Swift 3 SceneKit - Proper light on custom mesh node - opengl

Question

I'm trying to get a light shining from the camera onto a custom mesh I have created. However, no matter what I do to position a Light Node it always seems to stick to the original pivot point (0,0) of the custom mesh.
This is the code I use for creating my scene, light, camera and mesh nodes, and then finally adding an event handler to rotate the mesh on the x axis.
let scene = SCNScene() //Instantiate Scene for 3D object
SceneView.scene = scene
let ambientLightNode = SCNNode()
ambientLightNode.light = SCNLight()
ambientLightNode.light!.type = SCNLight.LightType.ambient
ambientLightNode.light!.color = UIColor(white: 0.67, alpha: 1.0)
scene.rootNode.addChildNode(ambientLightNode)
let omniLightNode = SCNNode()
omniLightNode.light = SCNLight()
omniLightNode.light!.castsShadow = true
omniLightNode.light!.type = SCNLight.LightType.omni
omniLightNode.light!.color = UIColor(white: 0.75, alpha: 1.0)
omniLightNode.position = SCNVector3Make(0, 0, 0)
scene.rootNode.addChildNode(omniLightNode)
let cameraNode = SCNNode()
cameraNode.camera = SCNCamera()
cameraNode.position = SCNVector3Make(0, 2, 0)
scene.rootNode.addChildNode(cameraNode)
//Create the mesh node.
let environmentMeshNode = SCNNode()
environmentMeshNode.position = SCNVector3Make(0, 0, -8)
scene.rootNode.addChildNode(environmentMeshNode)
//Create the custom mesh, move pivot point and add material.
environmentMesh.geometry = EnvironmentMesh.createEnvironmentMesh(10, 10)
environmentMesh.pivot = SCNMatrix4MakeTranslation(4.5, 0.5, -4.5)
environmentMesh.geometry?.firstMaterial?.diffuse.contents = UIColor.gray
environmentMeshNode.addChildNode(environmentMesh)
//Adding recognisers to manipulate rotation on x axis.
let panXRecognizer = UIPanGestureRecognizer(target: self, action: #selector(self.rotateXGesture(_:)))
SceneView.addGestureRecognizer(panXRecognizer)
The gestureRecognizer then rotate the mesh in the following way:
func rotateXGesture (_ sender: UIPanGestureRecognizer) { //X rotation recognizer
let translation = sender.translation(in: sender.view)
var newXAngle = (Float)(translation.x)*(Float)(Double.pi)/180.0
newXAngle += currentXAngle
environmentMesh.transform = SCNMatrix4MakeRotation(newXAngle, 0, 1, 0)
if(sender.state == UIGestureRecognizerState.ended){
currentXAngle = newXAngle
}
}
This is the class used for creating the custom mesh which is in this case just a 10x10 grid where a few vertices are elevated slightly.
class EnvironmentMesh{
//Custom function for creating the plane mesh. Takes in mesh vertex arguments.
static func createEnvironmentMesh(_ xSize: Int, _ zSize: Int) -> SCNGeometry {
var vertices:[SCNVector3] = []
for x in stride(from:0, to:xSize, by:1){
for z in stride(from:0, to:-zSize, by:-1) { // Creates a X*Y square of vertices.
vertices.append(SCNVector3Make(Float(x), 0, Float(z)))
}
}
vertices[55].y = 5
vertices[27].y = 3
vertices[85].y = 2
vertices[58].y = 1.3
let vertexData = NSData(bytes: vertices, length: vertices.count * MemoryLayout<SCNVector3>.size)
let vertexSource = SCNGeometrySource(data: vertexData as Data, semantic: SCNGeometrySource.Semantic.vertex, vectorCount: vertices.count, usesFloatComponents: true, componentsPerVector: 3, bytesPerComponent: MemoryLayout<Float>.size, dataOffset: 0, dataStride: MemoryLayout<SCNVector3>.size)
let normalSource = SCNGeometrySource(data: vertexData as Data, semantic: SCNGeometrySource.Semantic.normal, vectorCount: vertices.count, usesFloatComponents: true, componentsPerVector: 3, bytesPerComponent: MemoryLayout<Float>.size, dataOffset: 0, dataStride: MemoryLayout<SCNVector3>.size)
var indices:[Int32] = []
for x in stride(from:0, to:xSize-1, by:1){
for z in stride(from:0, to: zSize-1, by:1){
indices.append(Int32((x * 10) + z)) //0
indices.append(Int32(((x + 1) * 10) + z)) //10
indices.append(Int32((x * 10) + (z + 1))) //1
indices.append(Int32((x * 10) + (z + 1))) //1
indices.append(Int32(((x + 1) * 10) + z)) //10
indices.append(Int32(((x + 1) * 10) + (z + 1))) //11
}
}
let indexData = NSData(bytes: indices, length: MemoryLayout<Int32>.size * indices.count)
let indexElement = SCNGeometryElement(data: indexData as Data, primitiveType: SCNGeometryPrimitiveType.triangles, primitiveCount: indices.count / 3, bytesPerIndex: MemoryLayout<CInt>.size)
let geometry = SCNGeometry(sources: [vertexSource, normalSource], elements: [indexElement])
return geometry
}
}
This is my first questions here, I hope I have provided the needed information, else. Please let me know.