Add plane nodes to ARKit scene vertically and horizontally - ios

Question

I want my app to lay the nodes on the surface, which can be vertical or horizontal. However, the node is always vertical. Here's a pic, these nodes aren't placed correctly.
#objc func didTapAddButton() {
let screenCentre = CGPoint(x: self.sceneView.bounds.midX, y: self.sceneView.bounds.midY)
let arHitTestResults: [ARHitTestResult] = sceneView.hitTest(screenCentre, types: [.featurePoint]) // Alternatively, we could use '.existingPlaneUsingExtent' for more grounded hit-test-points.
if let closestResult = arHitTestResults.first {
let transform: matrix_float4x4 = closestResult.worldTransform
let worldCoord: SCNVector3 = SCNVector3Make(transform.columns.3.x, transform.columns.3.y, transform.columns.3.z)
if let node = createNode() {
sceneView.scene.rootNode.addChildNode(node)
node.position = worldCoord
}
}
}
func createNode() -> SCNNode? {
guard let theView = myView else {
print("Failed to load view")
return nil
}
let plane = SCNPlane(width: 0.06, height: 0.06)
let imageMaterial = SCNMaterial()
imageMaterial.isDoubleSided = true
imageMaterial.diffuse.contents = theView.asImage()
plane.materials = [imageMaterial]
let node = SCNNode(geometry: plane)
return node
}
The app is able to see the ground but the nodes are still parallel to us. How can I fix this?
Edit: I figured I can use node.eulerAngles.x = -.pi / 2, this makes sure that the plane is laid down horizontally but it's still horizontal on vertical surfaces as well.

Answer 1

Solved! Here's how to make the view "parallel" to the camera at all times:
let yourNode = SCNNode()
let billboardConstraint = SCNBillboardConstraint()
billboardConstraint.freeAxes = [.X, .Y, .Z]
yourNode.constraints = [billboardConstraint]
Or
guard let currentFrame = sceneView.session.currentFrame else {return nil}
let camera = currentFrame.camera
let transform = camera.transform
var translationMatrix = matrix_identity_float4x4
translationMatrix.columns.3.z = -0.1
let modifiedMatrix = simd_mul(transform, translationMatrix)
let node = SCNNode(geometry: plane)
node.simdTransform = modifiedMatrix