/// <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);
}
public void FindCells()
{
// First we construct "wedges", which are pairs of sequential edges around each vtx.
// we then put all in a hash set, we will iterate until we use up all the available wedges.
// Edges are sorted by positive angle, so they are in clockwise order
// Hence, going from edge n to n+1 is a left-turn, and so "inside" cells are oriented clockwise
int NV = Graph.MaxVertexID;
var wedges = new Index2i[NV][];
var remaining = new HashSet <Index2i>();
foreach (int vid in Graph.VertexIndices())
{
int[] sorted = Graph.SortedVtxEdges(vid);
wedges[vid] = new Index2i[sorted.Length];
for (int k = 0; k < sorted.Length; ++k)
{
wedges[vid][k] = new Index2i(sorted[k], sorted[(k + 1) % sorted.Length]);
remaining.Add(new Index2i(vid, k));
}
}
CellLoops = new List <int[]>();
var loopv = new List <int>();
while (remaining.Count > 0)
{
Index2i idx = remaining.First();
remaining.Remove(idx);
int start_vid = idx.a;
int wid = idx.b;
int e0 = wedges[start_vid][wid].a; e0 = e0 + 1 - 1; // get rid of unused variable warning, want to keep this for debugging
int e1 = wedges[start_vid][wid].b;
loopv.Clear();
loopv.Add(start_vid);
int cur_v = start_vid;
int outgoing_e = e1;
// walk around loop taking immediate left-turns
bool done = false;
while (!done)
{
// find outgoing edge and vtx at far end
Index2i ev = Graph.GetEdgeV(outgoing_e);
int next_v = (ev.a == cur_v) ? ev.b : ev.a;
if (next_v == start_vid)
{
done = true;
continue;
}
// now find wedge at that vtx where this is incoming edge
Index2i[] next_wedges = wedges[next_v];
int use_wedge_idx = -1;
for (int k = 0; k < next_wedges.Length; ++k)
{
if (next_wedges[k].a == outgoing_e)
{
use_wedge_idx = k;
break;
}
}
if (use_wedge_idx == -1)
{
throw new Exception("could not find next wedge?");
}
remaining.Remove(new Index2i(next_v, use_wedge_idx));
loopv.Add(next_v);
cur_v = next_v;
outgoing_e = next_wedges[use_wedge_idx].b;
}
CellLoops.Add(loopv.ToArray());
}
}
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);
}
}
}