Position a SceneKit object in front of SCNCamera's current orientation

Question

I would like to create a new SceneKit node when the user taps the screen, and have it appear directly in front of the camera at a set distance. For testing, this will be a S

Answer 1

(Swift 4)

Hey, you can use this simpler function if you want to put the object a certain position relative to another node (e.g. the camera node) and also in the same orientation as the reference node:

func updatePositionAndOrientationOf(_ node: SCNNode, withPosition position: SCNVector3, relativeTo referenceNode: SCNNode) {
    let referenceNodeTransform = matrix_float4x4(referenceNode.transform)

    // Setup a translation matrix with the desired position
    var translationMatrix = matrix_identity_float4x4
    translationMatrix.columns.3.x = position.x
    translationMatrix.columns.3.y = position.y
    translationMatrix.columns.3.z = position.z

    // Combine the configured translation matrix with the referenceNode's transform to get the desired position AND orientation
    let updatedTransform = matrix_multiply(referenceNodeTransform, translationMatrix)
    node.transform = SCNMatrix4(updatedTransform)
}

If you'd like to put 'node' 2m right in front of a certain 'cameraNode', you'd call it like:

let position = SCNVector3(x: 0, y: 0, z: -2)
updatePositionAndOrientationOf(node, withPosition: position, relativeTo: cameraNode)

Edit: Getting the camera node

To get the camera node, it depends if you're using SCNKit, ARKit, or other framework. Below are examples for ARKit and SceneKit.

With ARKit, you have ARSCNView to render the 3D objects of an SCNScene overlapping the camera content. You can get the camera node from ARSCNView's pointOfView property:

let cameraNode = sceneView.pointOfView

For SceneKit, you have an SCNView that renders the 3D objects of an SCNScene. You can create camera nodes and position them wherever you want, so you'd do something like:

let scnScene = SCNScene()
// (Configure scnScene here if necessary)
scnView.scene = scnScene
let cameraNode = SCNNode()
cameraNode.camera = SCNCamera()
cameraNode.position = SCNVector3(0, 5, 10)  // For example
scnScene.rootNode.addChildNode(cameraNode)

Once a camera node has been setup, you can access the current camera in the same way as ARKit:

let cameraNode = scnView.pointOfView