From 4d9b4c3f5742a5cd5c2d13dc117263c762a4b854 Mon Sep 17 00:00:00 2001
From: Nick Lockwood <nick@charcoaldesign.co.uk>
Date: Sun, 28 Jan 2024 23:10:11 +0000
Subject: [PATCH] Allow material passthrough for RealityKit models

---
 Sources/Euclid+RealityKit.swift | 58 ++++++++++++++++++++++++++++++++-
 Tests/RealityKitTests.swift     |  2 +-
 2 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/Sources/Euclid+RealityKit.swift b/Sources/Euclid+RealityKit.swift
index 73ae0c3f..ffed6878 100644
--- a/Sources/Euclid+RealityKit.swift
+++ b/Sources/Euclid+RealityKit.swift
@@ -35,6 +35,15 @@ import CoreGraphics
 import Metal
 import RealityKit
 
+@available(macOS 10.15, iOS 13.0, *)
+private class MaterialWrapper: NSObject {
+    let material: RealityKit.Material
+
+    init(_ material: Material) {
+        self.material = material
+    }
+}
+
 // MARK: export
 
 @available(macOS 10.15, iOS 13.0, *)
@@ -53,6 +62,8 @@ public extension RealityKit.Transform {
 @available(macOS 12.0, iOS 15.0, *)
 private func defaultMaterialLookup(_ material: Polygon.Material?) -> RealityKit.Material? {
     switch material {
+    case let wrapper as MaterialWrapper:
+        return wrapper.material
     case let color as Color:
         return defaultMaterialLookup(OSColor(color))
     case let color as OSColor:
@@ -383,7 +394,52 @@ private extension Mesh {
     ///   - component: The `ModelComponent` to convert into a mesh.
     ///   - materialLookup: An optional closure to map the RealityKit materials to Euclid materials.
     init(_ component: ModelComponent, materialLookup: RealityKitMaterialProvider?) {
-        let materialLookup = materialLookup ?? { _ in nil }
+        let materialLookup = materialLookup ?? {
+            switch $0 {
+            case let simpleMaterial as SimpleMaterial:
+                var material = SimpleMaterial()
+                material.color = simpleMaterial.color
+                material.roughness = simpleMaterial.roughness
+                material.metallic = simpleMaterial.metallic
+                return MaterialWrapper(material)
+            case let unlitMaterial as UnlitMaterial:
+                var material = UnlitMaterial()
+                material.color = unlitMaterial.color
+                material.opacityThreshold = unlitMaterial.opacityThreshold
+                material.blending = unlitMaterial.blending
+                return MaterialWrapper(material)
+            case let occlusionMaterial as OcclusionMaterial:
+                let material = OcclusionMaterial(receivesDynamicLighting: occlusionMaterial.receivesDynamicLighting)
+                return MaterialWrapper(material)
+            case let videoMaterial as VideoMaterial:
+                guard let avPlayer = videoMaterial.avPlayer else { return nil }
+                return MaterialWrapper(VideoMaterial(avPlayer: avPlayer))
+            case let pbrMaterial as PhysicallyBasedMaterial:
+                var material = PhysicallyBasedMaterial()
+                material.baseColor = pbrMaterial.baseColor
+                material.metallic = pbrMaterial.metallic
+                material.roughness = pbrMaterial.roughness
+                material.emissiveColor = pbrMaterial.emissiveColor
+                material.emissiveIntensity = pbrMaterial.emissiveIntensity
+                material.specular = pbrMaterial.specular
+                material.clearcoat = pbrMaterial.clearcoat
+                material.clearcoatRoughness = pbrMaterial.clearcoatRoughness
+                material.opacityThreshold = pbrMaterial.opacityThreshold
+                material.faceCulling = pbrMaterial.faceCulling
+                material.blending = pbrMaterial.blending
+                material.normal = pbrMaterial.normal
+                material.ambientOcclusion = pbrMaterial.ambientOcclusion
+                material.anisotropyLevel = pbrMaterial.anisotropyLevel
+                material.anisotropyAngle = pbrMaterial.anisotropyAngle
+                material.sheen = pbrMaterial.sheen
+                material.textureCoordinateTransform = pbrMaterial.textureCoordinateTransform
+                material.secondaryTextureCoordinateTransform = pbrMaterial.secondaryTextureCoordinateTransform
+                return MaterialWrapper(material)
+            default:
+                // Not supported
+                return nil
+            }
+        }
         self.init(component.mesh, materials: component.materials.map { materialLookup($0) })
     }
 }
diff --git a/Tests/RealityKitTests.swift b/Tests/RealityKitTests.swift
index 1765d213..5ab5a39c 100644
--- a/Tests/RealityKitTests.swift
+++ b/Tests/RealityKitTests.swift
@@ -49,7 +49,7 @@ class RealityKitTests: XCTestCase {
         XCTAssertEqual(part.textureCoordinates?.count, 24)
         let result = Mesh(modelEntity)
         XCTAssertEqual(result.polygons.count, 12)
-        XCTAssertEqual(cube, result)
+        XCTAssertEqual(cube, result.replacing(result.materials[0], with: nil))
     }
 }