'Preloading assets in AR with SceneKit
In our AR app and appclip made with SceneKit, we experience very significant drops in framerate when we make our 3D content appear at different steps of the experience. We have conducted our tests on an iPhone X (iOS 15.2.1), on an iPhone 12 Pro (iOS 14), and on an iPad Pro 2020 (iPad OS 14.8.1).
For now, all of our 3D objects are in our Main Scene. Those which are supposed to appear at some point in the experience have their opacity set to 0.01 at the beginning and then fade in with a SCNAction (the reason why we tried setting their opacity to 0.01 at the start was to make sure that these objects are rendered from the start of the experience).
However, if the objects all have their opacity set to 1 from the start of the experience, we do not experience any fps drop.
It is worth noting that the fps drops only happen the first time the app is opened. If I close it and re-open it, then it unfolds without any freeze.
What would be the best way to load (or pre-load) these 3D elements to avoid these freezes?
I have been told the prepareObject:shouldAbortBlock: and the prepareObjects:withCompletionHandler methods could solve our problem.
In our case the SceneView is an ARCNView, so we can't seem to access the SCNSceneRenderer methods. We have only managed to implement the "Prepare" method to preload our assets: https://developer.apple.com/documentation/scenekit/scnscenerenderer/1523375-prepare
It seems to be doing something because we get a significantly longer freeze at the start of the experience, however, we still experience the same fps drops during the experience when our objects appear for the first time.
Is there any documentation on how to use the prepareObject:shouldAbortBlock: and the prepareObjects:withCompletionHandler methods in an ARCNView?
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