SCNBillboardConstraint isn’t working. Node with constraint doesn’t change - ios

Question

Perhaps I am not setting up the camera properly… I’m starting with a scn file with a camera. In Xcode, rotating the free camera around, the geometries rotate as expected. However, at runtime, nothing happens.
It doesn’t seem to matter if I add the constraint in code or in the editor. The look at constraint works.
It also doesn’t seem to matter if I use the camera from the scn file or if I add a camera in code.
The sample code is
class Poster: SCNNode {
let match:GKTurnBasedMatch
init(match:GKTurnBasedMatch, width:CGFloat, height:CGFloat) {
self.match = match
super.init()
// SCNPlane(width: width, height: height)
self.geometry = SCNBox(width: width, height: height, length: 0.1, chamferRadius: 0)
self.constraints = [SCNBillboardConstraint()]
self.updatePosterImage()
}
}

Answer 1

So… I gave up on the billboard constraint.
I’m using a SCNLookAtConstraint that looks at the camera node, with the gimbal lock enabled.
I was using a SCNPlane but it was doing weird stuff. So I went with a SCNBox for the geometry.
So, in the constructor:
self.geometry = SCNBox(width: self.size.width, height: self.size.height, length: 0.1, chamferRadius: 0)
let it = SCNLookAtConstraint(target: cameraNode)
it.isGimbalLockEnabled = true
self.constraints = [it]
It works.

Answer 2

You're missing ".init()" on the SCNBillboardConstraint(). This line alone did all the work for me:
node.constraints = [SCNBillboardConstraint.init()]

Answer 3

Try this:
A constraint that orients theNode to always point toward the current camera.
// Create the constraint
SCNBillboardConstraint *aConstraint = [SCNBillboardConstraint billboardConstraint];
theNode.constraints = #[aConstraint];
theNode is the node you want pointing to the camera. This should work.
Updated
Ok, if you were to create a sample Project with the Game template. And then make the following changes:
// create a clone of the ship, change position and rotation
SCNNode *ship2 = [ship clone];
ship2.position = SCNVector3Make(0, 4, 0);
ship2.eulerAngles = SCNVector3Make(0, M_PI_2, 0);
[scene.rootNode addChildNode:ship2];
// Add the constraint to `ship`
SCNBillboardConstraint *aConstraint = [SCNBillboardConstraint billboardConstraint];
ship.constraints = #[aConstraint];
ship is constrained but ship2 isn't.
If you were to add this:
ship2.constraints = #[aConstraint];
Now, both will face the camera. Isn't this what you are looking for?

Answer 4

By any chance are you using the allowsCameraControl property on SCNView?
If so, remember setting that will add a new camera to your scene (cloning an existing camera if one is present to match its settings), so if you create a constraint to your own camera, the constraint will not be linked to the camera that’s actually being used.
Per Apple in their WWDC 2017 video, they say that property is really for debugging purposes, not for a real-world use.
Simply put, you have to ensure you are moving around your own camera, not relying on the auto-created one.