# ARKit

Introduced in iOS 11, and massively improved with basically each new major release (and a few minor releases) since then. Apple has been promoting ARKit heavily, much to the chagrin of developers, who haven’t really found a use case for it apart from the sherlock’d-in-iOS 12 “use ARKit as a ruler”.

As for actually using it, the easiest way is to place an ARView (requires iOS 13) in your view hierarchy, and tell it’s associated session to run with an ARConfiguration.

Be sure to update your info.plist with an appropriate string for NSCameraUsageDescription, e.g.:

<key>NSCameraUsageDescription</key>
<string>ARKit uses the camera</string>


## Integrating with SceneKit

ARView, by default, integrates well with SceneKit, with it also hosting an SCNScene.

### Rending UIViews in SceneKit

You can set a UIView as the contents of a SCNMaterialProperty (specifically, the diffuse material property of the node’s SCNMaterial. This isn’t supported all that well - the view needs to be the view for a UIViewController in order to work, and a number of things don’t work well if you do this. Perhaps in a later iOS version this will be better supported.

## Placing objects relative to the camera

Placing something relative to the camera is done easily enough. Possibly in response to a tap on the view, you first get the transform for the camera is in the scene, and then multiply it by a matrix for where you want the object placed, as well as possibly rotating for whether the device is portrait or landscape. Something like this generates the transform:

guard let camera = self.arView.session.currentFrame?.camera else { return }

var translation = matrix_identity_float4x4
translation.columns.3.z = -1

let rotation = matrix_float4x4(SCNMatrix4MakeRotation(Float.pi/2, 0, 0, 1))

let objectTransform = matrix_multiply(camera.transform, matrix_multiply(translation, rotation))


You then use the objectTransform matrix as the simdWorldTransform of the SCNNode you’re adding to the scene (assuming SceneKit))

## Demos

Made With ARKit is a blog featuring some of the really cool things people have done with ARKit. Sadly, it hasn’t seen an update since December 2017.

Last updated: 2020-09-05 08:08:21 -0700