Rotate SCNNode then move relative to rotation? - swift

Question

My node setup:
let node = SCNNode()
node.position = SCNVector3(0.0, 0.0, 0.0)
I then wish to rotate the node by 90 degrees to the left which can be achieved with:
node.transform = SCNMatrix4Rotate(node.transform, .pi/2, 0.0, 1.0, 0.0)
Next, I want to translate the node forward one unit along the negative z axis relative to current rotation and end up with:
node.position = SCNVector3(-1.0, 0.0, 0.0)
I have no idea how to get from the rotation of the node to the position of the node programmatically.
Basically node begins at (0, 0, 0), its forward vector is the -z axis, node turns left and moves one unit forward to end up at (-1, 0, 0).
This isn't working:
func move(_ direction: moveDirection) {
switch direction {
case .forward: characterNode.position = SCNVector3(characterNode.position.x, characterNode.position.y, characterNode.position.z - 1.0)
case .left: characterNode.pivot = SCNMatrix4Rotate(characterNode.pivot, -.pi/32, 0.0, 1.0, 0.0)
case .backward: characterNode.position = SCNVector3(characterNode.position.x, characterNode.position.y, characterNode.position.z + 1.0)
case .right: characterNode.pivot = SCNMatrix4Rotate(characterNode.pivot, .pi/32, 0.0, 1.0, 0.0)
}
}

Answer 1

Assuming I have understood you correctly, once you have rotated your SCNNode, you want to move it forward it in that direction.
This can be done by using the worldFront value which is simply:
The local unit -Z axis (0,0,-1) in world space.
As such this may be the answer you are looking for:
//1. Create A Node Holder
let nodeToAdd = SCNNode()
//2. Create An SCNBox Geometry
let nodeGeometry = SCNBox(width: 0.2, height: 0.2, length: 0.2, chamferRadius: 0)
nodeGeometry.firstMaterial?.diffuse.contents = UIColor.cyan
nodeGeometry.firstMaterial?.lightingModel = .constant
nodeToAdd.geometry = nodeGeometry
//3. Position It 1.5m Away From The Camera
nodeToAdd.position = SCNVector3(0, 0, -1.5)
//4. Rotate The Node By 90 Degrees On It's Y Axis
nodeToAdd.rotation = SCNVector4Make(0, 1, 0, .pi / 2)
//5. Add The Node To The ARSCNView
augmentedRealityView.scene.rootNode.addChildNode(nodeToAdd)
//6. Use The World Front To Move The Node Forward e.g
/*
nodeToAdd.simdPosition += nodeToAdd.simdWorldFront * 1.2
*/
nodeToAdd.simdPosition += nodeToAdd.simdWorldFront
//7. Print The Position
print(nodeToAdd.position)
/*
SCNVector3(x: -0.999999881, y: 0.0, z: -1.50000024)
*/