/scenekit

name: scenekit
description: "Maintain and extend existing SceneKit 3D scenes and visualizations. Use when working with SCNView, SCNScene, SCNNode scene graphs, SceneKit geometry/materials/lights/cameras, SCNAction animation, SCNPhysicsBody physics, SCNParticleSystem effects, .scn/.dae/.abc SceneKit assets, shader modifiers, or SwiftUI SceneView. SceneKit is soft-deprecated and in maintenance mode; route new apps, significant updates, USD/USDZ pipelines, and migration planning toward RealityKit."

SceneKit

Maintain existing SceneKit scenes only. Apple deprecated SceneKit at WWDC 2025 and limits it to maintenance; route new projects, major modernization, and USD/USDZ pipelines to RealityKit. Existing apps continue to work.

Contents

• [Scene Setup](#scene-setup)
• [Nodes and Geometry](#nodes-and-geometry)
• [Materials](#materials)
• [Lighting](#lighting)
• [Cameras](#cameras)
• [Animation](#animation)
• [Physics](#physics)
• [Particle Systems](#particle-systems)
• [Loading Models](#loading-models)
• [SwiftUI Integration](#swiftui-integration)
• [Common Mistakes](#common-mistakes)
• [Review Checklist](#review-checklist)
• [References](#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 in .scnassets
    else { fatalError("Missing scene asset") }
let url = Bundle.main.url(forResource: "ship", withExtension: "dae")!
let scene = try SCNScene(url: url, options: [.checkConsistency: true])

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.rootN