ARKit save object position and see it in any next

Question

I am working for a project using ARKit. I need to save an object position and I want to see it in my next application launch where ever it was. For example in my office I attached some text on a door and come back to home and next day I wish to see that text on that place where it was is it possible in ARKit.

Answer 1

In iOS 12: Yes!

"ARKit 2", aka ARKit for iOS 12, adds a set of features Apple calls "world map persistence and sharing". You can take everything ARKit knows about its local environment, including any ARAnchors you're using to track the real-world positions of virtual content, and save it in an ARWorldMap object.

Then you can serialize that object to a file, and load the file later to effectively resume the earlier AR session (if the user is in the same local environment). Upon successfully "relocalizing" to the world map, your session has all the same ARAnchors it did before saving, so you can use that to re-create your virtual content (e.g. use the name of a saved/restored anchor to decide which 3D model to show).

For more info, see the WWDC18 talk on ARKit 2 or Apple's ARKit docs and sample code.

Otherwise, probably not.

Before iOS 12, ARKit doesn’t provide a way to make any results of its local-world mapping persistent. Everything you do, every point you locate, within an AR session is defined only in the context of that session. If you place some virtual content based on plane detection, hit testing, and/or user input, the frame of reference for that position is relative to where your device was at the beginning of the session.

With no frame of reference that can persist across sessions, there’s no way to position virtual content that’ll have it appear to stay in the same real-world position/orientation after (fully) quitting/restarting the app.

But maybe...

One of the additions from “ARKit 1.5” in iOS 11.3 is sort of an escape valve for this problem: image detection. If your app’s use case involves a known/controlled environment (for example, using virtual overlays to guide visitors in an art museum), and there are some easily recognizable 2D features in that environment (like notable paintings), ARKit can detect their positions.

Once you’ve detected an image anchor that you know is a fixed feature of the environment, you can tell your AR Session to redefine its world coordinate system around that anchor (see setWorldOrigin). After doing that, you effectively have a coordinate system that’s the same across multiple sessions (assuming you detect the same image and set the world origin in each session).