How to centre blend shape SCNNode to view

Question

So I'm fairly new to ARKit and SceneKit, and I'm following the tutorial from Apple here. https://developer.apple.com/documentation/arkit/tracking_and_visualizing_faces.

What I'm trying to do is create a view, similar to the Animoji screen, where the SCNNode containing the BlendShape is centred in the view and z value of the Blendshape does not change depending on how close/far the face is from the camera. I'd also like to make the camera invisible so you can only see the BlendShape.

What is the best way of going about this and how?

I've tried setting the pivot to 0 and the position.z to 0 too, but I don't think this is the correct approach.

func renderer(_ renderer: SCNSceneRenderer, didUpdate node: SCNNode, for anchor: ARAnchor) {
        guard let faceAnchor = anchor as? ARFaceAnchor
            else { return }

        let blendShapes = faceAnchor.blendShapes
        guard let eyeBlinkLeft = blendShapes[.eyeBlinkLeft] as? Float,
            let eyeBlinkRight = blendShapes[.eyeBlinkRight] as? Float,
            let jawOpen = blendShapes[.jawOpen] as? Float
            else { return }
        eyeLeftNode.scale.z = 1 - eyeBlinkLeft
        eyeRightNode.scale.z = 1 - eyeBlinkRight
        jawNode.position.y = originalJawY - jawHeight * jawOpen
        node.pivot = SCNMatrix4MakeTranslation(0,0,0)
        node.position.z = 0

    }

A view below is similar to what I'm trying to achieve, without the list of other blendshapes.

mnuages mnuages · Accepted Answer · 2019-08-02T16:26:28

If you're not interested in ARKit automatically moving nodes in the scene you could avoid tying an SCNNode to the ARAnchor (that is don't implement -renderer:nodeForAnchor:). Rather you would query the ARAnchor in -session:didUpdateAnchors:.

In fact since you don't actually have an AR experience, but just face tracking, you don't even need an ARSCNView but just a SCNView.

How to centre blend shape SCNNode to view

1 Answers