xcode - SceneKit Update Method for Physics Simulation -

i have played sprite kit , have used update method set things process each time step. i'm trying learn swift scene kit , can't seem find equivalent.

can point me example of implementing update method scenekit? thanks.

(yes, know question scenekit, not spritekit, touches on commonalities , differences between 2 frameworks, i'll address in answer.)

in spritekit, game-loop methods (update, didsimulatephysics, etc) part of scene class skscene. isn't best idea, though — might want treat scene instance more data place implement game logic (especially scenes can built in xcode 6 graphical scene editor). in ios 8 , os x yosemite, methods in 2 places. if you're subclassing skscene per-frame game logic, can keep doing that. if you'd rather put code elsewhere, can set delegate on scene, , implement equivalent skscenedelegate methods there.

scenekit has more of separation of concerns. scnscene closer being pure data-model object, , rendering-loop functionality managed view (or other object) responsible displaying scene. typically display scene in scnview — there other classes can render scenes, too, common api found in scnscenerenderer protocol. use delegate property defined protocol set delegate view, , in delegate can implement scnscenerendererdelegate methods participate in key phases of render loop.

the scenekit loop phases correspond directly in spritekit: update: becomes renderer:updateattime:, didevaluateactions: becomes renderer:didapplyanimationsattime: (because includes coreanimation-style animations spritekit-style actions), etc.

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so, scenekit equivalent of spritekit per-frame update method, this:

1. set 1 of custom objects (say, view controller) delegate of scnview instance.

2. in custom class, implement following method:

   func renderer(_ arenderer: scnscenerenderer!, updateattime time: nstimeinterval) {     // per-frame code here } 

or similar other scnscenerendererdelegate methods if per-frame logic needs happen after actions or physics have been processed.