简单的SceneKit场景显示黑屏而不是SCNPlane

Question

我正在尝试使用iOS SceneKit，但是以下示例代码（在viewDidLoad内执行）的行为不符合预期。我想要它

1. 将相机放置在原点，方向为正z轴
2. 在z = 100
处放置一个与xy平面平行的红色矩形

为什么渲染不显示红色矩形而只显示黑屏？

    let scene = SCNScene()

    // prepare camera

    let camera = SCNCamera()
    camera.zNear =  90
    camera.zFar  = 110

    let cameraNode = SCNNode()
    cameraNode.position = SCNVector3Make(0, 0, 0)
    cameraNode.rotation = SCNVector4Make(1, 0, 0, Float(M_PI))
    cameraNode.camera   = camera

    scene.rootNode.addChildNode(cameraNode)

    // prepare light

    let light = SCNLight()
    light.type  = SCNLightTypeOmni
    light.color = SKColor(white: 0.3, alpha: 1.0)

    let lightNode = SCNNode()
    lightNode.light = light;

    scene.rootNode.addChildNode(lightNode)

    // prepare plane

    let plane = SCNPlane(width: 400, height: 400)
    plane.firstMaterial!.doubleSided      = true
    plane.firstMaterial!.diffuse.contents = UIColor.redColor().CGColor

    let planeNode = SCNNode(geometry: plane)
    planeNode.position = SCNVector3Make(0, 0, 100)

    scene.rootNode.addChildNode(planeNode)

    // prepare view as SCNView

    let sceneView = view as SCNView

    sceneView.backgroundColor  = SKColor.blackColor()
    sceneView.scene            = scene
    sceneView.delegate         = self
    sceneView.jitteringEnabled = true // i.e. improve visual rendering
    sceneView.pointOfView      = cameraNode

Answer 1

看起来像围绕x轴而不是y轴旋转（以便相机看起来朝向所需方向）