Setting up a Ground node using SpriteKit? - ios

Question

I've been designing a game where I want the game to stop as soon as the ball makes contact with the ground. My function below is intended to set up the ground.
class GameScene: SKScene, SKPhysicsContactDelegate {
var ground = SKNode()
let groundCategory: UInt32 = 0x1 << 0
let ballCategory: UInt32 = 0x1 << 1
//Generic Anchor coordinate points
let anchorX: CGFloat = 0.5
let anchorY: CGFloat = 0.5
/*Sets the background and ball to be in the correct dimensions*/
override init(size: CGSize) {
super.init(size: size)
//Create the Phyiscs of the game
setUpPhysics()
setUpGround()
setUpBall()
}
func setUpPhysics() -> Void {
self.physicsWorld.gravity = CGVectorMake( 0.0, -5.0 )
self.physicsWorld.contactDelegate = self
}
func setUpGround() -> Void {
self.ground.position = CGPointMake(0, self.frame.size.height)
self.ground.physicsBody = SKPhysicsBody(rectangleOfSize: CGSizeMake(self.frame.size.width, self.frame.size.height)) //Experiment with this
self.ground.physicsBody?.dynamic = false
self.ground.physicsBody?.categoryBitMask = groundCategory //Assigns the bit mask category for ground
self.ball.physicsBody?.contactTestBitMask = ballCategory //Assigns the contacts that we care about for the ground
/*Added in*/
self.ground.physicsBody?.dynamic = true
self.ground.physicsBody?.affectedByGravity = false
self.ground.physicsBody?.allowsRotation = false
/**/
self.addChild(self.ground)
}
func setUpBall() -> Void {
ball.anchorPoint = CGPointMake(anchorX, anchorY)
self.ball.position = CGPointMake(self.frame.size.width/2, self.frame.size.height/2)
self.ball.name = "ball"
self.ball.userInteractionEnabled = false
ball.physicsBody?.usesPreciseCollisionDetection = true
self.ball.physicsBody?.categoryBitMask = ballCategory //Assigns the bit mask category for ball
self.ball.physicsBody?.collisionBitMask = wallCategory | ceilingCategory //Assigns the collisions that the ball can have
self.ball.physicsBody?.contactTestBitMask = groundCategory //Assigns the contacts that we care about for the ball
addChild(self.ball) //Add ball to the display list
}
The problem I am noticing is that when I run the iOS Simulator, the Ground node is not being detected. What am I doing wrong in this case?

Answer 1

Is your ground node not showing up at all? I believe your ground should be an SKSpriteNode. Add that SKSpriteNode as a child of the SKNode object you created.
The SKNode is an empty node and the SKSpriteNode has an actual visual representation. And instead of doing it in a separate function, it would be much simpler if you did it in the DidMoveToView itself.
var objects = SKNode()
addChild(objects)
let ground = SKNode()
ground.position = .......
let colorsprite1 = SKSpriteNode(imageNamed: "yourimageoftheground")
ground.addChild(colorsprite1)
ground.physicsBody?.dynamic = false
Yes you were right to set ground's physics definition as not dynamic. I don't know why people are telling you otherwise. You don't want it to move upon contact with your ball thingies or whatever it is you have moving around in your scene.
Add all other physics definitions you need. Consider using a ContactTestBitMask as you want SpriteKit to let you know when a collision with the ground occurs, instead of SpriteKit handling it by itself. Details about that mask is easily available in StackOverFlow with examples.
objects.addChild(ground)
Hope this helps

Answer 2

Your ballCategory should be assigned to self.ground.contactBitMask not the ball.

Answer 3

You need to set the dynamic property to true in order for contact detection to work.
At the same time, you can set the following properties.
ground.affectedByGravity = false
ground.allowsRotation = false