How to show metallic and transparent textures in SceneKit? - swift

Question

I have trouble showing some textures in SceneKit, this is the model I would like to use:
Model in Sketchfab : https://skfb.ly/6QVTQ
The model should appear in these colors and textures in the AR environment using Scene Kit. But the golden tips appear black and the transparent lenses do not appear at all. Are there any suggestions to solve this problem?
The model is .scn format. here is the the model materials properties:
https://drive.google.com/file/d/1HIHEsyONLXyL95dcSy9xWMGX89udMPND/view?usp=sharing
https://drive.google.com/file/d/1ndrZfcjqIQ4d2OfG6ZNvwyfDXnihJbnH/view?usp=sharing
If you need any additional information please let me know.
Thank you in advance.

Answer 1

There's no photorealistic glass with true index of refraction (IoR) in SceneKit but you can easily create a fake one using phong shader. Phong shader also has three important properties of a glass – specularity, reflectivity, and fresnelExponent.
For metallic material use physicallyBased shading model.
Here's a code:
import SceneKit
class ViewController: NSViewController {
override func viewDidLoad() {
super.viewDidLoad()
let sceneView = self.view as! SCNView
sceneView.scene = SCNScene(named: "glasses.scn")!
sceneView.allowsCameraControl = true
sceneView.pointOfView?.position.z = 20
let glassesFrame = sceneView.scene?.rootNode.childNode(withName: "glassesFrame",
recursively: true)
glassesFrame?.geometry?.firstMaterial?.lightingModel = .physicallyBased
glassesFrame?.geometry?.firstMaterial?.metalness.intensity = 1
glassesFrame?.geometry?.firstMaterial?.diffuse.contents = NSColor.systemBrown
let lens1 = sceneView.scene?.rootNode.childNode(withName: "rightLens",
recursively: true)
let lens2 = sceneView.scene?.rootNode.childNode(withName: "leftLens",
recursively: true)
let material = SCNMaterial()
material.lightingModel = .phong
material.diffuse.contents = NSColor(white: 0.2,
alpha: 1)
material.diffuse.intensity = 0.9
material.specular.contents = NSColor(white: 1,
alpha: 1)
material.specular.intensity = 1.0
material.reflective.contents = NSImage.Name("art.scnassets/texture.png")
material.reflective.intensity = 2.0
material.transparencyMode = .dualLayer
material.fresnelExponent = 2.2
material.isDoubleSided = true
material.blendMode = .alpha
material.shininess = 100
material.transparency.native = 0.7
material.cullMode = .back
lens1?.geometry?.firstMaterial = material
lens2?.geometry?.firstMaterial = material
}
}