ArshTechPro

Posted on Jul 11

WWDC 2025 - SceneKit Deprecation and RealityKit Migration

#ios #mobile #programming #softwaredevelopment

Understanding the Frameworks

SceneKit: The Legacy 3D Framework

SceneKit has been Apple's 3D graphics framework since OS X Mountain Lion (13 years ago).
Key characteristics:

Node-based architecture: Every object is a node with predefined properties
Flexible asset support: Accepts various model formats, serializes to SCN files
Platform limitations: Designed for older architectural patterns
Proprietary formats: Uses non-standard asset pipelines

RealityKit: The Modern 3D Engine

RealityKit represents Apple's next-generation 3D framework built for modern development:

Entity Component System (ECS): Modular architecture where entities have attachable components
SwiftUI-first design: Native integration with modern UI paradigms
Cross-platform support: visionOS, iOS, macOS, iPadOS, and tvOS
Industry standards: Built around Universal Scene Description (USD) format
Advanced rendering: Stereoscopic rendering, post-processing effects, and modern graphics pipeline

SceneKit Deprecation: What Developers Need to Know

Deprecation Status

Soft deprecation: Existing SceneKit applications continue to work
Maintenance mode: Only critical bug fixes, no new features or optimizations
Migration window: No hard deprecation timeline announced
Recommendation: Avoid SceneKit for new projects or significant updates

Migration Strategy

Existing projects: Continue operating without immediate changes required
New development: Use RealityKit for all new 3D applications
Updates: Consider migration when planning major feature additions

Core Architectural Differences

SceneKit: Node-Based Architecture

// SceneKit approach
let node = SCNNode()
node.geometry = maxModel
node.addAudioPlayer(audioPlayer)
node.addAnimationPlayer(animationPlayer, forKey: "spin")

RealityKit: Entity Component System

// RealityKit approach
let entity = Entity()
entity.components[ModelComponent.self] = ModelComponent(...)
entity.components[AudioLibraryComponent.self] = AudioLibraryComponent(...)
entity.components[AnimationLibraryComponent.self] = AnimationLibraryComponent(...)

Technical Migration Areas

1. Coordinate Systems

Identical systems: Both use right-handed coordinate system
X-axis: Points right
Y-axis: Points up
Z-axis: Points toward camera
Migration impact: Zero changes required

2. Asset Conversion

From SCN to USD

Xcode Method:

Select SCN asset in Xcode
File → Export → Universal Scene Description Package
Automated conversion with variable results

CLI Method:

# Convert geometry
xcrun scntool --convert max.scn --format usdz

# Convert with animations
xcrun scntool --convert max.scn --format usdz --append-animation max_spin.scn

Asset Pipeline Advantages

Industry standard: USD format used across major studios
Collaboration: Better data exchange between tools
Future-proof: Pixar-developed standard with wide adoption

3. Scene Composition Tools

SceneKit Editor → Reality Composer Pro

Integrated workflow: Ships with Xcode
Visual composition: Drag-and-drop scene building
Component editing: Direct manipulation of entity components
Material authoring: Advanced shader and material creation
Swift package integration: Seamless Xcode integration

Implementation Pattern

// Import generated package
import RealityKit
import PyroPanda

// Load scene
let scene = try await Entity.load(named: "Scene", in: Bundle.main)

// Add to RealityView
RealityView { content in
    content.add(scene)
}

4. Animation Systems

SceneKit Animation Pattern

// SceneKit - Complex traversal required
let maxNode = scene.rootNode.childNode(withName: "Max_rootNode", recursively: true)
let animationScene = SCNScene(named: "max_spin.scn")
let animationPlayer = animationScene.rootNode.childNodes.first?.animationPlayer(forKey: "spin")
maxNode.addAnimationPlayer(animationPlayer, forKey: "spin")
maxNode.animationPlayer(forKey: "spin")?.play()

RealityKit Animation Pattern

// RealityKit - Direct component access
guard let max = scene.findEntity(named: "Max") else { return }
guard let library = max.components[AnimationLibraryComponent.self],
      let spinAnimation = library.animations["spin"]
else { return }

max.playAnimation(spinAnimation)

5. Lighting Implementation

SceneKit Lighting

// SceneKit
let light = SCNLight()
light.type = .directional
light.castsShadow = true

let lightNode = SCNNode()
lightNode.light = light
scene.rootNode.addChildNode(lightNode)

RealityKit Lighting

// RealityKit - Component-based approach
let lightEntity = Entity()
lightEntity.components[DirectionalLightComponent.self] = DirectionalLightComponent()
lightEntity.components[DirectionalLightComponent.Shadow.self] = DirectionalLightComponent.Shadow()

// Alternative: Direct initialization with components
let lightEntity = Entity(components:
    DirectionalLightComponent(),
    DirectionalLightComponent.Shadow()
)

6. Audio Integration

SceneKit Audio Workflow

// SceneKit - Runtime configuration
let audioSource = SCNAudioSource(fileNamed: "ambient.mp3")
audioSource.loops = true
audioSource.isPositional = false
let audioPlayer = SCNAudioPlayer(source: audioSource)
terrainNode.addAudioPlayer(audioPlayer)

RealityKit Audio Workflow

Reality Composer Pro Configuration:

Attach AudioLibraryComponent to entity
Configure ambient audio component
Set streaming and loop properties
Zero runtime configuration required

Code Implementation:

// Method 1: Direct component access
guard let library = terrain.components[AudioLibraryComponent.self] else { return }
let audioResource = library.audioResources["ambient"]
terrain.playAudio(audioResource)

// Method 2: Entity actions
let playAction = PlayAudioAction(audioResourceName: "ambient")
let animation = AnimationDefinition(playAction)
terrain.playAnimation(animation)

7. Visual Effects and Post-Processing

Particle System Migration

No direct conversion: SCN particle files require manual recreation
Reality Composer Pro: Visual particle editor with preset options
Component-based: ParticleEmitterComponent with extensive customization
Performance optimization: Better memory management and rendering

Post-Processing Pipeline

// Custom bloom effect implementation
final class BloomPostProcess: PostProcessEffect {
    let bloomThreshold: Float = 0.5
    let bloomBlurRadius: Float = 15.0

    func postProcess(context: borrowing PostProcessEffectContext<any MTLCommandBuffer>) {
        // Create metal texture of the same format as 'context.sourceColorTexture'
        var bloomTexture = ...

        // Write brightest parts using 'MPSImageThresholdToZero'
        // Blur 'bloomTexture' in-place using 'MPSImageGaussianBlur'
        // Combine textures using 'MPSImageAdd'
    }
}

// Apply to RealityView
content.renderingEffects.customPostProcessing = .effect(BloomPostProcess())