SceneKit

Apple's high-level 3D rendering framework for building scenes and visualizations on iOS using Swift 6.3. Provides a node-based scene graph, built-in geometry primitives, physically based materials, lighting, animation, and physics.

Deprecation notice (WWDC 2025): SceneKit is officially deprecated across all Apple platforms and is now in maintenance mode (critical bug fixes only). Existing apps continue to work. For new projects or major updates, Apple recommends RealityKit. See WWDC 2025 session 288 for migration guidance.

Contents

• Scene Setup
• Nodes and Geometry
• Materials
• Lighting
• Cameras
• Animation
• Physics
• Particle Systems
• Loading Models
• SwiftUI Integration
• Common Mistakes
• Review Checklist
• References

Scene Setup

SCNView in UIKit

import SceneKit

let sceneView = SCNView(frame: view.bounds)
sceneView.scene = SCNScene()
sceneView.allowsCameraControl = true
sceneView.autoenablesDefaultLighting = true
sceneView.backgroundColor = .black
view.addSubview(sceneView)

allowsCameraControl

adds built-in orbit, pan, and zoom gestures. Typically disabled in production where custom camera control is needed.

Creating an SCNScene

let scene = SCNScene()                                          // Empty
guard let scene = SCNScene(named: "art.scnassets/ship.scn")     // .scn asset catalog
    else { fatalError("Missing scene asset") }
let scene = try SCNScene(url: Bundle.main.url(                  // .usdz from bundle
    forResource: "spaceship", withExtension: "usdz")!)

Nodes and Geometry

Every scene has a

rootNode

. All content exists as descendant nodes. Nodes define position, orientation, and scale in their parent's coordinate system. SceneKit uses a right-handed coordinate system: +X right, +Y up, +Z toward the camera.

let parentNode = SCNNode()
scene.rootNode.addChildNode(parentNode)

let childNode = SCNNode()
childNode.position = SCNVector3(0, 1, 0)  // 1 unit above parent
parentNode.addChildNode(childNode)

Transforms

node.position = SCNVector3(x: 0, y: 2, z: -5)
node.eulerAngles = SCNVector3(x: 0, y: .pi / 4, z: 0)  // 45-degree Y rotation
node.scale = SCNVector3(2, 2, 2)
node.simdPosition = SIMD3<Float>(0, 2, -5)  // Prefer simd for performance

Built-in Primitives

SCNBox

,

SCNSphere

,

SCNCylinder

,

SCNCone

,

SCNTorus

,

SCNCapsule

,

SCNTube

,

SCNPlane

,

SCNFloor

,

SCNText

,

SCNShape

(extruded Bezier path).

let node = SCNNode(geometry: SCNSphere(radius: 0.5))

Finding Nodes

let maxNode = scene.rootNode.childNode(withName: "Max", recursively: true)
let enemies = scene.rootNode.childNodes { node, _ in
    node.name?.hasPrefix("enemy") == true
}

Materials

SCNMaterial

defines surface appearance. Use

firstMaterial

for single-material geometries or the

materials

array for multi-material.

Color and Texture

let material = SCNMaterial()
material.diffuse.contents = UIColor.systemBlue     // Solid color
material.diffuse.contents = UIImage(named: "brick") // Texture
material.normal.contents = UIImage(named: "brick_normal")
sphere.firstMaterial = material

Physically Based Rendering (PBR)

let pbr = SCNMaterial()
pbr.lightingModel = .physicallyBased
pbr.diffuse.contents = UIImage(named: "albedo")
pbr.metalness.contents = 0.8       // Scalar or texture
pbr.roughness.contents = 0.2       // Scalar or texture
pbr.normal.contents = UIImage(named: "normal")
pbr.ambientOcclusion.contents = UIImage(named: "ao")

Lighting Models

.physicallyBased

(metalness/roughness),

.blinn

(default),

.phong

,

.lambert

(diffuse-only),

.constant

(unlit),

.shadowOnly

.

Each material property is an

SCNMaterialProperty

accepting

UIColor

,

UIImage

,

CGFloat

scalar,

SKTexture

,

CALayer

, or

AVPlayer

.

Transparency

material.transparency = 0.5
material.transparencyMode = .dualLayer
material.isDoubleSided = true

Lighting

Attach an

SCNLight

to a node. The light's direction follows the node's negative Z-axis.

Light Types

// Ambient: uniform, no direction
let ambient = SCNLight()
ambient.type = .ambient
ambient.color = UIColor(white: 0.3, alpha: 1)

// Directional: parallel rays (sunlight)
let directional = SCNLight()
directional.type = .directional
directional.castsShadow = true

// Omni: point light, all directions
let omni = SCNLight()
omni.type = .omni
omni.attenuationEndDistance = 20

// Spot: cone-shaped
let spot = SCNLight()
spot.type = .spot
spot.spotInnerAngle = 20
spot.spotOuterAngle = 60

Attach to a node:

let lightNode = SCNNode()
lightNode.light = directional
lightNode.eulerAngles = SCNVector3(-Float.pi / 3, 0, 0)
lightNode.position = SCNVector3(0, 10, 10)
scene.rootNode.addChildNode(lightNode)

Shadows

light.castsShadow = true
light.shadowMapSize = CGSize(width: 2048, height: 2048)
light.shadowSampleCount = 8
light.shadowRadius = 3.0
light.shadowColor = UIColor(white: 0, alpha: 0.5)

Category Bit Masks

light.categoryBitMask = 1 << 1     // Category 2
node.categoryBitMask = 1 << 1      // Only lit by category-2 lights

SceneKit renders a maximum of 8 lights per node. Use

attenuationEndDistance

on point/spot lights so SceneKit skips them for distant nodes.

Cameras

Attach an

SCNCamera

to a node to define a viewpoint.

let cameraNode = SCNNode()
cameraNode.camera = SCNCamera()
cameraNode.position = SCNVector3(0, 5, 15)
cameraNode.look(at: SCNVector3Zero)
scene.rootNode.addChildNode(cameraNode)
sceneView.pointOfView = cameraNode

Configuration

camera.fieldOfView = 60                        // Degrees
camera.zNear = 0.1
camera.zFar = 500
camera.automaticallyAdjustsZRange = true

// Orthographic
camera.usesOrthographicProjection = true
camera.orthographicScale = 10

Depth-of-field (

wantsDepthOfField

,

focusDistance

,

fStop

) and HDR effects (

wantsHDR

,

bloomIntensity

,

bloomThreshold

,

screenSpaceAmbientOcclusionIntensity

) are configured directly on

SCNCamera

.

Animation

SceneKit provides three animation approaches.

SCNAction (Declarative, Game-Oriented)

Reusable, composable animation objects attached to nodes.

let move = SCNAction.move(by: SCNVector3(0, 2, 0), duration: 1)
let rotate = SCNAction.rotateBy(x: 0, y: .pi, z: 0, duration: 1)
node.runAction(.group([move, rotate]))

// Sequential
node.runAction(.sequence([.fadeOut(duration: 0.3), .removeFromParentNode()]))

// Infinite loop
let pulse = SCNAction.sequence([
    .scale(to: 1.2, duration: 0.5),
    .scale(to: 1.0, duration: 0.5)
])
node.runAction(.repeatForever(pulse))

SCNTransaction (Implicit Animation)

SCNTransaction.begin()
SCNTransaction.animationDuration = 1.0
node.position = SCNVector3(5, 0, 0)
node.opacity = 0.5
SCNTransaction.completionBlock = { print("Done") }
SCNTransaction.commit()

Explicit Animations (Core Animation)

let animation = CABasicAnimation(keyPath: "rotation")
animation.toValue = NSValue(scnVector4: SCNVector4(0, 1, 0, Float.pi * 2))
animation.duration = 2
animation.repeatCount = .infinity
node.addAnimation(animation, forKey: "spin")

Physics

Physics Bodies

node.physicsBody = SCNPhysicsBody(type: .dynamic, shape: nil)   // Forces + collisions
floor.physicsBody = SCNPhysicsBody(type: .static, shape: nil)    // Immovable
platform.physicsBody = SCNPhysicsBody(type: .kinematic, shape: nil) // Code-driven

When

shape

is

nil

, SceneKit derives it from geometry. For performance, use simplified shapes:

let shape = SCNPhysicsShape(
    geometry: SCNBox(width: 1, height: 2, length: 1, chamferRadius: 0),
    options: nil
)
node.physicsBody = SCNPhysicsBody(type: .dynamic, shape: shape)
node.physicsBody?.mass = 2.0
node.physicsBody?.restitution = 0.3

Applying Forces

node.physicsBody?.applyForce(SCNVector3(0, 10, 0), asImpulse: false) // Continuous
node.physicsBody?.applyForce(SCNVector3(0, 5, 0), asImpulse: true)   // Instant
node.physicsBody?.applyTorque(SCNVector4(0, 1, 0, 2), asImpulse: true)

Collision Detection

struct PhysicsCategory {
    static let player:     Int = 1 << 0
    static let enemy:      Int = 1 << 1
    static let ground:     Int = 1 << 2
}

playerNode.physicsBody?.categoryBitMask = PhysicsCategory.player
playerNode.physicsBody?.collisionBitMask = PhysicsCategory.ground | PhysicsCategory.enemy
playerNode.physicsBody?.contactTestBitMask = PhysicsCategory.enemy

scene.physicsWorld.contactDelegate = self

func physicsWorld(_ world: SCNPhysicsWorld, didBegin contact: SCNPhysicsContact) {
    handleCollision(between: contact.nodeA, and: contact.nodeB)
}

Gravity

scene.physicsWorld.gravity = SCNVector3(0, -9.8, 0)
node.physicsBody?.isAffectedByGravity = false

Particle Systems

SCNParticleSystem

creates effects like fire, smoke, rain, and sparks.

let particles = SCNParticleSystem()
particles.birthRate = 100
particles.particleLifeSpan = 2
particles.particleSize = 0.1
particles.particleColor = .orange
particles.emitterShape = SCNSphere(radius: 0.5)
particles.particleVelocity = 2
particles.isAffectedByGravity = true
particles.blendMode = .additive

let emitterNode = SCNNode()
emitterNode.addParticleSystem(particles)
scene.rootNode.addChildNode(emitterNode)

Load from Xcode particle editor with

SCNParticleSystem(named: "fire.scnp", inDirectory: nil)

. Particles can collide with geometry via

colliderNodes

.

Loading Models

SceneKit loads

.usdz

,

.scn

,

.dae

,

.obj

, and

.abc

. Prefer

.usdz

.

guard let scene = SCNScene(named: "art.scnassets/ship.scn") else { return }
let scene = try SCNScene(url: Bundle.main.url(
    forResource: "model", withExtension: "usdz")!)
guard let modelNode = scene.rootNode.childNode(withName: "mesh", recursively: true) else { return }

Use

SCNReferenceNode

with

.onDemand

loading policy for large models. Use

SCNSceneSource

to inspect or selectively load entries from a file.

SwiftUI Integration

SceneView

embeds SceneKit in SwiftUI:

import SwiftUI
import SceneKit

struct SceneKitView: View {
    let scene: SCNScene = {
        let scene = SCNScene()
        let sphere = SCNNode(geometry: SCNSphere(radius: 1))
        sphere.geometry?.firstMaterial?.lightingModel = .physicallyBased
        sphere.geometry?.firstMaterial?.diffuse.contents = UIColor.systemBlue
        sphere.geometry?.firstMaterial?.metalness.contents = 0.8
        scene.rootNode.addChildNode(sphere)
        return scene
    }()

    var body: some View {
        SceneView(scene: scene,
                  options: [.allowsCameraControl, .autoenablesDefaultLighting])
    }
}

Options:

.allowsCameraControl

,

.autoenablesDefaultLighting

,

.jitteringEnabled

,

.temporalAntialiasingEnabled

.

For render loop control, wrap

SCNView

in

UIViewRepresentable

with an

SCNSceneRendererDelegate

coordinator. See references/scenekit-patterns.md.

Common Mistakes

Not adding a camera or lights

// DON'T: Scene renders blank or black -- no camera, no lights
sceneView.scene = scene

// DO: Add camera + lights, or use convenience flags
let cameraNode = SCNNode()
cameraNode.camera = SCNCamera()
cameraNode.position = SCNVector3(0, 5, 15)
scene.rootNode.addChildNode(cameraNode)
sceneView.pointOfView = cameraNode
sceneView.autoenablesDefaultLighting = true

Using exact geometry for physics shapes

// DON'T
node.physicsBody = SCNPhysicsBody(type: .dynamic,
    shape: SCNPhysicsShape(geometry: complexMesh))

// DO: Simplified primitive
node.physicsBody = SCNPhysicsBody(type: .dynamic,
    shape: SCNPhysicsShape(
        geometry: SCNBox(width: 1, height: 2, length: 1, chamferRadius: 0),
        options: nil))

Modifying transforms on dynamic bodies

// DON'T: Resets physics simulation
dynamicNode.position = SCNVector3(5, 0, 0)

// DO: Use forces/impulses
dynamicNode.physicsBody?.applyForce(SCNVector3(10, 0, 0), asImpulse: true)

Exceeding 8 lights per node

// DON'T: 20 lights with no attenuation
for _ in 0..<20 {
    let light = SCNNode()
    light.light = SCNLight()
    light.light?.type = .omni
    scene.rootNode.addChildNode(light)
}

// DO: Set attenuationEndDistance so SceneKit skips distant lights
light.light?.attenuationEndDistance = 10

Review Checklist

• Scene has at least one camera node set as

  pointOfView

• Scene has appropriate lighting (or

  autoenablesDefaultLighting

  for prototyping)
• Physics shapes use simplified geometry, not full mesh detail

• contactTestBitMask

  set for bodies that need collision callbacks

• SCNPhysicsContactDelegate

  assigned to

  scene.physicsWorld.contactDelegate

• Dynamic body transforms changed via forces/impulses, not direct position
• Lights limited to 8 per node;

  attenuationEndDistance

  set on point/spot lights
• Materials use

  .physicallyBased

  lighting model for realistic rendering
• 3D assets use

  .usdz

  format where possible

• SCNReferenceNode

  used for large models to enable lazy loading
• Particle

  birthRate

  and

  particleLifeSpan

  balanced to control particle count

• categoryBitMask

  used to scope lights and cameras to relevant nodes
• SwiftUI scenes use

  SceneView

  or

  UIViewRepresentable

  -wrapped

  SCNView

• Deprecation acknowledged; RealityKit evaluated for new projects

References

• See references/scenekit-patterns.md for custom geometry, shader modifiers, node constraints, morph targets, hit testing, scene serialization, render loop delegates, performance optimization, SpriteKit overlay, LOD, and Metal shaders.
• SceneKit documentation
• SCNScene
• SCNNode
• SCNView
• SceneView (SwiftUI)
• SCNGeometry
• SCNMaterial
• SCNLight
• SCNCamera
• SCNAction
• SCNPhysicsBody
• SCNParticleSystem
• WWDC 2025 session 288: Bring your SceneKit project to RealityKit