---
title: "Extend Reality Composer Pro 3 functionality with Xcode"
description: "Use Xcode-built Reality Composer Pro 3 plugins to expose custom RealityKit components, systems, animation actions, and Script Graph nodes to artists."
shoutout: "Unofficial, made with love by Superwall - the best way to monetize your apps."
category: "Spatial Computing"
---

# Extend Reality Composer Pro 3 functionality with Xcode


[Watch on Apple Developer](https://developer.apple.com/videos/play/wwdc2026/281/)

Use Xcode-built Reality Composer Pro 3 plugins to expose custom RealityKit components, systems, animation actions, and Script Graph nodes to artists.

## TL;DR

- Reality Composer Pro 3 can load project-specific plugin frameworks built in Xcode, letting editor content and app code share custom RealityKit types in one repository.
- Custom `Component` types must be `Codable` to appear in the editor and serialize to Reality Files; register components and systems from a `RealityComposerProPlugin`.
- Plugins can run RealityKit systems live in the editor, including driving child entities and `ShaderGraphMaterial` parameters from inspector-editable component properties.
- Custom `EntityAction` types can appear in the sequencer timeline, and `@Scriptable` can expose component schemas as custom Script Graph nodes for no-code workflows.

## Plugin architecture and team workflow

Reality Composer Pro 3 supports Xcode-built plugins so engineers can expose project-specific data and behavior directly inside the editor. Artists and designers can edit custom components, preview runtime behavior, and iterate without repeatedly building and deploying the app.

A typical project keeps the Reality Composer Pro project and Xcode project in the same git repository. The Xcode project builds both the final app and a plugin framework, while Reality Composer Pro authors scenes and exports Reality Files consumed by the app.

- Use the editor's simulation bar / Run With Xcode workflow to link the Reality Composer Pro project with the Xcode project.
- The Xcode project can have separate schemes for the app and the plugin framework, sharing custom RealityKit code between both.
- Imported assets are converted into Reality Composer Pro's internal JSON-backed data format; the editor also provides a custom merge tool intended to reduce content merge conflicts.
- When opening a project with plugins, Reality Composer Pro asks the user to trust the plugin before loading it.
- After rebuilding a plugin, restart Reality Composer Pro to load the updated dynamic library.

## Register custom components and systems

The cauldron example starts with a custom `Cauldron` component that stores a water level. Components exposed to Reality Composer Pro 3 must conform to `Codable` so they can be represented in the editor and serialized to Reality Files.

A custom RealityKit `System` queries entities with the component and runs inside the editor through the plugin. In the example, it finds a child water mesh and changes its position based on the component's inspector-editable `waterLevel` property.

- Implement custom data as a RealityKit `Component`.
- Implement editor/runtime behavior as a RealityKit `System`.
- Register both from a type conforming to `RealityComposerProPlugin`.
- Export `createRealityComposerProPlugin` with `@_cdecl` so the plugin loader can create the plugin instance.
- Debug plugin code by setting breakpoints in Xcode and attaching to the Reality Composer Pro application.

### Minimal custom component and system

Defines editor-serializable component state and a system that applies it live to the scene.

```swift
import RealityKit

public struct Cauldron: Component, Codable {
    public var waterLevel: Float
}

public struct CauldronSystem: System {
    let query = EntityComponentQuery(Cauldron.self)

    public init(scene: Scene) {}

    public func update(context: SceneUpdateContext) {
        for (entity, cauldron) in context.entities(matching: query) {
            guard let water = entity.findEntity(named: "Cauldron_Water_mesh") else { continue }
            water.setPosition(SIMD3<Float>(0, 1, 0) * cauldron.waterLevel,
                              relativeTo: entity)
        }
    }
}
```

### Reality Composer Pro plugin registration

Registers custom RealityKit types with the editor and exposes the plugin entry point.

```swift
import RealityComposerPro

final class RCPCustomComponentsPlugin: RealityComposerProPlugin {
    public func setup(context: any RealityComposerProContext) {
        context.registerComponent(Cauldron.self)
        context.registerSystem(CauldronSystem.self)
    }
}

@_cdecl("createRealityComposerProPlugin")
public func createRealityComposerProPlugin() -> UnsafeMutableRawPointer {
    return RCPCustomComponentsPlugin().passRetained()
}
```

## Drive Shader Graph materials from component data

The session extends the component with vortex-related properties, then updates the system so those properties drive a `ShaderGraphMaterial`. This lets a tech artist build the visual shader in Reality Composer Pro while engineers expose higher-level controls in Swift.

The system retrieves the water mesh's `ModelComponent`, casts the first material to `ShaderGraphMaterial`, computes derived surface parameters, sets named shader parameters, and writes the modified material back to the model.

- Use component properties such as `rotationSpeed`, `minWaterLevel`, `maxWaterLevel`, and `vortexCoeff` as editor-facing controls.
- Use `ShaderGraphMaterial.setParameter(name:value:)` to pass computed values into the shader graph.
- After changing the component's stored properties, Reality Composer Pro shows a change-acceptance dialog when the rebuilt plugin is loaded.

### Update Shader Graph parameters from a RealityKit system

Shows the core pattern for propagating component state into a Shader Graph material each update.

```swift
guard var model = water.components[ModelComponent.self] else { continue }
guard var mat = model.materials.first as? ShaderGraphMaterial else { continue }

let surface = computeSurface(cauldron: cauldron)
try? mat.setParameter(name: "Level Radius", value: .float(surface.levelRadius))
try? mat.setParameter(name: "Lowest Point", value: .float(cauldron.waterLevel - surface.lowestPoint))
try? mat.setParameter(name: "Height Change", value: .float(surface.heightChange))
try? mat.setParameter(name: "Level Coeff", value: .float(surface.levelCoeff))
try? mat.setParameter(name: "Is Level", value: .bool(surface.isLevel))

model.materials[0] = mat
water.components.set(model)
```

## Add custom animation actions to the sequencer

Reality Composer Pro 3's animation sequencer can use custom animation actions defined in a plugin. The cauldron example implements `SetWaterLevelAction`, which animates the component's `waterLevel` between start and end values on a sequencer timeline.

The action conforms to `EntityAction` and `Codable`. Execution is implemented by subscribing to `EntityAction` `.updated` events, computing normalized playback time, interpolating the water level, and writing the updated component back to the target entity.

- Return an `animatedValueType`; the example uses `Transform.self` to access the target entity in the animation executor.
- Register the action with `context.registerAction`.
- Call the action's subscription setup from plugin loading code so animation updates actually execute the action.
- In the editor, the custom action appears in the sequencer and can be dragged onto an animation track.

### Custom EntityAction for water-level animation

Defines the serializable action parameters that appear in the sequencer inspector.

```swift
import RealityKit

public struct SetWaterLevelAction: EntityAction, Codable {
    public let startWaterLevel: Float
    public let endWaterLevel: Float

    public var animatedValueType: (any AnimatableData.Type)? {
        Transform.self
    }
}
```

### Subscribe to animation updates and register the action

Executes the custom action during playback and makes it available to Reality Composer Pro.

```swift
extension SetWaterLevelAction {
    static func subscribe() {
        Task { @MainActor in
            SetWaterLevelAction.subscribe(to: .updated) { event in
                let normalizedTime = (event.playbackController.time - event.startTime) / event.duration
                let action = event.action
                let currentLevel = action.startWaterLevel +
                    Float(normalizedTime) * (action.endWaterLevel - action.startWaterLevel)

                guard let entity = event.targetEntity else { return }
                guard var cauldron = entity.components[Cauldron.self] else { return }
                cauldron.waterLevel = currentLevel
                entity.components.set(cauldron)
            }
        }
    }
}

public func setup(context: any RealityComposerProContext) {
    context.registerComponent(Cauldron.self)
    context.registerSystem(CauldronSystem.self)
    context.registerAction(SetWaterLevelAction.self)
    SetWaterLevelAction.subscribe()
}
```

## Expose custom types to Script Graph

Plugins can also add custom Script Graph nodes so designers can use project-specific Swift types in no-code graphs. The quickest path shown is annotating a custom component with `@Scriptable`, which generates a schema for scripting.

Register scripting modules on the main thread using `RealityKitScripting`. Once registered, the editor can show nodes for the custom component, such as setting the cauldron water level in response to keyboard input in a Script Graph.

- Import `RealityKitScripting` and `RealityKitScriptingMacros`.
- Add `@Scriptable` to the custom component type.
- Create an `RKS.Configuration` with one or more `Module` definitions.
- Add the generated schema, such as `Cauldron.SchemaProvider.schema`, to the module.
- Call `RKS.addConfiguration` from the plugin setup path on the main actor.

### Mark a component scriptable

Generates a schema that can be registered with the Script Graph system.

```swift
import RealityKit
import RealityKitScripting
import RealityKitScriptingMacros

@Scriptable
public struct Cauldron: Component, Codable {
    public var waterLevel: Float
    public var rotationSpeed: Float
    public var minWaterLevel: Float
    public var maxWaterLevel: Float
    public var vortexCoeff: Float
}
```

### Register a scripting module

Makes the generated custom component schema available as Script Graph nodes in the editor.

```swift
Task { @MainActor in
    let config = RKS.Configuration(id: "ChaparralVillage")
        .onInitialize { _ in
            [
                Module("ChaparralVillage") {
                    Cauldron.SchemaProvider.schema
                }
            ]
        }

    try! RKS.addConfiguration(config)
}
```

## Related Sessions

- [Design no-code games with Reality Composer Pro 3](https://wwdc.ai/2026/252)
- [Explore advances in RealityKit](https://wwdc.ai/2026/279)
- [Iterate your spatial scenes faster with Reality Composer Pro 3](https://wwdc.ai/2026/280)
- [Supercharge your spatial workflows with Reality Composer Pro 3](https://wwdc.ai/2026/393)

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