Reality Composer Pro 3 Plugin Extensions

import RealityKit
import RealityComposerPro

// MARK: - Custom Component

public struct CauldronComponent: Component, Codable {
    /// Normalized water level: 0 = empty, 1 = full
    public var waterLevel: Float = 0.5
    /// Speed of the vortex rotation in radians/sec
    public var rotationSpeed: Float = 0.0
    /// How deep the vortex funnel becomes (0 = flat)
    public var vortexCoefficient: Float = 0.0

    public init() {}
}

// MARK: - Custom System

public class CauldronSystem: System {
    private static let query = EntityQuery(
        where: .has(CauldronComponent.self)
    )

    public required init(scene: Scene) {}

    public func update(context: SceneUpdateContext) {
        for entity in context.entities(matching: Self.query,
                                       updatingSystemWhen: .rendering) {
            guard let cauldron = entity.components[CauldronComponent.self],
                  let waterMesh = entity.findEntity(named: "WaterSurface")
            else { continue }

            // Lift the water plane based on the normalized level
            let baseY: Float = -0.15
            let range: Float = 0.30
            waterMesh.position.y = baseY + cauldron.waterLevel * range

            // Push shader graph parameters when a ModelComponent is present
            if var model = waterMesh.components[ModelComponent.self] {
                if var param = model.materials.first as? ShaderGraphMaterial {
                    try? param.setParameter(
                        name: "RotationSpeed",
                        value: .float(cauldron.rotationSpeed)
                    )
                    try? param.setParameter(
                        name: "VortexCoefficient",
                        value: .float(cauldron.vortexCoefficient)
                    )
                    model.materials = [param]
                    waterMesh.components.set(model)
                }
            }
        }
    }
}

// MARK: - Plugin Entry Point

public class CauldronPlugin: RealityComposerProPlugin {
    public required init() {}

    public func setup(context: RealityComposerProPluginContext) {
        context.registerComponent(CauldronComponent.self)
        context.registerSystem(CauldronSystem.self)
    }
}

@_cdecl("createRealityComposerProPlugin")
public func createRealityComposerProPlugin() -> UnsafeMutableRawPointer {
    return Unmanaged.passRetained(CauldronPlugin()).toOpaque()
}