/// <summary>
/// For each edge in stack
/// (which must originate at a node)
/// extracts the line it initiates.
/// </summary>
private void BuildLines()
{
while (_nodeEdgeStack.Count > 0)
{
HalfEdge e = _nodeEdgeStack.Pop();
if (MarkHalfEdge.IsMarked(e))
{
continue;
}
BuildLine(e);
}
}
/// <summary>
/// Adds edges around this node to the stack.
/// </summary>
/// <param name="node"></param>
private void StackEdges(HalfEdge node)
{
HalfEdge e = node;
do
{
if (!MarkHalfEdge.IsMarked(e))
{
_nodeEdgeStack.Push(e);
}
e = e.ONext;
} while (e != node);
}
private void ComputeResult()
{
IEnumerable <HalfEdge> edges = _graph.GetVertexEdges();
foreach (HalfEdge e in edges)
{
if (MarkHalfEdge.IsMarked(e))
{
continue;
}
Process(e);
}
_result = _factory.BuildGeometry(_lines);
}
/// <summary>
/// Builds a line starting from the given edge.
/// The start edge origin is a node (valence = 1 or >= 3),
/// unless it is part of a pure ring.
/// </summary>
/// <remarks>
/// A pure ring has no other incident lines.
/// In this case the start edge may occur anywhere on the ring.
/// </remarks>
/// <remarks>
/// The line is built up to the next node encountered,
/// or until the start edge is re-encountered
/// (which happens if the edges form a ring).
/// </remarks>
/// <param name="eStart"></param>
private void BuildLine(HalfEdge eStart)
{
CoordinateList line = new CoordinateList();
DissolveHalfEdge e = (DissolveHalfEdge)eStart;
_ringStartEdge = null;
MarkHalfEdge.MarkBoth(e);
Coordinate orig = e.Orig;
line.Add(orig.Clone(), false);
// scan along the path until a node is found (if one exists)
while (e.Sym.Degree() == 2)
{
UpdateRingStartEdge(e);
DissolveHalfEdge eNext = (DissolveHalfEdge)e.Next;
// check if edges form a ring - if so, we're done
if (eNext == eStart)
{
BuildRing(_ringStartEdge);
return;
}
// add point to line, and move to next edge
orig = eNext.Orig;
line.Add(orig.Clone(), false);
e = eNext;
MarkHalfEdge.MarkBoth(e);
}
// add final node
Coordinate dest = e.Dest;
line.Add(dest.Clone(), false);
// queue up the final node edges
StackEdges(e.Sym);
// store the scanned line
AddLine(line);
}
