Arkit: Placing an Scntext at a Particular Point in Front of the Camera

ARKit: Placing an SCNText at a particular point in front of the camera

The coordinate center for an SCNGeometry is its center point. But when you are creating a SCNText the center point is somewhere in the bottom left corner:

You need to center the text first. This can be done by checking the bounding box of the node containing your text and setting a pivot transform to change the texts center to its actual center:

func center(node: SCNNode) {
    let (min, max) = node.boundingBox

    let dx = min.x + 0.5 * (max.x - min.x)
    let dy = min.y + 0.5 * (max.y - min.y)
    let dz = min.z + 0.5 * (max.z - min.z)
    node.pivot = SCNMatrix4MakeTranslation(dx, dy, dz)
}

Edit:

Also note this answer that explains some additional pitfalls:
A text with 16 pts font size is 16 SceneKit units tall. But in ARKit 1 SceneKit units = 1 meter!

SCNText, containerFrame, wrapping and ARKit

Answer from Apple: my font size was too small. If I use a "normal" font size and containing frame on the SCNText object, and then set a scale on the node that contains it, everything wraps as expected. Something like:

extrudedText.font = UIFont(name: definition.fontname, size: 20)!  
extrudedText.containerFrame = CGRect(origin: .zero, size: CGSize(width: 100.0, height: 500.0))
...
scale = SCNVector3Make(0.01, 0.01, 0.01)

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