public function mayIntersect(S2Cell $cell)
{
// If the cap contains any cell vertex, return true.
$vertices = array();
for ($k = 0; $k < 4; ++$k) {
$vertices[$k] = $cell->getVertex($k);
if ($this->contains($vertices[$k])) {
return true;
}
}
return $this->intersects($cell, $vertices);
}
/**
* This test is cheap but is NOT exact. Use Intersects() if you want a more
* accurate and more expensive test. Note that when this method is used by an
* S2RegionCoverer, the accuracy isn't all that important since if a cell may
* intersect the region then it is subdivided, and the accuracy of this method
* goes up as the cells get smaller.
*/
public function mayIntersect(S2Cell $cell)
{
// This test is cheap but is NOT exact (see s2latlngrect.h).
$rb = $cell->getRectBound();
// echo __METHOD__ . $cell . ' ' . $rb . "\n";
return $this->intersects($rb);
}
/**
* Populate the children of "candidate" by expanding the given number of
* levels from the given cell. Returns the number of children that were marked
* "terminal".
*/
private function expandChildren(Candidate $candidate, S2Cell $cell, $numLevels)
{
$numLevels--;
$childCells = array();
for ($i = 0; $i < 4; ++$i) {
$childCells[$i] = new S2Cell();
}
$cell->subdivide($childCells);
$numTerminals = 0;
for ($i = 0; $i < 4; ++$i) {
if ($numLevels > 0) {
if ($this->region->mayIntersect($childCells[$i])) {
$numTerminals += $this->expandChildren($candidate, $childCells[$i], $numLevels);
}
continue;
}
$child = $this->newCandidate($childCells[$i]);
// echo "child for " . $childCells[$i] . " is " . $child . "\n";
if ($child != null) {
$candidate->children[$candidate->numChildren++] = $child;
if ($child->isTerminal) {
++$numTerminals;
}
}
}
return $numTerminals;
}
