Moving SCNNode in ARSCNView using a gesture

Question

I have been trying to use UIPanGestureRecognizer to move an SCNNode attached to a UISceneView in iOS ARKit. It moves fine in the x dimension, but I cannot seem to figure out how to move it in the y direction. I have followed two different approaches, trying each without success:

1. How do I find my mouse point in a scene using SceneKit?

2. https://github.com/rajubd49/ARKit-Sample-ObjC

Any insight on why the y dimension does not seem to behave the same as the x would be greatly appreciated. Could this have something to do with motion only in the XZ plane or something? Here is the code following the GitHub sample code cited in #2 above):

==============

//Move SCNNode - (void)handlePanGesture:(UIPanGestureRecognizer *)pagr {

switch (pagr.state)
{
    case UIGestureRecognizerStateBegan:
    {
        CGPoint tapPoint    =   [pagr locationInView:sceneView];
        NSLog(@"%s tapPoint  %@",__FUNCTION__,NSStringFromCGPoint(tapPoint));

        NSArray *hitResults = [sceneView hitTest:tapPoint types:ARHitTestResultTypeFeaturePoint | ARHitTestResultTypeEstimatedHorizontalPlane];
        lastHitTestResult   =   [hitResults firstObject];
    }
        break;
    case UIGestureRecognizerStateChanged:
    {
        CGPoint tapPoint            =   [pagr locationInView:sceneView];
        if (windScreenView.buttonState == GypsyTargetAdded)
        {
            NSArray *hitResults         =   [sceneView hitTest:tapPoint types:ARHitTestResultTypeFeaturePoint | ARHitTestResultTypeEstimatedHorizontalPlane];
            ARHitTestResult *result     =   [hitResults lastObject];

            [SCNTransaction begin];

            SCNMatrix4 lastMatrix   =   SCNMatrix4FromMat4(lastHitTestResult.worldTransform);
            SCNVector3 lastVector   =   SCNVector3Make(lastMatrix.m41, lastMatrix.m42, lastMatrix.m43);

            SCNMatrix4 newMatrix    =   SCNMatrix4FromMat4(result.worldTransform);
            SCNVector3 newVector        =   SCNVector3Make(newMatrix.m41, newMatrix.m42, newMatrix.m43);
            CGFloat dx              =   newVector.x-lastVector.x;
            CGFloat dy              =   newVector.y-lastVector.y;
            SCNVector3 adjVector        =   SCNVector3Make(gypsyTargetNode.position.x + dx, gypsyTargetNode.position.y + dy, gypsyTargetNode.position.z);
            gypsyTargetNode.position    =   adjVector;

            [SCNTransaction commit];

            NSLog(@"%s lastVector: x = %f, y = %f, z = %f",__FUNCTION__,lastVector.x,lastVector.y,lastVector.z);
            NSLog(@"%s newVector: x = %f, y = %f, z = %f",__FUNCTION__,newVector.x,newVector.y,newVector.z);
            NSLog(@"%s dx = %f, dy = %f",__FUNCTION__,dx,dy);
            NSLog(@"%s gypsyTargetNode.position: x = %f, y = %f, z = %f",__FUNCTION__,gypsyTargetNode.position.x,gypsyTargetNode.position.y,gypsyTargetNode.position.z);
            NSLog(@"%s hitResults.count: %li",__FUNCTION__,hitResults.count);
            lastHitTestResult       =   result;
        }
    }
        break;
    case UIGestureRecognizerStateEnded:
    {
        lastHitTestResult   =   nil;
    }
        break;
    default:
        break;
}

}

and here are snippets of the output console. Note that the calculated "dx" is always .000000 .

[CalibrationController handlePanGesture:] tapPoint  {207.33332824707031, 507}

[CalibrationController handlePanGesture:] lastVector: x = -0.016018, y = -0.083625, z = 0.006696

[CalibrationController handlePanGesture:] newVector: x = -0.015562, y = -0.083862, z = 0.006658

[CalibrationController handlePanGesture:] dx = 0.000456, dy = **-0.000237**

[CalibrationController handlePanGesture:] gypsyTargetNode.position: x = -0.018142, y = -0.087894, z = 0.008041

[CalibrationController handlePanGesture:] hitResults.count: 2

[CalibrationController handlePanGesture:] lastVector: x = -0.015562, y = -0.083862, z = 0.006658

[CalibrationController handlePanGesture:] newVector: x = -0.015562, y = -0.083862, z = 0.006658

[CalibrationController handlePanGesture:] dx = 0.000000, dy = **0.000000**

[CalibrationController handlePanGesture:] gypsyTargetNode.position: x = -0.018142, y = -0.087894, z = 0.008041

[CalibrationController handlePanGesture:] hitResults.count: 2

[CalibrationController handlePanGesture:] lastVector: x = -0.015562, y = -0.083862, z = 0.006658

[CalibrationController handlePanGesture:] newVector: x = -0.015150, y = -0.083862, z = 0.006565

[CalibrationController handlePanGesture:] dx = 0.000412, dy = **0.000000**

[CalibrationController handlePanGesture:] gypsyTargetNode.position: x = -0.017730, y = -0.087894, z = 0.008041

[CalibrationController handlePanGesture:] hitResults.count: 2

[CalibrationController handlePanGesture:] lastVector: x = -0.015150, y = -0.083862, z = 0.006565

[CalibrationController handlePanGesture:] newVector: x = -0.014686, y = -0.083862, z = 0.006361

[CalibrationController handlePanGesture:] dx = 0.000463, dy = **0.000000**

Answer 1

For panning gesture implement the following approach:

let myScene = SCNScene(named: "scene.scn")!
let modelNode: SCNNode = myScene.rootNode
var selectedNode: SCNNode? = nil


override func viewDidLoad() {
    super.viewDidLoad()

    let moveGesture = UIPanGestureRecognizer(target: self, 
                                             action: #selector(moveModel))

    self.sceneView.addGestureRecognizer(moveGesture)
}

Check important conditions if any:

private func myMethod(at position: CGPoint) -> SCNNode? {

    let nnn = self.sceneView.hitTest(position, options: nil).first(where: { 
        $0.node !== modelNode 
    })?.node

    return nnn
}

Fill a gesture recognizer @objc method:

@objc func moveModel(_ gesture: UIPanGestureRecognizer) {

    let location = gesture.location(in: self.sceneView)

    switch gesture.state {
        case .began:
            selectedNode = myMethod(at: location)
        case .changed:
            guard let result = self.sceneView.hitTest(location, 
                                               types: .existingPlane).first 
            else { 
                return 
            }
            let transform = result.worldTransform
            let newPosition = SIMD3<Float>(transform.columns.3.x, 
                                           transform.columns.3.y, 
                                           transform.columns.3.z)
            selectedNode?.simdPosition = newPosition
        default:
            selectedNode = nil
    }
}