCounterclockWise)
{
while (HoleSideIsVisibleFromQ(hole, hole.Prev(a)))
{
a = hole.Prev(a);
}
}
//go clockwise starting from b
for (; HoleSideIsVisibleFromQ(hole, b); b = hole.Next(b))
{
}
visibleBoundaries[hole] = new Stem(a, b);
}
IEnumerable <Stem> GetInitialVisibleBoundaryStemsAndInsertActiveSides()
{
foreach (var keyValuePair in visibleBoundaries)
{
Polyline hole = keyValuePair.Key;
Stem stem = keyValuePair.Value;
bool crosses = false;
foreach (PolylinePoint side in stem.Sides)
{
PolylinePoint source = side;
if (source.Point.Y < q.Y)
{
if (side.NextOnPolyline.Point.Y >= q.Y)
{
TriangleOrientation orientation = Point.GetTriangleOrientation(q, source.Point,
side.NextOnPolyline.Point);
if (orientation == TriangleOrientation.Counterclockwise ||
orientation == TriangleOrientation.Collinear)
{
crosses = true;
//we have two stems here
yield return(new Stem(stem.Start, side));
yield return(new Stem(side.NextOnPolyline, stem.End));
RegisterActiveSide(side);
break;
}
}
}
else if (source.Point.Y > q.Y)
{
break;
}
else if (side.Point.X >= q.X)
{
//we have pp.Y==q.Y
crosses = true;
//we need to add one or two stems here
yield return(new Stem(side, stem.End));
if (side != stem.Start)
{
yield return(new Stem(stem.Start, hole.Prev(source)));
}
RegisterActiveSide(side);
break;
}
}
//there is no intersection with the ray
if (!crosses)
{
yield return(stem);
}
}
}
PolylinePoint GetOutgoingSide(PolylinePoint v)
{
Stem visibleStem = visibleBoundaries[v.Polyline];
if (v == visibleStem.End)
{
return(null);
}
return(v);
}
void SortSAndInitActiveSides()
{
InitHeapAndInsertActiveSides();
for (Stem stem = heapForSorting.GetMinimum();; stem = heapForSorting.GetMinimum())
{
sortedListOfPolypoints.Add(stem.Start);
if (stem.MoveStartClockwise())
{
heapForSorting.ChangeMinimum(stem);
}
else
{
heapForSorting.Dequeue();
}
if (heapForSorting.Count == 0)
{
break;
}
}
}
void ComputeVisiblePartOfTheHole(Polyline hole) {
//find a separating edge
PolylinePoint a;
var needToGoCounterclockWise = true;
for (a = hole.StartPoint; !HoleSideIsVisibleFromQ(hole, a); a = hole.Next(a)) {
Debug.Assert(needToGoCounterclockWise || a != hole.StartPoint);
//check that we have not done the full circle
needToGoCounterclockWise = false;
}
PolylinePoint b = hole.Next(a);
//now the side a, a.Next - is separating
if (needToGoCounterclockWise)
while (HoleSideIsVisibleFromQ(hole, hole.Prev(a)))
a = hole.Prev(a);
//go clockwise starting from b
for (; HoleSideIsVisibleFromQ(hole, b); b = hole.Next(b)) {}
visibleBoundaries[hole] = new Stem(a, b);
}