ARKit how position nodes base on horizon and not the camera orientation?

Question

When I add a new node with ARKit (ARSKView), the object is positioned base on the device camera. So if your phone is facing down or tilted, the object will be in that direction as well. How can I instead place the object base on the horizon?

Answer 1

For that, right after a new node's creation, use a worldOrientation instance property that controls the node's orientation relative to the scene's world coordinate space.

var worldOrientation: SCNQuaternion { get set }

This quaternion isolates the rotational aspect of the node's worldTransform matrix, which in turn is the conversion of the node's transform from local space to the scene's world coordinate space. That is, it expresses the difference in axis and angle of rotation between the node and the scene's rootNode.

let worldOrientation = sceneView.scene.rootNode.worldOrientation

yourNode.rotation = worldOrientation    /*  X, Y, Z, W components  */

P.S. (as you updated your question) :

If you're using SpriteKit, 2D sprites you spawn in ARSKView are always face the camera. So, if the camera moves around a definite point of real scene, all the sprites must be rotated about their pivot point, still facing a camera.

Nothing can prevent you from using SceneKit and SpriteKit together.