public List <Segment2d> TrimSegment2d(Segment2d seg)
{
// Find points where the outer boundary and holes intersect the segment.
var intersectionPoints = new List <Vector2d>();
intersectionPoints.AddRange(outer.FindIntersections(seg));
foreach (var hole in holes)
{
intersectionPoints.AddRange(hole.FindIntersections(seg));
}
// Handle the case where segment is fully contained
if (intersectionPoints.Count == 0)
{
if (Contains(seg))
{
return new List <Segment2d>()
{
new Segment2d(seg)
}
}
}
;
// Add segment start & end points in case they lay within the polygon
intersectionPoints.Add(seg.P0);
intersectionPoints.Add(seg.P1);
// Sort the points by their distance along the segment.
var intersections = new List <Tuple <double, Vector2d> >();
var line = new Line2d(seg.Center, seg.Direction);
foreach (var point in intersectionPoints)
{
intersections.Add(Tuple.Create(line.Project(point), point));
}
intersections.Sort((a, b) => a.Item1.CompareTo(b.Item1));
// Add any segment with non-zero length that is contained in the polygon
var containedSegments = new List <Segment2d>();
for (int i = 1; i < intersections.Count; ++i)
{
var potentialSegment = new Segment2d(intersections[i - 1].Item2, intersections[i].Item2);
if (potentialSegment.Length <= MathUtil.Epsilon)
{
continue;
}
if (Contains(potentialSegment.Center))
{
containedSegments.Add(potentialSegment);
}
}
return(containedSegments);
}
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);
}
}
}
