ARKit(SceneKit) 更新模型臉部表情

1. 使用包含BlendShapes的模型。如sample的fbx模型
2. 在Blender中匯入fbx模型，確認Object Data Properties有外形鍵
   
   
   
3. 匯出成dae檔，確認有勾選外形鍵
   
   
   
4. 使用ColladaMorphAdjuster將剛剛的dae檔，轉成SceneKit支援的dae檔
5. 在XCode中，可以看到模型的Attributes裡，Geometry Morphers中會有類似臉部細心的key
   
   
   
6. Editor -> convert to SceneKit file format
7. 載入模型

   func renderer(_ renderer: SCNSceneRenderer, nodeFor anchor: ARAnchor) -> SCNNode? {

       if anchor is ARFaceAnchor {

           let scene = SCNScene(named: "art.scnassets/POLYWINK_BOD_157_SAMPLE.scn")!

           face = scene.rootNode.childNode(withName: "POLYWINK_Louise", recursively: true)

           face?.geometry?.firstMaterial?.lightingModel = .physicallyBased

           return scene.rootNode

       } else {

           return nil

       }

   }

8. 將BlendShapesLocation對照到模型的外形鍵

   let blendShapeMap: [ARFaceAnchor.BlendShapeLocation: String] = [

       .eyeBlinkLeft: "Eye_Closed_Left",

       .eyeBlinkRight: "Eye_Closed_Right"

   ]

9. 將faceAnchor的blendShapes對照到node的morpher

   func renderer(_ renderer: SCNSceneRenderer, didUpdate node: SCNNode, for anchor: ARAnchor) {

       if let faceAnchor = anchor as? ARFaceAnchor {

           let blendShapes = faceAnchor.blendShapes

           blendShapeMap.forEach{ key, name in

               if let weight = blendShapes[key] as? CGFloat {

                   face?.morpher?.setWeight(weight, forTargetNamed: name)

               }

           }

       }

   }