/// <summary>
/// Decompose graph into simple polylines and polygons.
/// </summary>
public static CurveCollection ExtractCurves(DGraph2 graph)
{
CurveCollection c = new CurveCollection();
HashSet <int> used = new HashSet <int>();
// find boundary and junction vertices
HashSet <int> boundaries = new HashSet <int>();
HashSet <int> junctions = new HashSet <int>();
foreach (int vid in graph.VertexIndices())
{
if (graph.IsBoundaryVertex(vid))
{
boundaries.Add(vid);
}
if (graph.IsJunctionVertex(vid))
{
junctions.Add(vid);
}
}
// walk paths from boundary vertices
foreach (int start_vid in boundaries)
{
int vid = start_vid;
int eid = graph.GetVtxEdges(vid)[0];
if (used.Contains(eid))
{
continue;
}
PolyLine2d path = new PolyLine2d();
path.AppendVertex(graph.GetVertex(vid));
while (true)
{
used.Add(eid);
Index2i next = NextEdgeAndVtx(eid, vid, graph);
eid = next.a;
vid = next.b;
path.AppendVertex(graph.GetVertex(vid));
if (boundaries.Contains(vid) || junctions.Contains(vid))
{
break; // done!
}
}
c.Paths.Add(path);
}
// ok we should be done w/ boundary verts now...
boundaries.Clear();
foreach (int start_vid in junctions)
{
foreach (int outgoing_eid in graph.VtxEdgesItr(start_vid))
{
if (used.Contains(outgoing_eid))
{
continue;
}
int vid = start_vid;
int eid = outgoing_eid;
PolyLine2d path = new PolyLine2d();
path.AppendVertex(graph.GetVertex(vid));
bool is_loop = false;
while (true)
{
used.Add(eid);
Index2i next = NextEdgeAndVtx(eid, vid, graph);
eid = next.a;
vid = next.b;
if (vid == start_vid)
{
is_loop = true;
break;
}
path.AppendVertex(graph.GetVertex(vid));
if (eid == int.MaxValue || junctions.Contains(vid))
{
break;
}
}
if (is_loop)
{
c.Loops.Add(new Polygon2d(path.Vertices));
}
else
{
c.Paths.Add(path);
}
}
}
// all that should be left are continuous loops...
foreach (int start_eid in graph.EdgeIndices())
{
if (used.Contains(start_eid))
{
continue;
}
int eid = start_eid;
Index2i ev = graph.GetEdgeV(eid);
int vid = ev.a;
Polygon2d poly = new Polygon2d();
poly.AppendVertex(graph.GetVertex(vid));
while (true)
{
used.Add(eid);
Index2i next = NextEdgeAndVtx(eid, vid, graph);
eid = next.a;
vid = next.b;
poly.AppendVertex(graph.GetVertex(vid));
if (eid == int.MaxValue || junctions.Contains(vid))
{
throw new Exception("how did this happen??");
}
if (used.Contains(eid))
{
break;
}
}
poly.RemoveVertex(poly.VertexCount - 1);
c.Loops.Add(poly);
}
return(c);
}
public void Add(CurveCollection other)
{
Loops.AddRange(other.Loops);
Paths.AddRange(other.Paths);
}
public static void ChainOpenPaths(CurveCollection c, double epsilon = MathUtil.Epsilon)
{
List <PolyLine2d> to_process = new List <PolyLine2d>(c.Paths);
c.Paths.Clear();
// first we separate out 'dangling' curves that have no match on at least one side
List <PolyLine2d> dangling = new List <PolyLine2d>();
List <PolyLine2d> remaining = new List <PolyLine2d>();
bool bContinue = true;
while (bContinue && to_process.Count > 0)
{
bContinue = false;
foreach (PolyLine2d p in to_process)
{
var matches_start = find_connected_start(p, to_process, epsilon);
var matches_end = find_connected_end(p, to_process, epsilon);
if (matches_start.Count == 0 || matches_end.Count == 0)
{
dangling.Add(p);
bContinue = true;
}
else
{
remaining.Add(p);
}
}
to_process.Clear(); to_process.AddRange(remaining); remaining.Clear();
}
//to_process.Clear(); to_process.AddRange(remaining); remaining.Clear();
// now incrementally merge together unique matches
// [TODO] this will not match across junctions!
bContinue = true;
while (bContinue && to_process.Count > 0)
{
bContinue = false;
restart_itr:
foreach (PolyLine2d p in to_process)
{
var matches_start = find_connected_start(p, to_process, epsilon);
var matches_end = find_connected_end(p, to_process, 2 * epsilon);
if (matches_start.Count == 1 && matches_end.Count == 1 &&
matches_start[0] == matches_end[0])
{
c.Loops.Add(to_loop(p, matches_start[0], epsilon));
to_process.Remove(p);
to_process.Remove(matches_start[0]);
remaining.Remove(matches_start[0]);
bContinue = true;
goto restart_itr;
}
else if (matches_start.Count == 1 && matches_end.Count < 2)
{
remaining.Add(merge_paths(matches_start[0], p, 2 * epsilon));
to_process.Remove(p);
to_process.Remove(matches_start[0]);
remaining.Remove(matches_start[0]);
bContinue = true;
goto restart_itr;
}
else if (matches_end.Count == 1 && matches_start.Count < 2)
{
remaining.Add(merge_paths(p, matches_end[0], 2 * epsilon));
to_process.Remove(p);
to_process.Remove(matches_end[0]);
remaining.Remove(matches_end[0]);
bContinue = true;
goto restart_itr;
}
else
{
remaining.Add(p);
}
}
to_process.Clear(); to_process.AddRange(remaining); remaining.Clear();
}
c.Paths.AddRange(to_process);
// [TODO] now that we have found all loops, we can chain in dangling curves
c.Paths.AddRange(dangling);
}