bool CheckTraversal(float2 a, float2 b, float2 c, Edge *exit, bool lhs, out Disturbance disturbance)
{
if (!Math.ProjectSeg(a, c, b, out var bac))
{
disturbance = default;
return(false);
}
var mirror = b + (c - 2 * bac + a);
var lba = math.lengthsq(a - b);
var lbc = math.lengthsq(c - b);
var clearance = math.sqrt(math.min(lba, lbc));
var constraint = TryGetConstraint(exit, clearance, b, mirror, lhs);
if (constraint == null || constraint->RefineFailed)
{
disturbance = default;
return(false);
}
var s1 = constraint->Org->Point;
var s2 = constraint->Dest->Point;
if (!Math.ProjectSeg(s1, s2, b, out var bi))
{
disturbance = default;
return(false);
}
// The paper says R is delimited by a line parallel to s passing by b.
// When cl(a, b, c) == dist(b, a) and dist(b, a) < dist(b, s) this allows
// for vertices in R violating definition 3.4: dist(v, s) < cl(a, b, c).
// R will be delimited by a line parallel to s at a distance of cl(a, b, c)
// Technially r1 should be at the intersection point with bc, but as bc
// is enclosed by the Delaunay circle of triangle abc this is irrelevant.
// R is triangle r1, r2, c
var bib = b - bi;
var lbib = math.length(bib);
clearance = math.min(clearance, lbib);
var r1 = bi + bib / lbib * clearance;
var acp = Math.PerpCw(c - a);
var s12 = s2 - s1;
var s12p = Math.PerpCw(s12);
var r2 = Math.Angle(acp, s12p) < 0
? Math.IntersectLineLine(r1, r1 + s12, c, c + acp)
: Math.IntersectLineLine(r1, r1 + s12, c, c + s12p);
if (TryGetDisturbance(lhs ? exit->Sym : exit, r1, r2, c, out var e, out var u, out var vert, lhs))
{
var v = vert->Point;
var vi = Math.ProjectLine(s1, s2, v);
var lvs = math.length(vi - v);
var lve = math.length(e - v);
if (lvs < lve && lvs < clearance)
{
Math.CircleFromPoints(u, v, e, out var centre, out var radius);
var t = Math.IntersectLineCircle(s1, s2, centre, radius, out var x1, out var x2);
Assert.IsTrue(t == 2);
var pRef = (x1 + x2) / 2;
if (ValidateRefinement(ref pRef, constraint))
{
disturbance = new Disturbance(vert, pRef, constraint);
return(true);
}
constraint->RefineFailed = true;
}
}
disturbance = default;
return(false);
}
