如何在SceneKit Editor中居中模型的枢轴点

Question

Is there anyway to center the pivot of a model? Currently (by default) it is set to the bottom left. I want to set to the center. How can I do that?

Here is the image:

UPDATE : I added another node and added the chair as a child.

So, now it works better but it does not rotate all the way and it resets the position if I continue to rotate. Here is the code for the panned operation:

  @objc func panned(recognizer :UIPanGestureRecognizer) {

        var newAngleY :Float = 0.0

        if recognizer.state == .changed {

            let sceneView = recognizer.view as! ARSCNView
            let touchPoint = recognizer.location(in: sceneView)
            let translation = recognizer.translation(in: sceneView)

            print(translation.x)

            let scnHitTestResults = self.sceneView.hitTest(touchPoint, options: nil)

            if let hitTestResult = scnHitTestResults.first {

                if let parentNode = hitTestResult.node.parent {

                    newAngleY = (Float)(translation.x)*(Float)(Double.pi)/180
                    newAngleY += currentAngleY
                    parentNode.eulerAngles.y = newAngleY
                }

            }
        }

        else if recognizer.state == .ended {
            currentAngleY = newAngleY
        }

    }

Answer 1

You can change a pivot of the Chair using the pivot property of the SCNNode ( Apple Documentation )

You can change this using an SCNMatrix4MakeTranslation eg:

nodeToAdd.pivot = SCNMatrix4MakeTranslation(0,0,0)

This may solve the problem:

    //1. Get The Bounding Box Of The Node
    let minimum = float3(nodeToAdd.boundingBox.min)
    let maximum = float3(nodeToAdd.boundingBox.max)

    //2. Set The Translation To Be Half Way Between The Vector
    let translation = (maximum - minimum) * 0.5

    //3. Set The Pivot
    nodeToAdd.pivot = SCNMatrix4MakeTranslation(translation.x, translation.y, translation.z)

You could also change it within within a program like Blender or Maya .

Alternatively, and probably much easier , is to edit the model in the SceneKit Editor itself.

If you cant fix it's pivot, then what you can do is to create an Empty Node , and then add the Chair as a child of this, ensuring that it is centered within that.

This way you should be able to transform it's rotation for example more accurately.