SpriteKit - Create at random position without overlapping - swift

Question

I want to create some sprites at random positions without getting overlapped, here is my code :
var sprites = [SKSpriteNode]()
for index in 0...spriteArray {
let sprite = SKSpriteNode(imageNamed: named)
sprites.append(sprite)
checkInterception(sprite, sprite2: sprites)// positioning using a function
addChild(sprite)
}
Here I check for overlapping:
func checkInterception(sprite1: SKSpriteNode, sprite2: [SKSpriteNode]) {
let xPos = CGFloat( Float(arc4random()) / Float(UINT32_MAX)) * maxX
let yPos = CGFloat( Float(arc4random()) / Float(UINT32_MAX)) * maxY
sprite1.position = CGPoint(x: xPos, y: yPos )
for index in 0...sprite2.count-1 {
if sprite1.intersectsNode(sprite2[index]) {
let yPos = sprite1.position.y + sprite1.size.height
sprite1.position = CGPoint(x: xPos, y: yPos )
}
}
}
But some sprites still get overlapped. I know there is something not right with the for loop, but just can't figure it out.

Answer 1

I am sure there are a few different ways to attack the problem and this would be the closest to what you already wrote.
let sprites = [SKSpriteNode]() //loaded with your sprites to spawn
let maxX = size.width //whatever your max is
let maxY = size.height //whatever your max is
var spritesAdded = [SKSpriteNode]()
for currentSprite in sprites{
addChild(currentSprite)
var intersects = true
while (intersects){
let xPos = CGFloat( Float(arc4random()) / Float(UINT32_MAX)) * maxX
let yPos = CGFloat( Float(arc4random()) / Float(UINT32_MAX)) * maxY
currentSprite.position = CGPoint(x: xPos, y: yPos )
intersects = false
for sprite in spritesAdded{
if (currentSprite.intersectsNode(sprite)){
intersects = true
break
}
}
}
spritesAdded.append(currentSprite)
}
Things to consider is if you don't already know where it is safe to add a sprite you run the risk of performance. For instance adding your last sprite may take 1,000,000 attempts before it randomly picks a point that doesn't intersect with others.
If you don't have to have them all added at once I would attack the problem on the update loop and do something like this...
var sprites = [SKSpriteNode]() //loaded with your sprites to spawn
var maxX : CGFloat = 0.0 //whatever your max is
var maxY : CGFloat = 0.0 //whatever your max is
var spritesAdded = [SKSpriteNode]()
override func didMoveToView(view: SKView) {
maxX = size.width //whatever your max is
maxY = size.height //whatever your max is
}
func addSprite(){
if let currentSprite = sprites.first {
let xPos = CGFloat( Float(arc4random()) / Float(UINT32_MAX)) * maxX
let yPos = CGFloat( Float(arc4random()) / Float(UINT32_MAX)) * maxY
currentSprite.position = CGPoint(x: xPos, y: yPos )
for sprite in spritesAdded{
if (currentSprite.intersectsNode(sprite)){
return
}
}
addChild(currentSprite)
spritesAdded.append(currentSprite)
sprites.removeFirst()
}
}
override func update(currentTime: NSTimeInterval) {
addSprite()
}
Kind of rough but the idea is every update it will try to add a sprite. This way if you run out of room it won't lock up. Hopefully that helps.