Stopping and then re-starting a `SKSpriteNode` not behaving when moving along the bottom half of an oval UIBezierPath Works great when moving along top half; just the bottom half that produces a problem.

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Stopping and then re-starting a SKSpriteNode not behaving when moving along the bottom half of an oval UIBezierPath Works great when moving along top half; just the bottom half that produces a problem.

Code works with the train moving along the top half of the oval; i.e., the train stops and restarts where it previously stopped and the train images remain in-tact.

But, along bottom half, multiple cars all squeezed together and train cars don’t restart where I stopped them.

Here are hopefully the required code snippets = (using @DonMag’s brilliant Ellipse code)

Path creation:

func createTrainPath() {
    
    trainRect = CGRect(x: tracksPosX - tracksWidth/2,
                       y: tracksPosY - tracksHeight/2,
                       width: tracksWidth,
                       height: tracksHeight)

    trainPoints = generatePoints(inRect: trainRect,
                                 withNumberOfPoints: nbrPathPoints)
    trainPath = generatePathFromPoints(trainPoints!,
                                       startingAtIDX: savedTrainIndex)
            
}   // createTrainPath

Start and Resume movement code:

func resumeFollowTrackPaths() {
    
    // Resets each Path based on each saved,,Index
    // when previously stopped.
    gameScene.setGameNodePaths()
    // Now, resume where we left off at saved..Index.
    startFollowTrackPaths()
    
}   // resumeFollowTrackPaths

func setGameNodePaths() {
    
    // delete any old Paths before creating new ones:
    itsGameViewController.deleteBezierPaths()
    
    itsGameViewController.createTrainPath()   // + the cars

}   // setGameNodePaths

func startFollowTrainPath() {
                   
    var trainAction = SKAction.follow(trainPath.cgPath,
                                      asOffset: false,
                                      orientToPath: true,
                                      speed: thisSpeed)
    trainAction = SKAction.repeatForever(trainAction)
    myTrain.run(trainAction, withKey: runTrainKey)

}   // startFollowTrainPath

Stop movement code:

func stopFollowTrainPath() {
    
    guard (myTrain != nil) else { return }

    myTrain.removeAction(forKey: runTrainKey)

    savedTrainPosition = myTrain.position
    savedTrainIndex = closestIndexInPath(
                                  trainPath,
                                  toPoint: savedTrainPosition) ?? 0

}   // stopFollowTrainPath

GameScene’s update(..) code (from John at Apple DTS + @DonMag):

override func update(_ currentTime: TimeInterval) {
    
    super.update(currentTime)

    let t = myTrain.position
    if t.y < trainPath.bounds.midY && trainIsOnTopOfOval
    {
        trainIsOnTopOfOval = false

        itsGameViewController.stopAnimatedTrain()
        // Thanks, John - DTS
        itsGameViewController.initAnimatedTrainHere("bottom")
        itsGameViewController.startAnimatedTrain()
        
        // set orientation of each car = that of myTrain
        myCoalcar.texture = coalcarBottom
        myFreightcar.texture = freightcarBottom
        myBaggagecar.texture = baggagecarBottom
    }
    else if t.y > trainPath.bounds.midY && !trainIsOnTopOfOval
    {
        trainIsOnTopOfOval = true

        itsGameViewController.stopAnimatedTrain()
        itsGameViewController.initAnimatedTrainHere("top")
        itsGameViewController.startAnimatedTrain()
        
        // set orientation of each car = that of myTrain
        myCoalcar.texture = coalcarTop
        myFreightcar.texture = freightcarTop
        myBaggagecar.texture = baggagecarTop            
    }

}   // update

As stated above, code works with the train moving along the top half of the oval; i.e., the train stops and restarts where it previously stopped and the train images remain in-tact.

Code goes south when train moving along bottom half of the oval. Not 100% certain, but I think the problem surfaces when I re-create the BezierPath starting at the stopped Index. Just a wild guess at this point.

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