Best practice for low-latency hinge-driven gameplay on iPhone Duo

Question

Created 8h

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This post is from the Activity iPhone Duo SwiftUI Q&A.

I’m building a real-time game where the iPhone Duo hinge angle will drive a continuous in-game “reality shift” effect as the device opens and closes. For an interactive game, what update frequency and latency should developers expect from the hinge-angle APIs? Is it appropriate to use continuous hinge updates to drive visual state frame-by-frame, or should apps sample/debounce the values? Also, if the main renderer is not SwiftUI, for example Metal or Unreal Engine through a small native bridge, is there a recommended pattern for observing hinge changes and synchronizing them with the game render loop? I’m especially interested in any guidance around avoiding jitter, delayed updates, or excessive work during rapid folding/unfolding.

Answered by JCarter1 in 906531022

Thank you, that clarifies the timing expectations. We’ll avoid assuming a fixed update rate and evaluate light smoothing, using the latest hinge reading as a target for our existing game-loop animation. For a UIKit-hosted Metal/Unreal rendering view, would UIHingeInteraction be the recommended way to observe hinge changes without adding a SwiftUI overlay? Also, do the updates expose a measurement timestamp, or should we record callback-receipt time when evaluating responsiveness?

Answer 1

Frameworks Engineer OP

Apple

7h

For an interactive game, what update frequency and latency should developers expect from the hinge-angle APIs?

There is no guaranteed update frequency for our hinge APIs. The frequency is determined by the system and is a result of multiple factors.

Is it appropriate to use continuous hinge updates to drive visual state frame-by-frame, or should apps sample/debounce the values?

This really depends on what you are using these APIs to drive in your app. For many situations using the updates directly will be fine. But because there's no guaranteed frequency or angle increment, others may require some smoothing, like through a spring animation.

Answer 2

JCarter1 OP

6h

Accepted Answer

Thank you, that clarifies the timing expectations. We’ll avoid assuming a fixed update rate and evaluate light smoothing, using the latest hinge reading as a target for our existing game-loop animation. For a UIKit-hosted Metal/Unreal rendering view, would UIHingeInteraction be the recommended way to observe hinge changes without adding a SwiftUI overlay? Also, do the updates expose a measurement timestamp, or should we record callback-receipt time when evaluating responsiveness?