How to split out multiple animations from Collada file in SceneKit

Question

I am loading a third-party .dae Collada file as a scene into a SceneKit project.

The .dae file has many different animations in it, set at different times/frames. I

Answer 1

Here is code that converts frame numbers to times and then plays only that portion of the animation by using a CAAnimationGroup as @Toyos described. This sample code plays an "idle" animation by repeating frames 10 through 160 of fullAnimation:

func playIdleAnimation() {
    let animation = subAnimation(of:fullAnimation, startFrame: 10, endFrame: 160)
    animation.repeatCount = .greatestFiniteMagnitude
    addAnimation(animation, forKey: "animation")
}

func subAnimation(of fullAnimation:CAAnimation, startFrame:Int, endFrame:Int) -> CAAnimation {
    let (startTime, duration) = timeRange(startFrame:startFrame, endFrame:endFrame)
    let animation = subAnimation(of: fullAnimation, offset: startTime, duration: duration)
    return animation
}

func subAnimation(of fullAnimation:CAAnimation, offset timeOffset:CFTimeInterval, duration:CFTimeInterval) -> CAAnimation {
    fullAnimation.timeOffset = timeOffset
    let container = CAAnimationGroup()
    container.animations = [fullAnimation]
    container.duration = duration
    return container
}

func timeRange(startFrame:Int, endFrame:Int) -> (startTime:CFTimeInterval, duration:CFTimeInterval) {
    let startTime = timeOf(frame:startFrame)
    let endTime = timeOf(frame:endFrame)
    let duration = endTime - startTime
    return (startTime, duration)
}

func timeOf(frame:Int) -> CFTimeInterval {
    return CFTimeInterval(frame) / framesPerSecond()
}

func framesPerSecond() -> CFTimeInterval {
    // number of frames per second the model was designed with
    return 30.0
}