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

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 allowsCameraControl adds built in orbit, pan, and zoom gestures. Typically disabled in production where custom camera control is needed. Creating an SCNScene 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. Transforms Built in Primitives SCNBox , SCNSphere , SCNCylinder , SCNCone , SCNTorus , SCNCapsule , SCNTube , SCNPlane , SCNFloor , SCNText , SCNShape (extruded Bezier path). Finding Nodes Materials SCNMaterial defines surface appearance. Use firstMaterial for single material geometries or the materials array for multi material. Color and Texture Physically Based Rendering (PBR) 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 Lighting Attach an SCNLight to a node. The light's direction follows the node's negative Z axis. Light Types Attach to a node: Shadows Category Bit Masks 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. Configuration 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. SCNTransaction (Implicit Animation) Explicit Animations (Core Animation) Physics Physics Bodies When shape is nil , SceneKit derives it from geometry. For performance, use simplified shapes: Applying Forces Collision Detection Gravity Particle Systems SCNParticleSystem creates effects like fire, smoke, rain, and sparks. Load from Xcode particle editor with SCNParticleSystem(named: "fire.scnp", inDirectory: nil) . Particles can collide with geometry via colliderNodes . Loading Models SceneKit's documented scene source formats are .scn , .dae , and .abc . For bundled assets, place scene files in a .scnassets folder and texture images in asset catalogs so Xcode can optimize them for target devices. USD/USDZ is the RealityKit migration path, not the default SceneKit loading path. For new projects, significant updates, or SCN to USD asset conversion, handoff to the RealityKit skill. Use this as an authoring/import gate: stop on a consistency or required node failure, fix the source asset or import options, then repeat the same check. For generated .scn files, load [Scene Serialization](references/scenekit patterns.md scene serialization) and require both export success and a checked reload before commit. Use SCNReferenceNode with .onDemand loading policy for large models. For import time unit conversion, use SCNSceneSource.LoadingOption : Do not use SCNScene.Attribute.unit or UnitMetersPerUnit . SCNScene.Attribute is metadata only: .startTime , .endTime , .frameRate , and .upAxis . SwiftUI Integration SceneView embeds SceneKit in SwiftUI: Options: .allowsCameraControl , .autoenablesDefaultLighting , .jitteringEnabled , .temporalAntialiasingEnabled . For render loop control, wrap SCNView in UIViewRepresentable with an SCNSceneRendererDelegate coordinator. See [references/scenekit patterns.md](references/scenekit patterns.md). Common Mistakes Not adding a camera or lights Using exact geometry for physics shapes Modifying transforms on dynamic bodies 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 [ ] SceneKit assets use documented .scn , .dae , or .abc scene source formats [ ] Imported and exported assets pass consistency and required node checks before commit [ ] Bundled SceneKit textures/images use asset catalogs or Xcode optimized resources [ ] Scene metadata/import options use documented API; no invented SCNScene.Attribute.unit [ ] New USD/USDZ pipelines or significant updates are routed to RealityKit [ ] Game Center authentication, leaderboards, achievements, or multiplayer are handed off to GameKit [ ] 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](references/scenekit patterns.md) for custom geometry, shader modifiers, constraints, morph targets, hit testing, scene serialization, render loop delegates, performance, SpriteKit overlay, LOD, and Metal shaders. [SceneKit documentation](https://sosumi.ai/documentation/scenekit), [SCNSceneSource](https://sosumi.ai/documentation/scenekit/scnscenesource), [SCNView](https://sosumi.ai/documentation/scenekit/scnview), [SceneView](https://sosumi.ai/documentation/scenekit/sceneview) [SCNPhysicsShape](https://sosumi.ai/documentation/scenekit/scnphysicsshape), [SCNShadable](https://sosumi.ai/documentation/scenekit/scnshadable) [WWDC 2025 session 288: Bring your SceneKit project to RealityKit](https://sosumi.ai/videos/play/wwdc2025/288/)