swift SceneKit object is empty - swift

Question

im trying to show a earth model on screen, loaded model from here (tried and other same models), but id didn't show on screen
[let scene = SCNScene(named: "tierra-1.obj")
if scene == nil {
print("nuuuul")
return
}
// 2: Add camera node
let cameraNode = SCNNode()
cameraNode.camera = SCNCamera()
// 3: Place camera
cameraNode.position = SCNVector3(x: 0, y: 0, z: 0)
// 4: Set camera on scene
scene?.rootNode.addChildNode(cameraNode)
// 5: Adding light to scene
let lightNode = SCNNode()
lightNode.light = SCNLight()
lightNode.light?.type = .omni
lightNode.position = SCNVector3(x: 0, y: 0, z: 0)
scene?.rootNode.addChildNode(lightNode)
// 6: Creating and adding ambien light to scene
let ambientLightNode = SCNNode()
ambientLightNode.light = SCNLight()
ambientLightNode.light?.type = .ambient
ambientLightNode.light?.color = UIColor.darkGray
scene?.rootNode.addChildNode(ambientLightNode)
// If you don't want to fix manually the lights
sceneView.autoenablesDefaultLighting = true
// Allow user to manipulate camera
sceneView.allowsCameraControl = true
// Show FPS logs and timming
sceneView.showsStatistics = true
// Set background color
sceneView.backgroundColor = UIColor.white
// Allow user translate image
sceneView.cameraControlConfiguration.allowsTranslation = false
// Set scene settings
sceneView.scene = scene][2]
but after loading I have empty screen (example), how to fix that?

Answer 1

I copied and ran your code using a custom obj, I got it loaded and in the viewport.
I loaded in an obj, using a node, and not trying to load the obj as the scene itself.
I noticed that your camera is at world space 0,0,0. that would most likely be inside the mesh, which would appear see through as materials are defaulted with backface culling on.
I assign the material to be blue, just to make it easier to spot incase the asset is very small. I would suggest selecting the asset in XCode, and you can see the bounding box size. This will help get a better idea for how far away you need to move the camera to get it to see the mesh.
import ModelIO
import SceneKit
import SceneKit.ModelIO
import PlaygroundSupport
let scene = SCNScene()
let sceneView = SCNView(frame: CGRect(x:0, y:0, width:800, height:800))
// Set scene settings
sceneView.scene = scene
// 2: Add camera node
let cameraNode = SCNNode()
cameraNode.camera = SCNCamera()
// 3: Place camera
cameraNode.position = SCNVector3(x: 0, y: 0, z: 10)
// 4: Set camera on scene
scene.rootNode.addChildNode(cameraNode)
// Material
let blueMaterial = SCNMaterial()
blueMaterial.diffuse.contents = UIColor.blue
// Accessing the Playground resource folder
let path = Bundle.main.path(forResource:"randomAsset", ofType: "obj")
let asset = MDLAsset(url: URL(string: path!)!)
let object = asset.object(at: 0)
let objNode = SCNNode(mdlObject: object)
objNode.geometry?.materials = [blueMaterial]
scene.rootNode.addChildNode(objNode)
// Allow user to manipulate camera
sceneView.allowsCameraControl = true
// Show FPS logs and timming
//sceneView.showsStatistics = true
// Set background color
sceneView.backgroundColor = UIColor.gray
// Allow user translate image
sceneView.cameraControlConfiguration.allowsTranslation = true
PlaygroundPage.current.setLiveView(sceneView)

Answer 2

I dont think SceneKit supporst loading an Obj as a scene. They currently only allow types that have the ability to export scene data eg.camera,lights. https://developer.apple.com/documentation/scenekit/scnscenesource
If you want to load the obj file you will have to import it into your scene.
This post should help https://forums.developer.apple.com/thread/3979