// Recursively verify that when a rectangle is split into two pieces, the
// centroids of the children sum to give the centroid of the parent.
static void TestCentroidSplitting(S2LatLngRect r, int splits_left)
{
S2LatLngRect child0, child1;
if (S2Testing.Random.OneIn(2))
{
double lat = S2Testing.Random.UniformDouble(r.Lat.Lo, r.Lat.Hi);
child0 = new S2LatLngRect(new R1Interval(r.Lat.Lo, lat), r.Lng);
child1 = new S2LatLngRect(new R1Interval(lat, r.Lat.Hi), r.Lng);
}
else
{
Assert.True(r.Lng.Lo <= r.Lng.Hi);
double lng = S2Testing.Random.UniformDouble(r.Lng.Lo, r.Lng.Hi);
child0 = new S2LatLngRect(r.Lat, new S1Interval(r.Lng.Lo, lng));
child1 = new S2LatLngRect(r.Lat, new S1Interval(lng, r.Lng.Hi));
}
Assert.True((r.Centroid() - child0.Centroid() - child1.Centroid()).Norm() <= 1e-15);
if (splits_left > 0)
{
TestCentroidSplitting(child0, splits_left - 1);
TestCentroidSplitting(child1, splits_left - 1);
}
}
