/// <summary>
/// Check if given triangle is blinded by given segment.
/// </summary>
/// <param name="tri">Triangle.</param>
/// <param name="seg">Segments</param>
/// <returns>Returns true, if the triangle is blinded.</returns>
private bool TriangleIsBlinded(ref Otri tri, ref Osub seg)
{
Point c, pt;
Vertex torg = tri.Org();
Vertex tdest = tri.Dest();
Vertex tapex = tri.Apex();
Vertex sorg = seg.Org();
Vertex sdest = seg.Dest();
c = this.points[tri.triangle.id];
if (SegmentsIntersect(sorg, sdest, c, torg, out pt, true))
{
return true;
}
if (SegmentsIntersect(sorg, sdest, c, tdest, out pt, true))
{
return true;
}
if (SegmentsIntersect(sorg, sdest, c, tapex, out pt, true))
{
return true;
}
return false;
}
/// <summary>
/// Check a subsegment to see if it is encroached; add it to the list if it is.
/// </summary>
/// <param name="testsubseg">The subsegment to check.</param>
/// <returns>Returns a nonzero value if the subsegment is encroached.</returns>
/// <remarks>
/// A subsegment is encroached if there is a vertex in its diametral lens.
/// For Ruppert's algorithm (-D switch), the "diametral lens" is the
/// diametral circle. For Chew's algorithm (default), the diametral lens is
/// just big enough to enclose two isosceles triangles whose bases are the
/// subsegment. Each of the two isosceles triangles has two angles equal
/// to 'b.minangle'.
///
/// Chew's algorithm does not require diametral lenses at all--but they save
/// time. Any vertex inside a subsegment's diametral lens implies that the
/// triangle adjoining the subsegment will be too skinny, so it's only a
/// matter of time before the encroaching vertex is deleted by Chew's
/// algorithm. It's faster to simply not insert the doomed vertex in the
/// first place, which is why I use diametral lenses with Chew's algorithm.
/// </remarks>
public int CheckSeg4Encroach(ref Osub testsubseg)
{
Otri neighbortri = default(Otri);
Osub testsym = default(Osub);
BadSubseg encroachedseg;
double dotproduct;
int encroached;
int sides;
Vertex eorg, edest, eapex;
encroached = 0;
sides = 0;
eorg = testsubseg.Org();
edest = testsubseg.Dest();
// Check one neighbor of the subsegment.
testsubseg.TriPivot(ref neighbortri);
// Does the neighbor exist, or is this a boundary edge?
if (neighbortri.triangle != Mesh.dummytri)
{
sides++;
// Find a vertex opposite this subsegment.
eapex = neighbortri.Apex();
// Check whether the apex is in the diametral lens of the subsegment
// (the diametral circle if 'conformdel' is set). A dot product
// of two sides of the triangle is used to check whether the angle
// at the apex is greater than (180 - 2 'minangle') degrees (for
// lenses; 90 degrees for diametral circles).
dotproduct = (eorg.x - eapex.x) * (edest.x - eapex.x) +
(eorg.y - eapex.y) * (edest.y - eapex.y);
if (dotproduct < 0.0)
{
if (behavior.ConformingDelaunay ||
(dotproduct * dotproduct >=
(2.0 * behavior.goodAngle - 1.0) * (2.0 * behavior.goodAngle - 1.0) *
((eorg.x - eapex.x) * (eorg.x - eapex.x) +
(eorg.y - eapex.y) * (eorg.y - eapex.y)) *
((edest.x - eapex.x) * (edest.x - eapex.x) +
(edest.y - eapex.y) * (edest.y - eapex.y))))
{
encroached = 1;
}
}
}
// Check the other neighbor of the subsegment.
testsubseg.Sym(ref testsym);
testsym.TriPivot(ref neighbortri);
// Does the neighbor exist, or is this a boundary edge?
if (neighbortri.triangle != Mesh.dummytri)
{
sides++;
// Find the other vertex opposite this subsegment.
eapex = neighbortri.Apex();
// Check whether the apex is in the diametral lens of the subsegment
// (or the diametral circle, if 'conformdel' is set).
dotproduct = (eorg.x - eapex.x) * (edest.x - eapex.x) +
(eorg.y - eapex.y) * (edest.y - eapex.y);
if (dotproduct < 0.0)
{
if (behavior.ConformingDelaunay ||
(dotproduct * dotproduct >=
(2.0 * behavior.goodAngle - 1.0) * (2.0 * behavior.goodAngle - 1.0) *
((eorg.x - eapex.x) * (eorg.x - eapex.x) +
(eorg.y - eapex.y) * (eorg.y - eapex.y)) *
((edest.x - eapex.x) * (edest.x - eapex.x) +
(edest.y - eapex.y) * (edest.y - eapex.y))))
{
encroached += 2;
}
}
}
if (encroached > 0 && (behavior.NoBisect == 0 || ((behavior.NoBisect == 1) && (sides == 2))))
{
// Add the subsegment to the list of encroached subsegments.
// Be sure to get the orientation right.
encroachedseg = new BadSubseg();
if (encroached == 1)
{
encroachedseg.encsubseg = testsubseg;
encroachedseg.subsegorg = eorg;
encroachedseg.subsegdest = edest;
}
else
{
encroachedseg.encsubseg = testsym;
encroachedseg.subsegorg = edest;
encroachedseg.subsegdest = eorg;
}
badsubsegs.Enqueue(encroachedseg);
}
return encroached;
}