Reality Composer Pro 3 — Animation Graph & Behavior Tree

import SwiftUI
import RealityKit
import RealityKitContent

// MARK: - SwiftUI entry point

@main
struct AlchemistApp: App {
    var body: some Scene {
        WindowGroup {
            AlchemistView()
        }
    }
}

// MARK: - View

struct AlchemistView: View {
    @State private var rootEntity: Entity?
    @State private var alchemist: Entity?

    var body: some View {
        RealityView { content in
            // Load the scene exported from Reality Composer Pro 3
            // The scene contains the Animation Graph and Behavior Tree components
            if let scene = try? await Entity(named: "AlchemyArea", in: realityKitContentBundle) {
                content.add(scene)
                rootEntity = scene

                // Grab the alchemist entity by name (as set in RCP3 scene graph)
                alchemist = scene.findEntity(named: "Alchemist")
            }
        } update: { _ in
            // RealityView update closure — nothing needed here for this demo
        }
        .gesture(
            TapGesture().targetedToAnyEntity().onEnded { value in
                guard let alchemist,
                      value.entity == alchemist else { return }
                triggerBrewingRoutine(on: alchemist)
            }
        )
        .onAppear {
            // After a short delay, start the idle-to-table routine
            Task {
                try? await Task.sleep(for: .seconds(1))
                if let alchemist {
                    startTableRoutine(on: alchemist)
                }
            }
        }
    }

    // MARK: - Animation Graph parameter helpers

    /// Sets the Animation Graph `isWalking` boolean parameter on the entity.
    private func setWalking(_ walking: Bool, on entity: Entity) {
        // AnimationGraphComponent exposes a parameters dictionary
        // keyed by the input names defined in Reality Composer Pro 3.
        if var animGraph = entity.components[AnimationGraphComponent.self] {
            animGraph.parameters["isWalking"] = .bool(walking)
            entity.components[AnimationGraphComponent.self] = animGraph
        }
    }

    // MARK: - Behavior Tree helpers

    /// Activates the table sub-sequence by ensuring readyToBrew is false.
    private func startTableRoutine(on entity: Entity) {
        if var behaviorTree = entity.components[BehaviorTreeComponent.self] {
            behaviorTree.parameters["readyToBrew"] = .bool(false)
            entity.components[BehaviorTreeComponent.self] = behaviorTree
        }
        setWalking(true, on: entity)
    }

    /// Called when user taps the alchemist — triggers the cauldron sub-sequence.
    private func triggerBrewingRoutine(on entity: Entity) {
        if var behaviorTree = entity.components[BehaviorTreeComponent.self] {
            behaviorTree.parameters["readyToBrew"] = .bool(true)
            entity.components[BehaviorTreeComponent.self] = behaviorTree
        }
        setWalking(true, on: entity)
    }
}