3D World & Physics

import SpriteKit

class GravityScene: SKScene {
    override func didMove(to view: SKView) {
        physicsBody = SKPhysicsBody(edgeLoopFrom: frame)
        physicsWorld.gravity = CGVector(dx: 0, dy: -9.8)
    }

    override func touchesBegan(_ touches: Set<UITouch>, with: UIEvent?) {
        guard let t = touches.first else { return }
        let ball = SKShapeNode(circleOfRadius: 20)
        ball.position = t.location(in: self)
        ball.physicsBody = SKPhysicsBody(circleOfRadius: 20)
        ball.physicsBody?.restitution = 0.6   // 탄성
        addChild(ball)
    }
}

import SceneKit

let scene = SCNScene()
let sphere = SCNSphere(radius: 1.0)
sphere.firstMaterial?.diffuse.contents = UIColor.orange

let node = SCNNode(geometry: sphere)
node.position = SCNVector3(0, 0, -3)
scene.rootNode.addChildNode(node)

// Continuous rotation
let spin = SCNAction.rotateBy(x: 0, y: .pi * 2, z: 0, duration: 4)
node.runAction(SCNAction.repeatForever(spin))

let emitter = CAEmitterLayer()
emitter.emitterShape = .line
emitter.emitterPosition = CGPoint(x: view.bounds.midX, y: 0)
emitter.emitterSize = CGSize(width: view.bounds.width, height: 1)

let cell = CAEmitterCell()
cell.contents = UIImage(systemName: "snowflake")?.cgImage
cell.birthRate = 10          // per second
cell.lifetime = 6
cell.velocity = 80
cell.velocityRange = 40
cell.yAcceleration = 20
cell.spinRange = .pi

emitter.emitterCells = [cell]
view.layer.addSublayer(emitter)