Adding child nodes to terraine nodes on ARSCNView

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I have tried a good few different combinations but once I'm on ARSCNView I can't seem to add any child nodes. Even If I don't use terrainNode.convertPosition and just try to add a child to the root node, nothing shows.

The child is being added as if I check the count of arView?.scene.rootNode.childNodes it is increasing every time I add a child node but visually I see nothing.

I am adding them like this with a button once everything loaded:

`
let endSphere = SCNNode(geometry: SCNSphere(radius: 100.0))
endSphere.geometry?.firstMaterial?.diffuse.contents = UIColor.red
endSphere.position = (arView?.scene.rootNode.position)!

arView?.scene.rootNode.addChildNode(endSphere)

print(arView?.scene.rootNode.childNodes.count)`

Start at the ARSCNView setup and the button callback that creates the SCNSphere, then inspect how the scene rootNode, terrainNode.convertPosition, camera, and node transforms are configured. The issue is resolved when a red sphere added to the scene is visibly rendered and its child-node count still updates as expected.

Written by the indexing model from the issue text.