private double[] Line_IntersectionsWithSegment(Double2 v1, Double2 v2)
{
var k = (v2 - v1).Cross(B - A);
if (DoubleUtils.RoughlyZeroSquared(k))
{
return(new double[0]);
}
return(new[] { (v2 - v1).Cross(v1 - A) / k });
}
// Generate a curve coordinate extrapolator
private static Func <Double2, Double4> CoordExtrapolator(CurveVertex[] vertices)
{
// Check for the length
int vl = vertices.Length;
if (vl == 1)
{
var v = vertices[0].CurveCoords;
return(x => v);
}
// Extrapolate along the line
else if (vl == 2)
{
var va = vertices[0];
var vb = vertices[1];
var dx = vb.Position - va.Position;
return(delegate(Double2 x)
{
var t = (x - va.Position).Dot(dx) / dx.LengthSquared;
return va.CurveCoords + t * (vb.CurveCoords - va.CurveCoords);
});
}
// Extrapolate along a triangle
else
{
// Choose a nonzero-area triangle
int i = 0, ik = 1, ik2 = 2;
for (; i < vl; i++)
{
ik = (i + 1) % vl;
ik2 = (i + 2) % vl;
var winding = vertices[i].Position.Cross(vertices[ik].Position)
+ vertices[ik].Position.Cross(vertices[ik2].Position)
+ vertices[ik2].Position.Cross(vertices[i].Position);
if (!DoubleUtils.RoughlyZeroSquared(winding))
{
break;
}
}
// If there is no nonzero-area triangle, choose the most distant vertices and pick their extrapolator
if (i == vl)
{
var imin = 0;
var imax = 0;
for (i = 1; i < vl; i++)
{
if (vertices[imin].Position.X > vertices[i].Position.X)
{
imin = i;
}
if (vertices[imax].Position.X < vertices[i].Position.X)
{
imax = i;
}
}
return(CoordExtrapolator(new[] { vertices[imin], vertices[imax] }));
}
var a = vertices[i].Position;
var dv1 = vertices[ik].Position - a;
var dv2 = vertices[ik2].Position - a;
var k = dv1.Cross(dv2);
var ta = vertices[i].CurveCoords;
var tb = vertices[ik].CurveCoords;
var tc = vertices[ik2].CurveCoords;
return(delegate(Double2 x)
{
var u = (x - a).Cross(dv2) / k;
var v = -(x - a).Cross(dv1) / k;
return ta + u * (tb - ta) + v * (tc - ta);
});
}
}
