Strange behavior with SceneKit Node - ios

Question

I created a circular array objects, no problems.
When I rotate there appears to be a sinc or gaussian function at the center.
The camera is a z 60, radius of structure is 30.
Initial view, no artifacts
Rotated 90 deg up, no artifacts
Rotated 180 deg, artifact appears in center of object
Continued rotation, artifact is still there.
The code for the object is here
class func Build(scene: SCNScene) -> SCNNode {
let radius: Double = 30.0
let numberOfStrands: Int = 24
//Create the base chromosomes.
let baseChromosome = SCNBox(width: 4.0, height: 24, length: 1.0, chamferRadius: 0.5)
let baseChromosomes = DNA.buildCircleOfObjects(baseChromosome, numberOfItems: numberOfStrands, radius: radius)
baseChromosomes.position = SCNVector3(x: 0, y: 0.5, z: 0)
return baseChromosomes
}
class func buildCircleOfObjects(_geometry: SCNGeometry, numberOfItems: Int, radius: Double) -> SCNNode {
var x: Double = 0.0
var z: Double = radius
let theta: Double = (M_PI) / Double(numberOfItems / 2)
let incrementalY: Double = (M_PI) / Double(numberOfItems) * 2
let nodeCollection = SCNNode()
nodeCollection.position = SCNVector3(x: 0, y: 0.5, z: 0)
for index in 1...numberOfItems {
x = radius * sin(Double(index) * theta)
z = radius * cos(Double(index) * theta)
let node = SCNNode(geometry: _geometry)
node.position = SCNVector3(x: Float(x), y: 0, z:Float(z))
let rotation = Float(incrementalY) * Float(index)
node.rotation = SCNVector4(x: 0, y: 1, z: 0, w: rotation)
nodeCollection.addChildNode(node)
}
return nodeCollection
}
}

Answer 1

Using these settings
cameraNode.camera?.xFov = 60
cameraNode.camera?.yFov = 60
cameraNode.camera?.zFar = 1000
cameraNode.camera?.zNear = 0.01
the artifacts disappeared. I think this is a problem with zFar, it should have clipped the back surface uniformly not like a lens aberration.

Answer 2

Falling out of Viewing frustum may be the one to cause most problem. However there is another common cause by misunderstanding the behavior of SCNView's allowsCameraControl, that is when you Pinch to zoom in or zoom out (change the camera's fieldOfView), but the pointOfView's position reminds the same.
Your nodes still stand BEHIND the pointOfView, however small the camera's zNear is. Hence you see them got clipped. The code below may help you in this case, at least avoid the problem.
sceneView.pointOfView!.simdPosition
= float3(0, 0, -scene.rootNode.boundingSphere.radius)