RealityKit – Material's Alpha transparency - swift

Question

Is it possible to have alpha transparency with textures?
I have png file that contains 8 bit RGBA, but for some reason, the supposed-to-be-transparent parts are simply black.
I assign the material like this:
private func setupLightMeshes(_ scene: Entity) {
let lightEntity = scene.findEntity(named: "LightWindow_Plane")!
var lightMaterial = UnlitMaterial()
lightMaterial.baseColor = try! MaterialColorParameter.texture(
TextureResource.load(named: "light.png")) // this is 8bpc RGBA
var modelComponent = lightEntity.components[ModelComponent] as! ModelComponent
modelComponent = ModelComponent(mesh: modelComponent.mesh, materials: [lightMaterial])
lightEntity.components.set(modelComponent)
}

Answer 1

RealityKit 1.0
.tintColor is a multiplier for .baseColor
If you have a .png file with a premultiplied alpha (RGB*A). all you need to do is to additionally use a tintColor instance property with alpha equal to 0.9999.
material.tintColor = UIColor(white: 1.0, alpha: 0.9999)
Here's how it looks like in a real code:
fileprivate func material() -> UnlitMaterial {
var material = UnlitMaterial()
material.baseColor = try! .texture(.load(named: "transparent.png"))
material.tintColor = UIColor(white: 1.0, alpha: 0.9999)
return material
}
override func viewDidLoad() {
super.viewDidLoad()
let sphere: MeshResource = .generateSphere(radius: 0.5)
let entity = ModelEntity(mesh: sphere,
materials: [material()])
let anchor = AnchorEntity()
anchor.orientation = simd_quatf(angle: .pi, axis: [0, 1, 0])
anchor.addChild(entity)
arView.scene.anchors.append(anchor)
}
P.S.
For me, it seems like a bug in RealityKit 1.0. I have no clues why method .load(named: "file.png") doesn't work as expected.
RealityKit 2.0
The same story about partially transparent textures is in RealityKit 2.0:
var material = SimpleMaterial()
material.color = try! .init(tint: .white.withAlphaComponent(0.9999),
texture: .init(.load(named: "semi.png", in: nil)))
tint parameter is a multiplier for texture as well.