private function getLongitude($i, $j)
{
$p = S2Projections::faceUvToXyz($this->face, $this->uv[0][$i], $this->uv[1][$j]);
return atan2($p->y, $p->x);
}
/**
* Given (i, j) coordinates that may be out of bounds, normalize them by
* returning the corresponding neighbor cell on an adjacent face.
*/
private static function fromFaceIJWrap($face, $i, $j)
{
// Convert i and j to the coordinates of a leaf cell just beyond the
// boundary of this face. This prevents 32-bit overflow in the case
// of finding the neighbors of a face cell, and also means that we
// don't need to worry about the distinction between (s,t) and (u,v).
$i = max(-1, min(self::MAX_SIZE, $i));
$j = max(-1, min(self::MAX_SIZE, $j));
// Find the (s,t) coordinates corresponding to (i,j). At least one
// of these coordinates will be just outside the range [0, 1].
$kScale = 1.0 / self::MAX_SIZE;
$s = $kScale * (($i << 1) + 1 - self::MAX_SIZE);
$t = $kScale * (($j << 1) + 1 - self::MAX_SIZE);
// Find the leaf cell coordinates on the adjacent face, and convert
// them to a cell id at the appropriate level.
$p = S2Projections::faceUvToXyz($face, $s, $t);
$face = S2Projections::xyzToFace($p);
$st = S2Projections::validFaceXyzToUv($face, $p);
return self::fromFaceIJ($face, self::stToIJ($st->x()), self::stToIJ($st->y()));
}
/** Computes a set of initial candidates that cover the given region. */
private function getInitialCandidates()
{
// Optimization: if at least 4 cells are desired (the normal case),
// start with a 4-cell covering of the region's bounding cap. This
// lets us skip quite a few levels of refinement when the region to
// be covered is relatively small.
if ($this->maxCells >= 4) {
// Find the maximum level such that the bounding cap contains at most one
// cell vertex at that level.
$cap = $this->region->getCapBound();
$level = min(S2Projections::MIN_WIDTH()->getMaxLevel(2 * $cap->angle()->radians()), min($this->maxLevel(), S2CellId::MAX_LEVEL - 1));
if ($this->levelMod() > 1 && $level > $this->minLevel()) {
$level -= ($level - $this->minLevel()) % $this->levelMod();
}
// We don't bother trying to optimize the level == 0 case, since more than
// four face cells may be required.
if ($level > 0) {
// Find the leaf cell containing the cap axis, and determine which
// subcell of the parent cell contains it.
/** @var S2CellId[] $base */
$base = array();
$s2point_tmp = $cap->axis();
$id = S2CellId::fromPoint($s2point_tmp);
$id->getVertexNeighbors($level, $base);
for ($i = 0; $i < count($base); ++$i) {
// printf("(face=%s pos=%s level=%s)\n", $base[$i]->face(), dechex($base[$i]->pos()), $base[$i]->level());
// echo "new S2Cell(base[i])\n";
$cell = new S2Cell($base[$i]);
// echo "neighbour cell: " . $cell . "\n";
$c = $this->newCandidate($cell);
// if ($c !== null)
// echo "addCandidato getInitialCandidates: " . $c->cell->id() . "\n";
$this->addCandidate($c);
}
// echo "\n\n\n";
return;
}
}
// Default: start with all six cube faces.
$face_cells = self::FACE_CELLS();
for ($face = 0; $face < 6; ++$face) {
$c = $this->newCandidate($face_cells[$face]);
echo "addCandidato getInitialCandidates_default: " . $c->cell->id() . "\n";
$this->addCandidate($c);
}
}