private static void TestInterpolate(S2Point a, S2Point b, double t, S2Point expected)
{
a = a.Normalize();
b = b.Normalize();
expected = expected.Normalize();
// We allow a bit more than the usual 1e-15 error tolerance because
// interpolation uses trig functions.
S1Angle kError = S1Angle.FromRadians(3e-15);
Assert.True(new S1Angle(S2.Interpolate(a, b, t), expected) <= kError);
// Now test the other interpolation functions.
S1Angle r = t * new S1Angle(a, b);
Assert.True(new S1Angle(S2.GetPointOnLine(a, b, r), expected) <= kError);
if (a.DotProd(b) == 0)
{ // Common in the test cases below.
Assert.True(new S1Angle(S2.GetPointOnRay(a, b, r), expected) <= kError);
}
if (r.Radians >= 0 && r.Radians < 0.99 * S2.M_PI)
{
S1ChordAngle r_ca = new(r);
Assert.True(new S1Angle(S2.GetPointOnLine(a, b, r_ca), expected) <= kError);
if (a.DotProd(b) == 0)
{
Assert.True(new S1Angle(S2.GetPointOnRay(a, b, r_ca), expected) <= kError);
}
}
}