我在一个SceneKit中有两个对象。一个是地球,另一个是月球。它们都位于x:0,y:0,z:0并且重叠。我应该如何改变月球的坐标,使它绕地球?
这里的代码:
import UIKit
import SceneKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let scene = SCNScene()
let cameraNode = SCNNode()
cameraNode.camera = SCNCamera()
cameraNode.position = SCNVector3(x:0, y:0, z:10)
scene.rootNode.addChildNode(cameraNode)
let lightNode = SCNNode()
lightNode.light = SCNLight()
lightNode.light?.type = .directional
lightNode.position = SCNVector3(x:0, y:0, z:2)
scene.rootNode.addChildNode(lightNode)
let stars = SCNParticleSystem(named: "StarsParticles.scnp", inDirectory: nil)!
scene.rootNode.addParticleSystem(stars)
let moonNode = MoonNode()
scene.rootNode.addChildNode(moonNode)
let sceneview = self.view as! SCNView
sceneview.scene = scene
let earthNode = EarthNode()
scene.rootNode.addChildNode(earthNode)
let sceneView = self.view as! SCNView
sceneView.scene = scene
sceneView.showsStatistics = false
sceneView.backgroundColor = UIColor.black
sceneView.allowsCameraControl = true
}
override var prefersStatusBarHidden: Bool {
return true
}
}
你可以让你的视图控制器成为SCNSceneRendererDelegate
,并实现委托方法renderer:willRenderScene
,它给你一个time
。基于那个time
,你可以设置这样的东西:
moonNode.position = SCNVector3(r * cos(Float(time), r * sin(Float(time)), 0)
其中r
是你的地球节点的半径 - 如果你在编译时不知道这一点,只需在这行上面包含这样的东西:
let r = length(float3(earthNode.boundingBox.max) - float3(earthNode.boundingBox.min))
对于我所包含的导致xy平面旋转的代码,这并不完全准确,但它至少会为r
提供正确的数量级。如果您收到无法找到float3或length的错误,请尝试和import simd
。
如果您对此有任何疑问,请告诉我,因为我是从内存中输入的。
更多信息,请参阅文档:https://developer.apple.com/documentation/scenekit/scnscenerendererdelegate/1523483-renderer
您可以使用simdPivot
实例属性轻松完成。
var simdPivot: simd_float4x4 { get set }
这是一个测试代码:
import SceneKit
class GameViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let scene = SCNScene()
let action = SCNAction.repeatForever(SCNAction.rotate(by: .pi,
around: SCNVector3(0,1,0),
duration: 1))
let earthNode = SCNNode(geometry: SCNSphere(radius: 3.57))
earthNode.geometry?.materials.first?.diffuse.contents = UIColor.blue
scene.rootNode.addChildNode(earthNode)
let moonNode = SCNNode(geometry: SCNSphere(radius: 0.15))
moonNode.geometry?.materials.first?.diffuse.contents = UIColor.yellow
moonNode.simdPivot.columns.3.x = 5
moonNode.runAction(action)
scene.rootNode.addChildNode(moonNode)
let sceneView = self.view as! SCNView
sceneView.scene = scene
sceneView.backgroundColor = UIColor.black
sceneView.allowsCameraControl = true
}
}