/// <summary>
/// Gets the segment at the vertices provided if it exists, or creates
/// it if not.
/// </summary>
/// <param name="start">The start vertex.</param>
/// <param name="end">The end vertex.</param>
/// <param name="line">The line (optional).</param>
/// <returns>Either a newly allocated BSP segment, or the one that
/// already exists with the information provided.</returns>
public BspSegment GetOrCreate(BspVertex start, BspVertex end, IBspUsableLine line = null)
{
Debug.Assert(start != end, "Cannot create a segment that is a point");
(int smallerIndex, int largerIndex) = start.Index.MinMax(end.Index);
if (segmentTable.TryGetValue(smallerIndex, out var largerValues))
{
if (largerValues.TryGetValue(largerIndex, out int segIndex))
{
return(segments[segIndex]);
}
largerValues[largerIndex] = segments.Count;
int newCollinearIndex = GetCollinearIndex(start, end);
return(CreateNewSegment(start, end, newCollinearIndex, line));
}
var largerIndexDict = new Dictionary <int, int> {
[largerIndex] = segments.Count
};
int collinearIndex = GetCollinearIndex(start, end);
segmentTable[smallerIndex] = largerIndexDict;
return(CreateNewSegment(start, end, collinearIndex, line));
}
private BspSegment CreateNewSegment(BspVertex start, BspVertex end, int collinearIndex,
IBspUsableLine line = null)
{
BspSegment seg = new BspSegment(start, end, collinearIndex, line);
segments.Add(seg);
return(seg);
}
/// <summary>
/// Checks if a segment exists with the start/end index combination.
/// The order of the indices does not matter.
/// </summary>
/// <param name="start">The start index.</param>
/// <param name="end">The end index.</param>
/// <returns>True if a segment (start, end) or (end, start) exists in
/// this allocator, false otherwise.</returns>
public bool ContainsSegment(BspVertex start, BspVertex end)
{
(int smallerIndex, int largerIndex) = start.Index.MinMax(end.Index);
if (segmentTable.TryGetValue(smallerIndex, out var largerValues))
{
return(largerValues.ContainsKey(largerIndex));
}
return(false);
}
/// <summary>
/// Performs a split on the segment at some time t (which should be in
/// the normal range).
/// </summary>
/// <param name="seg">The segment to split.</param>
/// <param name="t">The time to split at, which should be in (0, 1). It
/// is an error for it to be equal to 0.0 or 1.0 as that would create
/// a point for a segment (which is no longer a segment).</param>
/// <returns>The two segments, where the first element is the segment
/// from [start, middle], and the second segment element is from the
/// [middle, end].</returns>
public (BspSegment first, BspSegment second) Split(BspSegment seg, double t)
{
Debug.Assert(t > 0.0 && t < 1.0, "Trying to split BSP out of the (0.0, 1.0) range");
Vec2D middle = seg.FromTime(t);
BspVertex middleVertex = vertexAllocator[middle];
BspSegment firstSeg = GetOrCreate(seg.StartVertex, middleVertex, seg.Line.Value);
BspSegment secondSeg = GetOrCreate(middleVertex, seg.EndVertex, seg.Line.Value);
return(firstSeg, secondSeg);
}
private int GetCollinearIndex(BspVertex start, BspVertex end)
{
return(collinearTracker.GetOrCreateIndex(start, end));
}