Confirming some results with iOS26 (sim), macOS26 and Xcode26.
The field drawing is offset unless the scene anchorPoint is zero.
However, field visualisations are showing for me with a radialGravity and four linearGravity (mimicing particles bouncing off walls).
//: A SpriteKit based Playground
import PlaygroundSupport
import SpriteKit
let sqSize = CGSize(width: 50, height: 50)
let smallParticles = CGSize(width: 4, height: 4)
class GameScene: SKScene {
var field: SKFieldNode!
var em1: SKEmitterNode!
var em2: SKEmitterNode!
var em2Mask: UInt32 = 2 // initially off, variable used so touches can toggle
let field1Mask: UInt32 = 0b0001
let bottomWallMask: UInt32 = 0b0100
let wallGravityThickness: CGFloat = 20.0
func addSquare(color sqcolor: SKColor) -> SKShapeNode {
let ret = SKShapeNode(rectOf: sqSize)
ret.fillColor = sqcolor
ret.physicsBody = SKPhysicsBody(rectangleOf: sqSize)
ret.physicsBody?.fieldBitMask = field1Mask
ret.position = CGPoint(x: 0.1, y: 100.0)
addChild(ret)
return ret
}
func topRightSized(size: CGSize) -> CGPoint {
CGPoint(x: Int(self.frame.width - size.width), y: Int(self.frame.height - size.height))
}
override func didMove(to view: SKView) {
print("green particles are toggled as field aware each click")
print("click or drag to move field")
self.anchorPoint = .zero // match Touchgram conventions
let centre = CGPoint(x: Int(self.frame.width)/2, y: Int(self.frame.height)/2)
let topCentre = CGPoint(x: centre.x, y: self.frame.height)
let bottomCentre = CGPoint(x: centre.x, y: wallGravityThickness/2)
let leftCentre = CGPoint(x: wallGravityThickness/2, y: self.frame.height/2)
let rightCentre = CGPoint(x: self.frame.width - wallGravityThickness, y: self.frame.height/2)
let redSq = addSquare(color: .red)
redSq.physicsBody?.mass = 100
let blueSq = addSquare(color: .blue)
blueSq.physicsBody?.charge = 100.0
redSq.physicsBody?.mass = 1
self.physicsWorld.gravity.dy = 0 // so our squares don't just fall, react only to the fields
view.showsFPS = true
view.showsFields = true
view.showsNodeCount = true
// 1. Create a massive, un-missable field
field = SKFieldNode.radialGravityField()
field.categoryBitMask = field1Mask
field.falloff = 2.0 // 0 = Uniform gravity everywhere
field.strength = 1.0
field.position = centre // Put this in the middle of your screen
field.isExclusive = false // uncomment this line and particles not affected
self.addChild(field)
let bottomWall = SKFieldNode.linearGravityField(withVector: [0,40,0])
bottomWall.categoryBitMask = bottomWallMask
bottomWall.falloff = 0 // 0 = Uniform gravity everywhere
bottomWall.position = bottomCentre // Put this in the middle of your screen
bottomWall.region = SKRegion(size: CGSize(width: frame.width, height: wallGravityThickness))
self.addChild(bottomWall)
let leftWall = SKFieldNode.linearGravityField(withVector: [40,0,0])
leftWall.categoryBitMask = bottomWallMask
leftWall.falloff = 0 // 0 = Uniform gravity everywhere
leftWall.position = leftCentre // Put this in the middle of your screen
leftWall.region = SKRegion(size: CGSize(width: wallGravityThickness, height: frame.height))
self.addChild(leftWall)
let rightWall = SKFieldNode.linearGravityField(withVector: [-40,0,0])
rightWall.categoryBitMask = bottomWallMask
rightWall.falloff = 0 // 0 = Uniform gravity everywhere
rightWall.position = rightCentre // Put this in the middle of your screen
rightWall.region = SKRegion(size: CGSize(width: wallGravityThickness, height: frame.height))
self.addChild(rightWall)
let topWall = SKFieldNode.linearGravityField(withVector: [0,-40,0])
topWall.categoryBitMask = field1Mask
topWall.falloff = 0
topWall.position = topCentre
topWall.region = SKRegion(size: CGSize(width: frame.width, height: wallGravityThickness))
self.addChild(topWall)
// simple emitters generated from Purrticles
// radiating in circle but will see gravity pulls it in
em1 = SKEmitterNode()
em1.fieldBitMask = field1Mask | bottomWallMask // Matches the field category
em1.particleBirthRate = 20
em1.emissionAngle = 1.5708 // rad (90º)
em1.emissionAngleRange = 6.2832 // rad (360º)
em1.particleLifetime = 20.0
em1.particleSpeed = 50.0
em1.particleColor = .yellow
em1.particleSize = smallParticles
em1.position = CGPoint(x: 40, y: 120) // big offset so lots of particles moving
self.addChild(em1)
em2 = SKEmitterNode() // initially not reacting to field, each touch toggles
em2.fieldBitMask = em2Mask | bottomWallMask
em2.particleBirthRate = 200
em2.emissionAngle = 1.5708 // rad (90º)
em2.emissionAngleRange = 6.2832 // rad (360º)
em2.particleLifetime = 20.0
em2.particleSpeed = 0.0
em2.particleColor = .green
em2.particleSize = smallParticles
em2.position = topRightSized(size: smallParticles)
em2.particlePositionRange = CGVector(dx: 80, dy: 40)
self.addChild(em2)
}
@objc static override var supportsSecureCoding: Bool {
get {
return true
}
}
func touchDown(atPoint pos : CGPoint) {
field.position = pos
em2Mask = 3 - em2Mask
em2.fieldBitMask = em2Mask | bottomWallMask
}
func touchMoved(toPoint pos : CGPoint) {
field.position = pos
}
func touchUp(atPoint pos : CGPoint) {
field.position = pos
}
override func mouseDown(with event: NSEvent) {
touchDown(atPoint: event.location(in: self))
}
override func mouseDragged(with event: NSEvent) {
touchMoved(toPoint: event.location(in: self))
}
override func mouseUp(with event: NSEvent) {
touchUp(atPoint: event.location(in: self))
}
}
// Load the SKScene from 'GameScene.sks'
let sceneView = SKView(frame: CGRect(x:0 , y:0, width: 640, height: 480))
if let scene = GameScene(fileNamed: "GameScene") {
// Set the scale mode to scale to fit the window
scene.scaleMode = .aspectFill
// Present the scene
sceneView.presentScene(scene)
}
PlaygroundSupport.PlaygroundPage.current.liveView = sceneView
