swift SceneKit 对象为空

Question

我试图在屏幕上显示地球模型，从 here 加载模型（尝试过和其他相同的模型），但 id 没有显示在屏幕上

[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]

但加载后我的屏幕是空的 (example)，如何解决？

Answer 1

我使用自定义 obj 复制并运行了您的代码，我将其加载并在视口中。

我使用节点加载了一个 obj，而不是尝试将 obj 作为场景本身加载。

我注意到您的相机位于世界空间 0,0,0。这很可能在网格内部，因为材质默认启用了背面剔除，所以网格看起来是透明的。

我将材质指定为蓝色，以便在资产非常小的情况下更容易发现。我建议在 XCode 中选择资产，您可以看到边界框大小。这将有助于更好地了解您需要将相机移动多远才能看到网格。

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

我认为 SceneKit 不支持将 Obj 作为场景加载。它们目前只允许能够导出场景数据的类型，例如相机、灯光。 https://developer.apple.com/documentation/scenekit/scnscenesource

如果你想加载 obj 文件，你必须将它导入到你的场景中。 这篇文章应该可以帮助https://forums.developer.apple.com/thread/3979