How to measure horizontal plane surface(visible in camera) using ARKit-Scenekit before placing objects?

2
votes

I want to measure the horizontal plane surface to find whether it fits the object that i am going to place. For ex. if i am going to place a cot 3D model(with fixed size) in a room using iOS 11 ARKit,

First i want to detect if that room surface is sufficient or not to place my 3D model by measuring the surface area(width and height etc.)

Second if the user tries to place it without sufficient place, i should not allow him to place the cot and show him error message.

I created a sample POC by following https://developer.apple.com/sample-code/wwdc/2017/PlacingObjects.zip using which i am able to detect the horizontal plane and place the cot. But the issue is whatever may be the surface, user is able to place the cot which shouldn't be allowed in real time.

I saw couple of demos in which they say we can measure the size of the room or a horizontal plane(https://www.curbed.com/2017/6/29/15894556/ar-measure-app-augmented-reality-ruler-measuring-tape-ios)

I am using ARKit Scenekit inorder to achieve this and i am new to AR and Scenekit. I need to know if this is doable, and if so how to achieve it.

1
scenekitios11xcode9-betaarkit
Are you able to solve this? if you can please share your solution for this? – Hiren
Not exactly. I followed what rickster suggested. Create a border and let user decide whether it fits or not. No luck on detecting the obstacles in surface. – yaali

1 Answers

1
votes

You could estimate the size of a detected plane by inspecting its dimensions. But you shouldn't.

ARKit has plane estimation, not scene reconstruction. That is, it'll tell you there's a flat surface at (some point) and that said surface probably extends at least (some distance) from that point. It doesn't know exactly how big the surface is (it's even refining its estimate over time), and it doesn't tell you where there are interruptions in that continuous surface, much less the size and shape of such interruptions.

In fact, if you're looking at the floor and moving around, and you see one patch of floor, then another patch of floor on the other side of a solid wall from the first, ARKit will happily recognize that those two patches are coplanar and merge them into the same anchor. At the same time, neither detected patch may cover the entire extent of the floor around it.

If you attempt to restrict where the user can place virtual objects in AR based on plane estimates, you're likely to frustrate them with two kinds of error: you'll have areas where it looks to the user like they can place something but that don't allow it, and you'll have areas that look like they should be off-limits that do allow placing things.

Instead, design your experience to involve the user in deciding where the sensible places for content are. See this demo for example — ARKit detects the level of the floor (not its boundaries), then uses that to show UI indicating the size/shape of objects to be placed. It's up to the user to make sure there's enough room for the couch, etc.

As for the technical how-to on what you probably shouldn't do: The docs for ARPlaneAnchor.extent say that the x and z coordinates of that vector are the width and length of the estimated plane. And all units in ARKit are meters. (Which is width and which is length? It's a matter of perspective. And of the rotation encoded in the anchor's transform.)