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);
 }