/// <summary>
/// Find and remove any junction (ie valence>2) vertices of the graph.
/// At a junction, the pair of best-aligned (ie straightest) edges are left
/// connected, and all the other edges are disconnected
///
/// [TODO] currently there is no DGraph2.SetEdge(), so the 'other' edges
/// are deleted and new edges inserted. Hence, edge IDs are not preserved.
/// </summary>
public static int DisconnectJunctions(DGraph2 graph)
{
var junctions = new List <int>();
// find all junctions
foreach (int vid in graph.VertexIndices())
{
if (graph.IsJunctionVertex(vid))
{
junctions.Add(vid);
}
}
foreach (int vid in junctions)
{
Vector2d v = graph.GetVertex(vid);
int[] nbr_verts = graph.VtxVerticesItr(vid).ToArray();
// find best-aligned pair of edges connected to vid
Index2i best_aligned = Index2i.Max; double max_angle = 0;
for (int i = 0; i < nbr_verts.Length; ++i)
{
for (int j = i + 1; j < nbr_verts.Length; ++j)
{
double angle = Vector2d.AngleD(
(graph.GetVertex(nbr_verts[i]) - v).Normalized,
(graph.GetVertex(nbr_verts[j]) - v).Normalized);
angle = Math.Abs(angle);
if (angle > max_angle)
{
max_angle = angle;
best_aligned = new Index2i(nbr_verts[i], nbr_verts[j]);
}
}
}
// for nbr verts that are not part of the best_aligned edges,
// we remove those edges and add a new one connected to a new vertex
for (int k = 0; k < nbr_verts.Length; ++k)
{
if (nbr_verts[k] == best_aligned.a || nbr_verts[k] == best_aligned.b)
{
continue;
}
int eid = graph.FindEdge(vid, nbr_verts[k]);
graph.RemoveEdge(eid, true);
if (graph.IsVertex(nbr_verts[k]))
{
var newpos = Vector2d.Lerp(graph.GetVertex(nbr_verts[k]), v, 0.99);
int newv = graph.AppendVertex(newpos);
graph.AppendEdge(nbr_verts[k], newv);
}
}
}
return(junctions.Count);
}
/// <summary>
/// compute length of path through graph
/// </summary>
public static double PathLength(DGraph2 graph, IList <int> pathVertices)
{
double len = 0;
int N = pathVertices.Count;
Vector2d prev = graph.GetVertex(pathVertices[0]), next = Vector2d.Zero;
for (int i = 1; i < N; ++i)
{
next = graph.GetVertex(pathVertices[i]);
len += prev.Distance(next);
prev = next;
}
return(len);
}
/// <summary>
/// foreach edge [vid,b] connected to junction vertex vid, remove, add new vertex c,
/// and then add new edge [b,c]. Optionally move c a bit back along edge from vid.
/// </summary>
public static void DisconnectJunction(DGraph2 graph, int vid, double shrinkFactor = 1.0)
{
Vector2d v = graph.GetVertex(vid);
int[] nbr_verts = graph.VtxVerticesItr(vid).ToArray();
for (int k = 0; k < nbr_verts.Length; ++k)
{
int eid = graph.FindEdge(vid, nbr_verts[k]);
graph.RemoveEdge(eid, true);
if (graph.IsVertex(nbr_verts[k]))
{
Vector2d newpos = Vector2d.Lerp(graph.GetVertex(nbr_verts[k]), v, shrinkFactor);
int newv = graph.AppendVertex(newpos);
graph.AppendEdge(nbr_verts[k], newv);
}
}
}
/// <summary>
/// If vid has two or more neighbours, returns uniform laplacian, otherwise returns vid position
/// </summary>
public static Vector2d VertexLaplacian(DGraph2 graph, int vid, out bool isValid)
{
Vector2d v = graph.GetVertex(vid);
Vector2d centroid = Vector2d.Zero;
int n = 0;
foreach (int vnbr in graph.VtxVerticesItr(vid))
{
centroid += graph.GetVertex(vnbr);
n++;
}
if (n == 2)
{
centroid /= n;
isValid = true;
return(centroid - v);
}
isValid = false;
return(v);
}
public void SplitToMaxEdgeLength(double fMaxLen)
{
var queue = new List <int>();
int NE = Graph.MaxEdgeID;
for (int eid = 0; eid < NE; ++eid)
{
if (!Graph.IsEdge(eid))
{
continue;
}
if (FixedEdgeFilterF(eid))
{
continue;
}
Index2i ev = Graph.GetEdgeV(eid);
double dist = Graph.GetVertex(ev.a).Distance(Graph.GetVertex(ev.b));
if (dist > fMaxLen)
{
DGraph2.EdgeSplitInfo splitInfo;
if (Graph.SplitEdge(eid, out splitInfo) == MeshResult.Ok && dist > 2 * fMaxLen)
{
queue.Add(eid);
queue.Add(splitInfo.eNewBN);
}
}
}
while (queue.Count > 0)
{
int eid = queue[queue.Count - 1];
queue.RemoveAt(queue.Count - 1);
if (!Graph.IsEdge(eid))
{
continue;
}
Index2i ev = Graph.GetEdgeV(eid);
double dist = Graph.GetVertex(ev.a).Distance(Graph.GetVertex(ev.b));
if (dist > fMaxLen)
{
DGraph2.EdgeSplitInfo splitInfo;
if (Graph.SplitEdge(eid, out splitInfo) == MeshResult.Ok && dist > 2 * fMaxLen)
{
queue.Add(eid);
queue.Add(splitInfo.eNewBN);
}
}
}
}
private static int MergeAppendVertex(DGraph2 graph, Vector2d vertex, double mergeThreshold)
{
for (int i = 0; i < graph.VertexCount; i++)
{
double d = vertex.Distance(graph.GetVertex(i));
if (d < mergeThreshold)
{
return(i);
}
}
return(graph.AppendVertex(vertex));
}
public void AppendGraph(DGraph2 graph, int gid = -1)
{
int[] mapV = new int[graph.MaxVertexID];
foreach (int vid in graph.VertexIndices())
{
mapV[vid] = this.AppendVertex(graph.GetVertex(vid));
}
foreach (int eid in graph.EdgeIndices())
{
Index2i ev = graph.GetEdgeV(eid);
int use_gid = (gid == -1) ? graph.GetEdgeGroup(eid) : gid;
this.AppendEdge(mapV[ev.a], mapV[ev.b], use_gid);
}
}
/*
* Graph improvement
*/
/// <summary>
/// connect open boundary vertices within distThresh, by inserting new segments
/// </summary>
public void ConnectOpenBoundaries(double distThresh)
{
int max_vid = Graph.MaxVertexID;
for (int vid = 0; vid < max_vid; ++vid)
{
if (Graph.IsBoundaryVertex(vid) == false)
{
continue;
}
Vector2d v = Graph.GetVertex(vid);
int snap_with = find_nearest_boundary_vertex(v, distThresh, vid);
if (snap_with != -1)
{
Vector2d v2 = Graph.GetVertex(snap_with);
Insert(v, v2);
}
}
}
/// <summary>
/// Convert cells to polygons, with optional filter.
/// If filter returns false, polygon is not included in output
/// </summary>
public List <Polygon2d> CellsToPolygons(Func <Polygon2d, bool> FilterF = null)
{
var result = new List <Polygon2d>();
for (int i = 0; i < CellLoops.Count; ++i)
{
int[] loop = CellLoops[i];
var poly = new Polygon2d();
for (int k = 0; k < loop.Length; ++k)
{
poly.AppendVertex(Graph.GetVertex(loop[k]));
}
if (FilterF != null && FilterF(poly) == false)
{
continue;
}
result.Add(poly);
}
return(result);
}
/// <summary>
/// Decompose graph into simple polylines and polygons.
/// </summary>
public static Curves ExtractCurves(DGraph2 graph)
{
Curves c = new Curves();
c.Loops = new List <Polygon2d>();
c.Paths = new List <PolyLine2d>();
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));
while (true)
{
used.Add(eid);
Index2i next = NextEdgeAndVtx(eid, vid, graph);
eid = next.a;
vid = next.b;
path.AppendVertex(graph.GetVertex(vid));
if (eid == int.MaxValue || junctions.Contains(vid))
{
break; // done!
}
}
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);
}
protected virtual void do_split(Line2d line, bool insert_edges, int insert_gid)
{
if (EdgeSigns.Length < Graph.MaxVertexID)
{
EdgeSigns.resize(Graph.MaxVertexID);
}
foreach (int vid in Graph.VertexIndices())
{
EdgeSigns[vid] = line.WhichSide(Graph.GetVertex(vid), OnVertexTol);
}
hits.Clear();
foreach (int eid in Graph.EdgeIndices())
{
Index2i ev = Graph.GetEdgeV(eid);
var signs = new Index2i(EdgeSigns[ev.a], EdgeSigns[ev.b]);
if (signs.a * signs.b > 0)
{
continue; // both positive or negative, ignore
}
var hit = new edge_hit()
{
hit_eid = eid, vtx_signs = signs, hit_vid = -1
};
Vector2d a = Graph.GetVertex(ev.a);
Vector2d b = Graph.GetVertex(ev.b);
// parallel-edge case (both are zero)
if (signs.a == signs.b)
{
if (a.DistanceSquared(b) > MathUtil.Epsilon)
{
// we need to somehow not insert a new segment for this span below.
// so, insert two hit points for the ray-interval, with same eid.
// This will result in this span being skipped by the same-eid test below
// *however*, if other edges self-intersect w/ this segment, this will *not work*
// and duplicate edges will be inserted
hit.hit_vid = ev.a;
hit.line_t = line.Project(a);
hits.Add(hit);
hit.hit_vid = ev.b;
hit.line_t = line.Project(b);
hits.Add(hit);
}
else
{
// degenerate edge - fall through to a == 0 case below
signs.b = 1;
}
}
if (signs.a == 0)
{
hit.hit_pos = a;
hit.hit_vid = ev.a;
hit.line_t = line.Project(a);
}
else if (signs.b == 0)
{
hit.hit_pos = b;
hit.hit_vid = ev.b;
hit.line_t = line.Project(b);
}
else
{
var intr = new IntrLine2Segment2(line, new Segment2d(a, b));
if (intr.Find() == false)
{
throw new Exception("GraphSplitter2d.Split: signs are different but ray did not it?");
}
if (intr.IsSimpleIntersection)
{
hit.hit_pos = intr.Point;
hit.line_t = intr.Parameter;
}
else
{
throw new Exception("GraphSplitter2d.Split: got parallel edge case!");
}
}
hits.Add(hit);
}
// sort by increasing ray-t
hits.Sort((hit0, hit1) => { return(hit0.line_t.CompareTo(hit1.line_t)); });
// insert segments between successive intersection points
int N = hits.Count;
for (int i = 0; i < N - 1; ++i)
{
int j = i + 1;
// note: skipping parallel segments depends on this eid == eid test (see above)
if (hits[i].line_t == hits[j].line_t || hits[i].hit_eid == hits[j].hit_eid)
{
continue;
}
int vi = hits[i].hit_vid;
int vj = hits[j].hit_vid;
if (vi == vj && vi >= 0)
{
continue;
}
if (vi >= 0 && vj >= 0)
{
int existing = Graph.FindEdge(vi, vj);
if (existing >= 0)
{
continue;
}
}
if (vi == -1)
{
DGraph2.EdgeSplitInfo split;
var result = Graph.SplitEdge(hits[i].hit_eid, out split);
if (result != MeshResult.Ok)
{
throw new Exception("GraphSplitter2d.Split: first edge split failed!");
}
vi = split.vNew;
Graph.SetVertex(vi, hits[i].hit_pos);
edge_hit tmp = hits[i]; tmp.hit_vid = vi; hits[i] = tmp;
}
if (vj == -1)
{
DGraph2.EdgeSplitInfo split;
var result = Graph.SplitEdge(hits[j].hit_eid, out split);
if (result != MeshResult.Ok)
{
throw new Exception("GraphSplitter2d.Split: second edge split failed!");
}
vj = split.vNew;
Graph.SetVertex(vj, hits[j].hit_pos);
edge_hit tmp = hits[j]; tmp.hit_vid = vj; hits[j] = tmp;
}
// check if we actually want to add this segment
if (InsideTestF != null)
{
Vector2d midpoint = 0.5 * (Graph.GetVertex(vi) + Graph.GetVertex(vj));
if (InsideTestF(midpoint) == false)
{
continue;
}
}
if (insert_edges)
{
Graph.AppendEdge(vi, vj, insert_gid);
}
}
}