我正在使用SceneKit的physicsBody系统来检测对象之间的碰撞，并获得一些非常奇怪的结果。为了说明，我有一个最小的例子，它产生两个带有运动物理实体的球体，并将它们以直线移动，以便它们短暂重叠。
我希望看到physicsWorld（：didBeginContact :)只调用一次，当球体首次重叠时，physicsWorld（：didEndContact :)在它们停止重叠时调用一次。相反，我看到每个函数被调用了25次！
以下是重现的代码：在Xcode 8.0中，使用“Game”模板创建一个全新的项目。用以下代码替换GameViewController.swift的内容：
import UIKit
import SceneKit
class GameViewController: UIViewController, SCNSceneRendererDelegate, SCNPhysicsContactDelegate {
var scnScene: SCNScene!
var scnView: SCNView!
var cameraNode: SCNNode!
var nodeA: SCNNode!
var nodeB: SCNNode!
var countBeginnings: Int = 0
var countEndings: Int = 0
override func viewDidLoad() {
super.viewDidLoad()
setupScene()
setupNodes()
}
func setupScene() {
// create a new SCNScene and feed it to the view
scnView = self.view as! SCNView
scnScene = SCNScene()
scnView.scene = scnScene
// assign self as SCNView delegate to get access to render loop
scnView.delegate = self
// assign self as contactDelegate to handle collisions
scnScene.physicsWorld.contactDelegate = self
// create the camera and position it at origin
cameraNode = SCNNode()
cameraNode.camera = SCNCamera()
cameraNode.position = SCNVector3Zero
scnScene.rootNode.addChildNode(cameraNode)
// tell scnView to update every frame
scnView.isPlaying = true
}
func setupNodes() {
// create two spheres with physicsBodies, one inside the other
nodeA = SCNNode()
nodeA.name = "Node A"
nodeA.geometry = SCNSphere(radius: 1.0)
nodeA.geometry!.firstMaterial?.diffuse.contents = UIColor.yellow.withAlphaComponent(0.6)
// expected behavior
// nodeA.position = SCNVector3(x: 0.0, y: -0.8, z: -10.0)
// weird behavior
nodeA.position = SCNVector3(x: 0.0, y: -0.9, z: -10.0)
nodeA.physicsBody = SCNPhysicsBody(type: .kinematic, shape: SCNPhysicsShape(geometry: nodeA.geometry!, options: nil))
scnScene.rootNode.addChildNode(nodeA)
nodeB = SCNNode()
nodeB.name = "Node B"
nodeB.geometry = SCNSphere(radius: 0.5)
nodeB.geometry!.firstMaterial?.diffuse.contents = UIColor.red
nodeB.position = SCNVector3(x: -2.0, y: 0.0, z: -10.0)
nodeB.physicsBody = SCNPhysicsBody(type: .kinematic, shape: SCNPhysicsShape(geometry: nodeB.geometry!, options: nil))
scnScene.rootNode.addChildNode(nodeB)
// node A can collide with node B but not the other way around
nodeA.physicsBody!.categoryBitMask = 2
nodeB.physicsBody!.categoryBitMask = 1
nodeA.physicsBody!.contactTestBitMask = 1
}
func physicsWorld(_ world: SCNPhysicsWorld, didBegin contact: SCNPhysicsContact) {
countBeginnings += 1
print("(" + String(countBeginnings) + ") " + contact.nodeA.name! + " began contact with " + contact.nodeB.name!)
}
func physicsWorld(_ world: SCNPhysicsWorld, didEnd contact: SCNPhysicsContact) {
countEndings += 1
print("(" + String(countEndings) + ") " + contact.nodeA.name! + " ended contact with " + contact.nodeB.name!)
}
var frameNumber = 0
func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) {
nodeB.position.x += 0.01
nodeB.position.y -= 0.01
}
}
还有其他奇怪的事情发生了。如果我稍微改变其中一个球体的初始位置，将y位置从-0.9移动到-0.8：
nodeA.position = SCNVector3(x: 0.0, y: -0.8, z: -10.0)
现在我得到了预期的行为，一个电话开始，一个电话结束！稍微不同的碰撞角度会导致完全不同的行为。
这可能是一个SceneKit错误，还是这实际上是预期的行为？
答案 0 :(得分：1)
SCNRenderer在每一帧运行物理模拟，调用renderer(_:didSimulatePhysicsAtTime:)的SCNSceneRendererDelegate方法。
在两个球体交叉的过程中，将会渲染几个帧，每次运行物理模拟时，都会检测到碰撞。
这是预期的。由你来处理碰撞并将两个球体置于不再碰撞的状态。例如，在游戏中，一旦射弹击中玩家，它就会消失。碰撞被处理，因此不再发射。
我使用XCode版本8.0 beta 5（8S193k）作为OS X应用程序以下列方式使用您的代码。我在控制台中看到以下跟踪。 begin和end方法只调用一次！
(1) Node A began contact with Node B
(1) Node A ended contact with Node B
import SceneKit
import QuartzCore
class GameViewController: NSViewController, SCNSceneRendererDelegate, SCNPhysicsContactDelegate {
@IBOutlet weak var gameView: GameView!
// MARK: Properties
var cameraNode: SCNNode!
var nodeA: SCNNode!
var nodeB: SCNNode!
var countBeginnings: Int = 0
var countEndings: Int = 0
// MARK: Initialization
override func awakeFromNib(){
super.awakeFromNib()
// create a new scene
let scene = SCNScene(named: "art.scnassets/scene.scn")!
// create and add a camera to the scene
let cameraNode = SCNNode()
cameraNode.camera = SCNCamera()
scene.rootNode.addChildNode(cameraNode)
// place the camera
cameraNode.position = SCNVector3(x: 0, y: 0, z: 15)
// create and add a light to the scene
let lightNode = SCNNode()
lightNode.light = SCNLight()
lightNode.light!.type = SCNLightTypeOmni
lightNode.position = SCNVector3(x: 0, y: 10, z: 10)
scene.rootNode.addChildNode(lightNode)
// create and add an ambient light to the scene
let ambientLightNode = SCNNode()
ambientLightNode.light = SCNLight()
ambientLightNode.light!.type = SCNLightTypeAmbient
ambientLightNode.light!.color = NSColor.darkGray
scene.rootNode.addChildNode(ambientLightNode)
// set the scene to the view
self.gameView!.scene = scene
// allows the user to manipulate the camera
self.gameView!.allowsCameraControl = true
// show statistics such as fps and timing information
self.gameView!.showsStatistics = true
// configure the view
self.gameView!.backgroundColor = NSColor.black
self.gameView!.delegate = self
setupScene()
setupNodes()
}
func setupScene() {
// assign self as contactDelegate to handle collisions
self.gameView!.scene?.physicsWorld.contactDelegate = self
// create the camera and position it at origin
cameraNode = SCNNode()
cameraNode.camera = SCNCamera()
cameraNode.position = SCNVector3Zero
self.gameView!.scene?.rootNode.addChildNode(cameraNode)
// tell scnView to update every frame
self.gameView.isPlaying = true
}
func setupNodes() {
// create two spheres with physicsBodies, one inside the other
nodeA = SCNNode()
nodeA.name = "Node A"
nodeA.geometry = SCNSphere(radius: 1.0)
nodeA.geometry!.firstMaterial?.diffuse.contents = NSColor.yellow.withAlphaComponent(0.6)
nodeA.position = SCNVector3(x: 0.0, y: -0.8, z: -10.0)
nodeA.physicsBody = SCNPhysicsBody(type: .kinematic, shape: SCNPhysicsShape(geometry: nodeA.geometry!, options: nil))
self.gameView!.scene?.rootNode.addChildNode(nodeA)
nodeB = SCNNode()
nodeB.name = "Node B"
nodeB.geometry = SCNSphere(radius: 0.5)
nodeB.geometry!.firstMaterial?.diffuse.contents = NSColor.red
nodeB.position = SCNVector3(x: -2.0, y: 0.0, z: -10.0)
nodeB.physicsBody = SCNPhysicsBody(type: .kinematic, shape: SCNPhysicsShape(geometry: nodeB.geometry!, options: nil))
self.gameView!.scene?.rootNode.addChildNode(nodeB)
// node A can collide with node B but not the other way around
nodeA.physicsBody!.categoryBitMask = 2
nodeB.physicsBody!.categoryBitMask = 1
nodeA.physicsBody!.contactTestBitMask = 1
}
// MARK: SCNPhysicsContactDelegate
func physicsWorld(_ world: SCNPhysicsWorld, didBegin contact: SCNPhysicsContact) {
countBeginnings += 1
print("(" + String(countBeginnings) + ") " + contact.nodeA.name! + " began contact with " + contact.nodeB.name!)
}
func physicsWorld(_ world: SCNPhysicsWorld, didEnd contact: SCNPhysicsContact) {
countEndings += 1
print("(" + String(countEndings) + ") " + contact.nodeA.name! + " ended contact with " + contact.nodeB.name!)
}
// MARK: SCNSceneRendererDelegate
var frameNumber = 0
func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) {
nodeB.position.x += 0.01
nodeB.position.y -= 0.01
}
}