SCNNode parent-child relationship in SceneKit? - ios

Question

From my former question, I believe cloning the SCNNode is the way to solve the problem of loading multiple objects. However, I realized there is something wrong.
I did something like
arrow = scnScene.rootNode.childNode(withName: "arrow", recursively:true)
arrow.rotation = SCNVector4(0, 0, 1, M_PI_2)
arrow.position = SCNVector3(x: 0, y: 0, z: -3);
let sign = SCNNode()
for i in 0..<10{
let node = arrow.clone()
node.position = SCNVector3(i+1,0,0)
sign.addChildNode(node)
}
arrow.addChildNode(sign)
I expect there is a row of arrows displaying but actually there is a column of arrows (Translating in x axis but in fact affecting y axis, seems cloned node's coordinate system has been changed) displaying and all of child objects rotate 180 degree. Why?
Before Karl Sigiscar told me to use SCNReferenceNode, I am not sure how should I use it and will it achieve my goal?
Update:
I tried SCNReferenceNode like this:
let scnScene = SCNScene()
if let filePath = Bundle.main.path(forResource: "arrowsign", ofType: "dae", inDirectory: "art.scnassets") {
// ReferenceNode path -> ReferenceNode URL
let referenceURL = NSURL(fileURLWithPath: filePath)
if #available(iOS 9.0, *) {
arrow = SCNReferenceNode(url: referenceURL as URL!)!
arrow.load()
arrow.rotation = SCNVector4(0, 0, 1, -M_PI_2)
arrow.position = SCNVector3(0,0,-5)
// Create reference node
for i in 0..<10{
let referenceNode : SCNReferenceNode = SCNReferenceNode(url: referenceURL as URL)!
referenceNode.load()
referenceNode.position = SCNVector3(i+1, 0, 0);
arrow.addChildNode(referenceNode)
}
}
}
scnScene.rootNode.addChildNode(arrow)
I didn't rotate child nodes but they rotated automatically (-M_PI_2 degree) when I run it. And I did translate in x axis but in fact there is a column of arrows displaying, rather than a row of arrows. Is that a feature of child-parent node?

Answer 1

After using SCNReferenceNode, I figured out if you add a node to another node as the child, the child node will be set to the parent node's location. For instance, there is a parent node in location (3,4,5), then all of child nodes of it will be located in (3,4,5) at first (you can modify later). So if you want a row of arrows, just modify child nodes' x and keep y & z value be equal to zero.
If the parent node applies rotation, the rotation will be applied to child nodes as well.