function &sphereScene($level, &$center, $radius)
{
$sphere = new Sphere($center, $radius);
if ($level == 1) {
return $sphere;
} else {
$scene = new Group(new Sphere($center, 3.0 * $radius));
$scene->add($sphere);
$rn = 3.0 * $radius / sqrt(12.0);
for ($dz = -1; $dz <= 1; $dz += 2) {
for ($dx = -1; $dx <= 1; $dx += 2) {
$c2 = newVector($center[0] - $dx * $rn, $center[1] + $rn, $center[2] - $dz * $rn);
$scene->add(Scene::sphereScene($level - 1, $c2, $radius / 2.0));
}
}
return $scene;
}
}
