Question

我不知道如何重复下面的move函数，以便在简单的meshResource上创建恒定的旋转。有什么建议吗？

var transform = sphereEntity.transform
transform.rotation =  simd_quatf(angle: .pi, axis: [0,1,0])
let anim = sphereEntity.move(to: transform, relativeTo: sphereEntity.parent, duration: 5.0)

Answer 1

任何move()实例方法都可以在将实体添加到场景的瞬间之后使用。

let boxEntity = ModelEntity(mesh: .generateBox(size: 1.0), 
                       materials: [SimpleMaterial()])

var transform = boxEntity.transform

transform.rotation =  simd_quatf(angle: .pi,
                                  axis: [0, 1, 0])

let boxAnchor = AnchorEntity()
boxAnchor.children.append(boxEntity)
arView.scene.anchors.append(boxAnchor)

boxEntity.move(to: transform, relativeTo: nil, duration: 5.0)

目前（ 2020年3月4日），所有RealityKit的move()实例方法无法循环。

Answer 2

通过订阅 AnimationEvents.PlaybackCompleted 事件可以循环播放动画。

您必须将动画逻辑移动到单独调用一次的函数中。在此函数中，您订阅 PlaybackCompleted 事件。触发此事件时，您将调用相同的动画函数。

您可以使用 AnimationEvents 方法订阅 Scene.subscribe()：

func subscribe<E>(to event: E.Type, 
                  on sourceObject: EventSource? = nil, 
                  _ handler: @escaping (E) -> Void) -> Cancellable where E : Event

请注意，您必须导入Combine 框架才能使用它：

import Combine

动画函数如下所示：

// This needs to be an instance variable, otherwise it'll
// get deallocated immediately and the animation won't start.
var animUpdateSubscription: Cancellable?

func animate(entity: HasTransform,
             angle: Float,
             axis: SIMD3<Float>,
             duration: TimeInterval,
             loop: Bool)
{
    var transform = entity.transform
    // We'll add the rotation to the current rotation
    transform.rotation *= simd_quatf(angle: angle, axis: axis)
    entity.move(to: transform, relativeTo: entity.parent, duration: duration)
    
    // Checks if we should loop and if we have already subscribed
    // to the AnimationEvent. We only need to do this once. 
    guard loop,
          animUpdateSubscription == nil
    else { return }
    
    animUpdateSubscription = scene.subscribe(to: AnimationEvents.PlaybackCompleted.self, 
                                             on: entity, 
    { _ in
        self.animate(entity: entity, 
                     angle: angle, 
                     axis: axis, 
                     duration: duration, 
                     loop: loop)
    })
}

现在你可以调用一次这个函数来触发一个循环动画：

animate(entity: entity, 
        angle: angle, 
        axis: axis, 
        duration: duration, 
        loop: loop)

RealityKit –动画循环播放

2 个答案: