How to do a hitTest on subnodes of node in sceneView?

Question

I have an ARSceneView and I use the detectionImages to find a plane so I can add nodes based on the Image that I detected.

My Issue is that all the time the view is adding an invisible plane node above the nodes that I have added as subnodes in the "node of my Image" and when I add a TapGestureRecognizer to the sceneView I can't detect the node because it detects the plane. Sometimes it works, but when it adds the plane it doesn't work.

When the plane is on scene my nodes are these

I want my nodes to be like this..

▿ 3 elements - 0 : | no child> - 1 : SCNNode: 0x1c41f4100 | light= - 2 : SCNNode: 0x1c43e1000 'DetectableChildrenParent' pos(-0.009494 -0.081575 -0.360098) rot(0.997592 -0.060896 0.033189 1.335512) | 2 children>

and my 2 children to be the detectable nodes only..

but it always is like this

▿ 4 elements - 0 : SCNNode: 0x1c01fcc00 pos(-0.093724 0.119850 -0.060124) rot(-0.981372 0.172364 -0.084866 0.457864) scale(1.000000 1.000000 1.000000) | camera= | no child> - 1 : SCNNode: 0x1c01fc200 | light= | no child> - 2 : SCNNode: 0x1c01fd100 'DetectableChildrenParent' pos(-0.149971 0.050361 -0.365586) rot(0.996908 0.061535 -0.048872 1.379775) scale(1.000000 1.000000 1.000000) | 2 children> - 3 : SCNNode: 0x1c01f9f00 | geometry= | no child>

and it always detect the last node.

My code to detect is this

@objc func addNodeToScene(withGestureRecognizer recognizer: UIGestureRecognizer) {
            let tapLocation = recognizer.location(in: self.sceneView)
            let hitTestResults = sceneView.hitTest(tapLocation)
            if let node = hitTestResults.first?.node {
                    print(node.name ?? "")
            }
    }

How can I run the hit test to check only the children of the DetectableChildrenParent?

Answer 1

Assuming I have interpreted your question correctly, what you are looking for is the childNodes property of the SCNHitTestResult Node which refers to:

An array of the node’s children in the scene graph hierarchy.

As such I believe you can try something like this:

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

    //1. Get The Current Touch Location
    guard let currentTouchLocation = touches.first?.location(in: self.augmentedRealityView),

        //2. Get The Tapped Node From An SCNHitTest
        let hitTestResultNode = self.augmentedRealityView.hitTest(currentTouchLocation, options: nil).first?.node else { return }

    //3. Loop Through The ChildNodes
    for node in hitTestResultNode.childNodes{

        //4. If The Node Has A Name Then Print It Out
        if let validName = node.name{
             print("Node\(validName) Is A Child Node Of \(hitTestResultNode)")
        }

    }

}

Alternatively instead of looking for the 1st result of the SCNHitTest you could try by looking for the last one instead e.g:

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

    //1. Get The Current Touch Location
    guard let currentTouchLocation = touches.first?.location(in: self.augmentedRealityView),

        //2. Get The Tapped Node From An SCNHitTest
        let hitTestResultNode = self.augmentedRealityView.hitTest(currentTouchLocation, options: nil).last?.node else { return }

    //3. Loop Through The ChildNodes
    for node in hitTestResultNode.childNodes{

        //4. If The Node Has A Name Then Print It Out
        if let validName = node.name{
             print("Node\(validName) Is A Child Node Of \(hitTestResultNode)")
        }

    }

}

If you are looking for the children of a specific SCNNode you use the following:

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

    //1. Get The Current Touch Location
    guard let currentTouchLocation = touches.first?.location(in: self.augmentedRealityView),

    //2. Get The Tapped Node From An SCNHitTest
    let hitTestResultNode = self.augmentedRealityView.hitTest(currentTouchLocation, options: nil).first?.node else { return }

    //3. If The Name Of The Nodes Is Equal To DetectableChildrenParent Then Get The Children
    if hitTestResultNode.name == "DetectableChildrenParent"{

        let childNodes = hitTestResultNode.childNodes

        print(childNodes)
    }

}

Or alternatively you can be to simply loop through the SCNHitTestResults like so:

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

    //1. Get The Current Touch Location
    guard let currentTouchLocation = touches.first?.location(in: self.augmentedRealityView) else { return }

    //2. Get The Results Of The SCNHitTest
    let hitTestResults = self.augmentedRealityView.hitTest(currentTouchLocation, options: nil)


    //3. Loop Through Them And Handle The Result
    for result in hitTestResults{

        print(result.node)
        print(result.node.childNodes)
    }


}

Hope it helps...