public static function xyzToFace(S2Point $p)
{
$face = $p->largestAbsComponent();
if ($p->get($face) < 0) {
$face += 3;
}
return $face;
}
public static function longitude(S2Point $p)
{
// Note that atan2(0, 0) is defined to be zero.
return S1Angle::sradians(atan2($p->get(1), $p->get(0)));
}