How to place a 3D model of type OBJ with ARKit?

Question

I need some help with placing a 3D model with the new apple ARKit. Is it possible to place an object of type OBJ? I'm trying to place a 3d model of a skull.

//Load the OBJ file
let bundle = Bundle.main
guard let url = bundle.url(forResource: "Cranial", withExtension: "obj") else {
    fatalError("Failed to find model file")
}

let asset = MDLAsset(url:url)
guard let object = asset.object(at: 0) as? MDLMesh else {
    fatalError("Failed to get mesh from asset")
}

let scene = SCNScene()
let nodeCranial = SCNNode.init(mdlObject: object)
nodeCranial.simdPosition = float3(0, 0, 0.5)
sceneView.scene.rootNode.addChildNode(nodeCranial)

I don't know why nothing shows up in front of the camera. It works if I use the following line instead of the nodeCranial from above:

let cubeNode = SCNNode(geometry: SCNBox(width: 0.1, height: 0.1, length: 0.1, chamferRadius: 0))

Why doesn't it work for OBJ file too? The code above is in the func viewDidLoad().

How big is your head? 3D assets are often built to arbitrary scale, but in ARKit one unit of scene space maps to one real-world meter. If your OBJ mesh is, say, several tens of units wide, it might not appear the way you want in AR. You can check its size with the boundingBox property at run time or by loading the OBJ file in the scene editor in Xcode. — rickster

Mayuri R Talaviya Mayuri R Talaviya · Accepted Answer · 2018-05-05T12:42:58

    let tempScene = SCNScene(named: "art.scnassets/cat/cat.obj")!
    modelNode = tempScene.rootNode
    modelNode.simdPosition = float3(0, 0, 0.5)
    sceneView.scene.rootNode.addChildNode(modelNode)

you can load .obj, .scn or .dae files like this way.

How to place a 3D model of type OBJ with ARKit?

1 Answers