// Checks that the error returned by S2EdgeDistances.GetUpdateMinDistanceMaxError() for
// the distance "input" (measured in radians) corresponds to a distance error
// of less than "max_error" (measured in radians).
//
// The reason for the awkward phraseology above is that the value returned by
// GetUpdateMinDistanceMaxError() is not a distance; it represents an error in
// the *squared* distance.
private static void CheckUpdateMinDistanceMaxError(double actual, double max_error)
{
S1ChordAngle ca = new(S1Angle.FromRadians(actual));
S1Angle bound = ca.PlusError(S2.GetUpdateMinDistanceMaxError(ca)).ToAngle();
Assert.True(bound.Radians - actual <= max_error);
}
public void Test_S2_GetUpdateMinInteriorDistanceMaxError()
{
// Check that the error bound returned by
// GetUpdateMinInteriorDistanceMaxError() is large enough.
for (int iter = 0; iter < 10000; ++iter)
{
S2Point a0 = S2Testing.RandomPoint();
var lenRadians = Math.PI * Math.Pow(1e-20, S2Testing.Random.RandDouble());
S1Angle len = S1Angle.FromRadians(lenRadians);
if (S2Testing.Random.OneIn(4))
{
len = S1Angle.FromRadians(S2.M_PI) - len;
}
S2Point a1 = S2.GetPointOnLine(a0, S2Testing.RandomPoint(), len);
// TODO(ericv): The error bound holds for antipodal points, but the S2
// predicates used to test the error do not support antipodal points yet.
if (a1 == -a0)
{
continue;
}
S2Point n = S2.RobustCrossProd(a0, a1).Normalize();
double f = Math.Pow(1e-20, S2Testing.Random.RandDouble());
S2Point a = ((1 - f) * a0 + f * a1).Normalize();
var rRadians = S2.M_PI_2 * Math.Pow(1e-20, S2Testing.Random.RandDouble());
S1Angle r = S1Angle.FromRadians(rRadians);
if (S2Testing.Random.OneIn(2))
{
r = S1Angle.FromRadians(S2.M_PI_2) - r;
}
S2Point x = S2.GetPointOnLine(a, n, r);
S1ChordAngle min_dist = S1ChordAngle.Infinity;
if (!S2.UpdateMinInteriorDistance(x, a0, a1, ref min_dist))
{
--iter; continue;
}
double error = S2.GetUpdateMinDistanceMaxError(min_dist);
Assert.True(S2Pred.CompareEdgeDistance(x, a0, a1, min_dist.PlusError(error)) <= 0);
Assert.True(S2Pred.CompareEdgeDistance(x, a0, a1, min_dist.PlusError(-error)) >= 0);
}
}
