/// <summary>
/// Initializes a new instance of the <see cref="PresortedEventQueue" /> class.
/// </summary>
/// <param name="source">The source coordinates representing multiple line strings.</param>
/// <exception cref="System.ArgumentNullException">The source is null.</exception>
public PresortedEventQueue(IEnumerable <IList <Coordinate> > source)
{
// source: http://geomalgorithms.com/a09-_intersect-3.html
if (source == null)
{
throw new ArgumentNullException("source", "The source is null.");
}
_comparer = new CoordinateComparer();
_eventIndex = 0;
_eventList = new List <EndPointEvent>();
Int32 index = 0, compare;
foreach (IList <Coordinate> coordinateList in source)
{
if (coordinateList == null || coordinateList.Count < 2)
{
continue;
}
for (Int32 i = 0; i < coordinateList.Count - 1; i++)
{
var firstEvent = new EndPointEvent {
Edge = index, Vertex = coordinateList[i]
};
var secondEvent = new EndPointEvent {
Edge = index, Vertex = coordinateList[i + 1]
};
compare = _comparer.Compare(coordinateList[i], coordinateList[i + 1]);
if (compare == 0)
{
continue;
}
if (compare < 0)
{
firstEvent.Type = EventType.Left;
secondEvent.Type = EventType.Right;
}
else
{
firstEvent.Type = EventType.Right;
secondEvent.Type = EventType.Left;
}
_eventList.Add(firstEvent);
_eventList.Add(secondEvent);
index++;
}
index++;
}
_eventList.Sort(new EventComparer());
}
/// <summary>
/// Adds a new endpoint event to the sweep line.
/// </summary>
/// <param name="e">The event.</param>
/// <returns>The sweep line segment created by addition of <paramref name="e" />.</returns>
/// <exception cref="System.ArgumentNullException">e;The event is null.</exception>
/// <exception cref="System.ArgumentException">
/// The edge of the event is less than 0.;e
/// or
/// The edge of the event is greater than the number of edges in the source.;e
/// </exception>
public SweepLineSegment Add(EndPointEvent e)
{
// source: http://geomalgorithms.com/a09-_intersect-3.html
if (e == null)
{
throw new ArgumentNullException("e", "The event is null.");
}
if (e.Edge < 0)
{
throw new ArgumentException("The edge of the event is less than 0.", "e");
}
if (e.Edge >= _source.Count - 1)
{
throw new ArgumentException("The edge of the event is greater than the number of edges in the source.", "e");
}
SweepLineSegment segment = new SweepLineSegment {
Edge = e.Edge
};
Coordinate c1 = _source[e.Edge];
Coordinate c2 = _source[e.Edge + 1];
if (_coordinateComparer.Compare(c1, c2) <= 0)
{
segment.LeftCoordinate = c1;
segment.RightCoordinate = c2;
}
else
{
segment.LeftCoordinate = c2;
segment.RightCoordinate = c1;
}
_tree.Insert(segment);
SweepLineSegment segmentAbove = _tree.GetNext();
SweepLineSegment segmentBelow = _tree.GetPrev();
if (segmentAbove != null)
{
segment.Above = segmentAbove;
segment.Above.Below = segment;
}
if (segmentBelow != null)
{
segment.Below = segmentBelow;
segment.Below.Above = segment;
}
return(segment);
}
/// <summary>
/// Searches the sweep line for an endpoint event.
/// </summary>
/// <param name="e">The event.</param>
/// <returns>The segment associated with the event.</returns>
/// <exception cref="System.ArgumentNullException">e;The event is null.</exception>
/// <exception cref="System.ArgumentException">
/// The edge of the event is less than 0.
/// or
/// The edge of the event is greater than the number of edges in the source.
/// </exception>
public SweepLineSegment Search(EndPointEvent e)
{
if (e == null)
{
throw new ArgumentNullException("e", "The event is null.");
}
if (e.Edge < 0)
{
throw new ArgumentException("The edge of the event is less than 0.", "e");
}
if (e.Edge >= _source.Count - 1)
{
throw new ArgumentException("The edge of the event is greater than the number of edges in the source.", "e");
}
SweepLineSegment segment = new SweepLineSegment()
{
Edge = e.Edge
};
Coordinate c1 = _source[e.Edge];
Coordinate c2 = _source[e.Edge + 1];
if (_coordinateComparer.Compare(c1, c2) < 0)
{
segment.LeftCoordinate = c1;
segment.RightCoordinate = c2;
}
else
{
segment.LeftCoordinate = c2;
segment.RightCoordinate = c1;
}
SweepLineSegment segmentResult;
if (_tree.TrySearch(segment, out segmentResult))
{
return(segmentResult);
}
else
{
return(null);
}
}
/// <summary>
/// Initializes a new instance of the <see cref="EventQueue" /> class.
/// </summary>
/// <param name="source">The source coordinates representing a single line string.</param>
/// <exception cref="System.ArgumentNullException">The source is null.</exception>
public EventQueue(IList <Coordinate> source)
{
// source: http://geomalgorithms.com/a09-_intersect-3.html
if (source == null)
{
throw new ArgumentNullException("source", "The source is null.");
}
_comparer = new CoordinateComparer();
_eventHeap = new EventHeap();
Int32 compare;
for (Int32 i = 0; i < source.Count - 1; i++)
{
EndPointEvent firstEvent = new EndPointEvent {
Edge = i, Vertex = source[i]
};
EndPointEvent secondEvent = new EndPointEvent {
Edge = i, Vertex = source[i + 1]
};
compare = _comparer.Compare(source[i], source[i + 1]);
if (compare == 0)
{
continue;
}
if (compare < 0)
{
firstEvent.Type = EventType.Left;
secondEvent.Type = EventType.Right;
}
else
{
firstEvent.Type = EventType.Right;
secondEvent.Type = EventType.Left;
}
_eventHeap.Insert(firstEvent);
_eventHeap.Insert(secondEvent);
}
}
/// <summary>
/// Compares two <see cref="Event"/> instances and returns a value indicating whether one is less than, equal to, or greater than the other.
/// </summary>
/// <remarks>
/// Events primarily compared by their vertex coordinate, secondarily by their type.
/// </remarks>
/// <param name="x">The first <see cref="Event"/> to compare.</param>
/// <param name="y">The second <see cref="Event"/> to compare.</param>
/// <returns>A signed integer that indicates the relative values of <paramref name="x"/> and <paramref name="y"/>.</returns>
public Int32 Compare(Event x, Event y)
{
Int32 result = _coordinateComparer.Compare(x.Vertex, y.Vertex);
if (result != 0)
{
return(result);
}
if (x is EndPointEvent && y is EndPointEvent)
{
EndPointEvent ex = (EndPointEvent)x;
EndPointEvent ey = (EndPointEvent)y;
result = ex.Type.CompareTo(ey.Type);
if (result == 0)
{
result = ex.Edge.CompareTo(ey.Edge);
}
}
else if (x is IntersectionEvent && y is IntersectionEvent)
{
IntersectionEvent ix = (IntersectionEvent)x;
IntersectionEvent iy = (IntersectionEvent)y;
if (result == 0)
{
result = _coordinateComparer.Compare(ix.Below.LeftCoordinate, iy.Below.LeftCoordinate);
}
if (result == 0)
{
result = _coordinateComparer.Compare(ix.Above.LeftCoordinate, iy.Above.LeftCoordinate);
}
if (result == 0)
{
result = _coordinateComparer.Compare(ix.Below.RightCoordinate, iy.Below.RightCoordinate);
}
if (result == 0)
{
result = _coordinateComparer.Compare(ix.Above.RightCoordinate, iy.Above.RightCoordinate);
}
if (result == 0)
{
result = ix.Below.Edge.CompareTo(iy.Below.Edge);
}
if (result == 0)
{
result = ix.Above.Edge.CompareTo(iy.Above.Edge);
}
if (result == 0)
{
result = ix.IsClose.CompareTo(iy.IsClose);
}
}
else if (x is EndPointEvent && y is IntersectionEvent)
{
result = ((EndPointEvent)x).Type == EventType.Left ? -1 : 1;
}
else if (y is EndPointEvent && x is IntersectionEvent)
{
result = ((EndPointEvent)y).Type == EventType.Left ? 1 : -1;
}
return(result);
}
