Fast hollow sphere generation for PocketMine - Wies

<?php

public function generateHollowSphere($x, $y, $z, $levelName, $radius, $blockId){
    $block = new Block($blockId);
    $level = Server::getInstance()->getLevel($levelName);

    $shape = $this->generateCircle($radius); // generate the main circle

    $this->drawCircle($x, $y, $z, $radius, $block, $level); // Draw the middle circle of the sphere

    for($i=1;$i=<$radius;$i++){
        $hight = $shape[$i];
        $this->draw2CirclesOfSphere($x, $y, $z+$i, $z-$i, $hight, $block, $level);
    }
}

// This is a fast method to draw 2 identical circles
public function draw2CirclesOfSphere($x0, $y0, $z1, $z2, $radius, $block, $level){
    $x = $radius;
    $y = 0;
    $radiusError = 1-$x;

    while($x >= $y){
        $level->setBlock(new Vector3($x + $x0, $y + $y0, $z1), $block, false, false, true);
        $level->setBlock(new Vector3($y + $x0, $x + $y0, $z1), $block, false, false, true);
        $level->setBlock(new Vector3(-$x + $x0, $y + $y0, $z1), $block, false, false, true);
        $level->setBlock(new Vector3(-$y + $x0, $x + $y0, $z1), $block, false, false, true);
        $level->setBlock(new Vector3(-$x + $x0, -$y + $y0, $z1), $block, false, false, true);
        $level->setBlock(new Vector3(-$y + $x0, -$x + $y0, $z1), $block, false, false, true);
        $level->setBlock(new Vector3($x + $x0, -$y + $y0, $z1), $block, false, false, true);
        $level->setBlock(new Vector3($y + $x0, -$x + $y0, $z1), $block, false, false, true);

        $level->setBlock(new Vector3($x + $x0, $y + $y0, $z2), $block, false, false, true);
        $level->setBlock(new Vector3($y + $x0, $x + $y0, $z2), $block, false, false, true);
        $level->setBlock(new Vector3(-$x + $x0, $y + $y0, $z2), $block, false, false, true);
        $level->setBlock(new Vector3(-$y + $x0, $x + $y0, $z2), $block, false, false, true);
        $level->setBlock(new Vector3(-$x + $x0, -$y + $y0, $z2), $block, false, false, true);
        $level->setBlock(new Vector3(-$y + $x0, -$x + $y0, $z2), $block, false, false, true);
        $level->setBlock(new Vector3($x + $x0, -$y + $y0, $z2), $block, false, false, true);
        $level->setBlock(new Vector3($y + $x0, -$x + $y0, $z2), $block, false, false, true);

        $y++;
        if($radiusError<0){
            $radiusError += 2 * $y + 1;
        }else{
            $x--;
            $radiusError+= 2 * ($y - $x + 1);
        }
    }
}

// This is a fast method to draw 1 circle
public function drawCircle($x0, $y0, $z, $radius, $block, $level){
    $x = $radius;
    $y = 0;
    $radiusError = 1-$x;

    while($x >= $y){
        $level->setBlock(new Vector3($x + $x0, $y + $y0, $z), $block, false, false, true);
        $level->setBlock(new Vector3($y + $x0, $x + $y0, $z), $block, false, false, true);
        $level->setBlock(new Vector3(-$x + $x0, $y + $y0, $z), $block, false, false, true);
        $level->setBlock(new Vector3(-$y + $x0, $x + $y0, $z), $block, false, false, true);
        $level->setBlock(new Vector3(-$x + $x0, -$y + $y0, $z), $block, false, false, true);
        $level->setBlock(new Vector3(-$y + $x0, -$x + $y0, $z), $block, false, false, true);
        $level->setBlock(new Vector3($x + $x0, -$y + $y0, $z), $block, false, false, true);
        $level->setBlock(new Vector3($y + $x0, -$x + $y0, $z), $block, false, false, true);

        $y++;
        if($radiusError<0){
            $radiusError += 2 * $y + 1;
        }else{
            $x--;
            $radiusError+= 2 * ($y - $x + 1);
        }
    }
}

// Generates 1/4 of a circle, so from 0 to 1/2 Pi
public function generateCircle($radius){
    $x = $radius;
    $y = 0;
    $radiusError = 1-$x;
    $shape = array();

    while($x >= $y){
        $shape[$x] = $y;
        $shape[$y] = $x;
        $y++;
        if($radiusError<0){
            $radiusError += 2 * $y + 1;
        }else{
            $x--;
            $radiusError+= 2 * ($y - $x + 1);
        }
    }

    return $shape;
}