TriangleNet.Quality.CheckSeg4Encroach C# (CSharp) Method

CheckSeg4Encroach() public method

Check a subsegment to see if it is encroached; add it to the list if it is.
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.
public CheckSeg4Encroach ( TriangleNet.Data.Osub &testsubseg ) : int
testsubseg TriangleNet.Data.Osub The subsegment to check.
return int
        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;
        }