How to correct ARFaceAnchor negati… | Apple Developer Forums

How to correct ARFaceAnchor negative Z position

Hello,

I am using ARkit for face tracking with the Truth Depth camera. However, after reading this post https://github.com/Unity-Technologies/arfoundation-samples/issues/288#issuecomment-661634964 and https://stackoverflow.com/questions/57582930/why-does-arfaceanchor-have-negative-z-position

I noticed that ARFaceAnchor is actually left-handed instead of right-handed as the documentation described.

Currently I have:

Code Block extension ViewController: ARSCNViewDelegate {
    
    func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) {
        guard let faceAnchor = anchor as? ARFaceAnchor else { return }
        currentFaceAnchor = faceAnchor
        if node.childNodes.isEmpty, let contentNode = selectedContentController.renderer(renderer, nodeFor: faceAnchor) {
            node.addChildNode(contentNode)
        }
        selectedContentController.session = sceneView?.session
        selectedContentController.sceneView = sceneView
    }
    
    /// - Tag: ARFaceGeometryUpdate
    func renderer(_ renderer: SCNSceneRenderer, didUpdate node: SCNNode, for anchor: ARAnchor) {
        guard anchor == currentFaceAnchor,
            let contentNode = selectedContentController.contentNode,
            contentNode.parent == node
            else { return }
        selectedContentController.session = sceneView?.session
        selectedContentController.sceneView = sceneView
        selectedContentController.renderer(renderer, didUpdate: contentNode, for: anchor)
    }
}

I am wondering how to correct it using the following suggestion from SO:

Code Block func faceAnchorPoseToRHS(_ mat: float4x4) -> float4x4 {
		let correctedPos = float4(x: mat.columns.3.x, y: mat.columns.3.y, z: -mat.columns.3.z, w: 1)
		let quat = simd_quatf(mat)
		let newQuat = simd_quatf(angle: -quat.angle, axis: float3(quat.axis.x, quat.axis.y, -quat.axis.z))
		var newPose = float4x4(newQuat)
		newPose.columns.3 = correctedPos
		return newPose
}

Code Block
func faceAnchorPoseToRHS(_ mat: float4x4) -> float4x4 {
let correctedPos = float4(x: mat.columns.3.x, y: mat.columns.3.y, z: -mat.columns.3.z, w: 1)

let quat = simd_quatf(mat)
let newQuat = simd_quatf(angle: -quat.angle, axis: float3(quat.axis.x, quat.axis.y, -quat.axis.z))
var newPose = float4x4(newQuat)
newPose.columns.3 = correctedPos

return newPose
}

Sorry I am a bit new to ARkit and wondering how to properly use the suggestion above to correct the coordinate system.