SceneKit - Ignore touches on an SCNNode in the foreground and transfer touch to a background node

Question

I am trying to make an app where users can measure distances on an ARSCNView. I have a scenario where there are 2 SCNNodes on top of each other. Node1 is always at the front because of its depth information. Node2 however is useful for measuring and getting accurate measurements. I would like to ignore touches on node1 and only get the location of touch on node2.

When I hide node1, the touches are properly recognized on node2. However, I still need node1 to be visible to the user.

I tried to change the renderingOrder and making sure that node2 is added to the rootNode after node1 is, but was of no success.

I also verified the hitTest array on tapping on a point, only the one hitTest on node1 is recognized and present in the array. So I'm not able to select a different hitTestResult either.

Further info: Node1 is a huge node which occupies a large space and node2 is formed from multiple child nodes.

Answer 1

You could probably do this using different Bitmasks (the categoryBitmask of the SCNNode) on which perform the hitTestResult.

Or if you have physicsBodies involved on the SCNNodes, you can do a rayTest to its physics categoryBitmasks. (scene.physicsWorld.rayTestWithSegment)

Answer 2

Thanks @ZAY for your answer. It worked perfectly.

I got further help from this answer.

What I did:

struct NodeType: OptionSet {
  let rawValue: Int

  static let `default` = NodeType(rawValue: 1)
  static let userInteraction = NodeType(rawValue: 4)
}

My foreground node has a default category bitmask of 1. I did not specify anything.

To my background node, I assigned bitmask as:

node.categoryBitMask = NodeType.userInteraction.rawValue

When performing hitTest, I provided this bitMask as an option:

let touchPosition = gesture.location(in: arSceneView)
let hitResults = arSceneView.hitTest(touchPosition, options: [SCNHitTestOption.categoryBitMask: NodeType.userInteraction.rawValue])

Voila, my foreground node is ignored and the background node gets the hitTest interaction.