IEnumerable <Point> Calculate()
{
if (pivot.Y == Double.MaxValue)
{
return(new Point[0]);
}
if (hullPoints.Length == 0)
{
return new[] { pivot }
}
;
SortAllPointsWithoutPivot();
Scan();
return(EnumerateStack());
}
IEnumerable <Point> EnumerateStack()
{
HullStack stackCell = stack;
while (stackCell != null)
{
yield return(stackCell.Point);
stackCell = stackCell.Next;
}
}
void Scan()
{
int i = 0;
while (hullPoints[i].Deleted)
{
i++;
}
stack = new HullStack(pivot);
Push(i++);
if (i < hullPoints.Length)
{
if (!hullPoints[i].Deleted)
{
Push(i++);
}
else
{
i++;
}
}
while (i < hullPoints.Length)
{
if (!hullPoints[i].Deleted)
{
if (LeftTurn(i))
{
Push(i++);
}
else
{
Pop();
}
}
else
{
i++;
}
}
//cleanup the end
while (StackHasMoreThanTwoPoints() && !LeftTurnToPivot())
{
Pop();
}
}
bool LeftTurnToPivot()
{
return(Point.GetTriangleOrientation(StackSecondPoint, StackTopPoint, pivot) ==
TriangleOrientation.Counterclockwise);
}
bool StackHasMoreThanTwoPoints()
{
return(stack.Next != null && stack.Next.Next != null);
}
void Pop()
{
stack = stack.Next;
}
bool LeftTurn(int i)
{
if (stack.Next == null)
{
return(true); //there is only one point in the stack
}
var orientation = Point.GetTriangleOrientationWithIntersectionEpsilon(StackSecondPoint, StackTopPoint, hullPoints[i].Point);
if (orientation == TriangleOrientation.Counterclockwise)
{
return(true);
}
if (orientation == TriangleOrientation.Clockwise)
{
return(false);
}
return(BackSwitchOverPivot(hullPoints[i].Point));
}
bool BackSwitchOverPivot(Point point)
{
//we know here that there at least two points in the stack but it has to be exaclty two
if (stack.Next.Next != null)
{
return(false);
}
Debug.Assert(StackSecondPoint == pivot);
return(StackTopPoint.X > pivot.X + ApproximateComparer.DistanceEpsilon &&
point.X < pivot.X - ApproximateComparer.DistanceEpsilon);
}
void Push(int p)
{
var t = new HullStack(hullPoints[p].Point)
{
Next = stack
};
stack = t;
}
void SortAllPointsWithoutPivot()
{
comparer = new HullPointComparer(pivot);
Array.Sort(hullPoints, comparer);
// if (true) {
// var list = new List<DebugCurve>();
// var d = 3.0;
// list.Add(new DebugCurve(100, 0.001, "magenta", El(ref d, pivot)));
// foreach (var hullPoint in hullPoints) {
// list.Add(new DebugCurve(100,0.001, hullPoint.Deleted ? "blue" : "green", El(ref d, hullPoint.Point)));
// }
// LayoutAlgorithmSettings.ShowDebugCurvesEnumeration(list);
// }
}
void Push(int p) {
var t = new HullStack(hullPoints[p].Point) {Next = stack};
stack = t;
}
void Scan() {
int i = 0;
while (hullPoints[i].Deleted)
i++;
stack = new HullStack(pivot);
Push(i++);
if (i < hullPoints.Length) {
if (!hullPoints[i].Deleted)
Push(i++);
else
i++;
}
while (i < hullPoints.Length) {
if (!hullPoints[i].Deleted) {
if (LeftTurn(i))
Push(i++);
else
Pop();
}
else
i++;
}
//cleanup the end
while (StackHasMoreThanTwoPoints() && !LeftTurnToPivot())
Pop();
}
void Pop() {
stack = stack.Next;
}