Dragging SCNNode in ARKit Using SceneKit

Question

I have a simple SCNNode in ARKit and I am trying to drag it wherever I moved my finger on the phone. Here is my code.

 @objc func pan(recognizer :UIGestureRecognizer) {

        guard let currentFrame = self.sceneView.session.currentFrame else {
            return
        }

        var translation = matrix_identity_float4x4
        translation.columns.3.z = -1.5

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

        let hitTestResult = sceneView.hitTest(touchLocation, options: [:])

        if !hitTestResult.isEmpty {

            print("hit result")

            guard let hitResult = hitTestResult.first else {
                return
            }

            let node = hitResult.node

            node.simdTransform = matrix_multiply(currentFrame.camera.transform, translation)
        }
    }

The problem is that the drag is very slow and not smooth.

Answer 1

Had the same issue. Using a SCNTransaction did the trick for me.

@objc private func handlePan(_ gesture: UIPanGestureRecognizer) {
    [...]

    SCNTransaction.begin()
    SCNTransaction.animationDuration = 0
    imagePlane.position.x = hitTestResult.localCoordinates.x
    imagePlane.position.y = hitTestResult.localCoordinates.y
    SCNTransaction.commit()
}

Answer 2

I handle translation with PanGesture like this. The division by 700 is to smooth and adjust speed of movement, I reached to that value by trial or error, you may want to experiment with it

@objc func onTranslate(_ sender: UIPanGestureRecognizer) {
    let position = sender.location(in: scnView)
    let state = sender.state

    if (state == .failed || state == .cancelled) {
        return
    }

    if (state == .began) {
        // Check it's on a virtual object
        if let objectNode = virtualObject(at: position) {
            // virtualObject(at searches for root node if it's a subnode
            targetNode = objectNode
            latestTranslatePos = position
        }

    }
    else if let _ = targetNode {

        // Translate virtual object
        let deltaX = Float(position.x - latestTranslatePos!.x)/700
        let deltaY = Float(position.y - latestTranslatePos!.y)/700

        targetNode!.localTranslate(by: SCNVector3Make(deltaX, 0.0, deltaY))

        latestTranslatePos = position

        if (state == .ended) {
            targetNode = nil
        }
    }
}