ios - 如何使用 SceneKit iOS 添加背面图像作为纹理

Question

我是 SceneKit 新手，创建了一个对象，我将图像作为纹理添加到对象中，但它在正面和背面都显示。我想要的是在其后面显示另一个图像。是否可以添加两个纹理为了一个物体？

    let scene = SCNScene()
    var planet : SCNGeometry
    let tempScene = SCNScene(named: "FrameOBJ.obj")
    planet = tempScene!.rootNode.childNodes[0].geometry!
    let material = SCNMaterial()

    let url = URL(string: "www.imageasf.com/123.png")
    let data = try? Data(contentsOf: url!) //make sure your image in this url does exist, otherwise unwrap in a if let check / try-catch
    let image = UIImage(data: data!)

    material.diffuse.contents = image
    material.diffuse.wrapT = SCNWrapMode.mirror
    material.diffuse.wrapS = SCNWrapMode.mirror
    material.isDoubleSided = true
    planet.materials = [material]
    let planetNode = SCNNode(geometry: planet)
    scene.rootNode.addChildNode(planetNode)
    sceneView.cameraControlConfiguration.allowsTranslation = true
    sceneView.allowsCameraControl = true
    sceneView.scene = scene

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Answer 1

我是通过添加 Material 数组来完成的。

    let tempScene = SCNScene(named: "untitled.obj")
    planet = tempScene!.rootNode.childNodes[0].geometry!

    var image = UIImage()
    let url = URL(string: "https://www.images123.jpg")!
    //make sure your image in this url does exist, otherwise unwrap in a if let check / try-catch
    var node = SCNNode()

    do {
        let data = try Data(contentsOf: url)
        image = UIImage(data: data)!
        node = SCNNode(geometry: SCNBox(width: 0.05, height: 1, length:1, chamferRadius: 0.5))
        node.geometry?.firstMaterial?.diffuse.contents = image
        // do something with data
        // if the call fails, the catch block is executed
    } catch {
        print(error.localizedDescription)
    }

    let  allMaterial = SCNMaterial()
    allMaterial.diffuse.contents = UIImage(named: "woods.png")

    let smallMaterial1 = SCNMaterial()
    smallMaterial1.diffuse.contents = image
    node.scale = SCNVector3(0.5,0.5,0.5)
    node.geometry?.materials = [smallMaterial1,allMaterial,smallMaterial1,smallMaterial1,smallMaterial1,smallMaterial1];

    scene.rootNode.addChildNode(node)
    print(node.scale)
    print(scene.rootNode.scale)
    sceneView.cameraControlConfiguration.allowsTranslation = true
    sceneView.allowsCameraControl = true
    sceneView.scene = scene