public function addNode($x, $y)
{
$node = new EdgeNode();
$node->getVertex()->setX($x);
$node->getVertex()->setY($y);
$this->mList[] = $node;
}
/**
* @param StNode $st
* @param ItNodeTable $it
* @param EdgeNode $edge
* @param float $dy
*
* @returns StNode
*/
private function addStEdge($st, $it, $edge, $dy)
{
if ($st === null) {
/* Append edge onto the tail end of the ST */
$st = new StNode($edge, null);
} else {
$den = $st->getXt() - $st->getXb() - ($edge->getXt() - $edge->getXb());
/* If new edge and ST edge don't cross */
if ($edge->getXt() >= $st->getXt() || $edge->getDx() === $st->getDx() || abs($den) <= self::EPSILON) {
/* No intersection - insert edge here (before the ST edge) */
$existingNode = $st;
$st = new StNode($edge, $existingNode);
} else {
/* Compute intersection between new edge and ST edge */
$r = ($edge->getXb() - $st->getXb()) / $den;
$x = $st->getXb() + $r * ($st->getXt() - $st->getXb());
$y = $r * $dy;
/* Insert the edge pointers and the intersection point in the IT */
$it->setTopNode($this->addIntersection($it->getTopNode(), $st->getEdge(), $edge, $x, $y));
/* Head further into the ST */
$st->setPrev($this->addStEdge($st->getPrev(), $it, $edge, $dy));
}
}
return $st;
}
