シーンキットの3D空間で重力を特定のポンツに向ける方法は？

Question

SceneKitを使用して、私はSCNphysicsFieldを使って線代数を作成する方法を知っています。私の質問は、3D空間（例えば、球の中心）の特定の点に向かう方向を指定できるかどうかです。

は、ここで私はradialGravity()と試みているものです：

let gravityNode=SCNNode() 
let gravity=SCNPhysicsField.radialGravity() 
gravity.scope=SCNPhysicsFieldScope.insideExtent 
gravity.strength=9.8 
gravityNode.physicsField=gravity 
gravityNode.position=SCNVector3Make(0, 0, 0) 
homeScene.rootNode.addChildNode(gravityNode) 

Answer 1

使用SCNPhysicsField.radialGravity()。また、影響を受けたい各オブジェクトにフィジックスのボディを配置する必要があります（場合によってはカテゴリのビットマスク）。

ここMacOSの遊び場で実行できるサンプルです：あなたの答えのための

 
//: Playground - noun: a place where people can play 

import Cocoa 
import SceneKit 
import SpriteKit 
import PlaygroundSupport 

let scene = SCNScene() 

let gravityNode = SCNNode() 
let radialGravityField = SCNPhysicsField.radialGravity() 
gravityNode.physicsField = radialGravityField 
gravityNode.position = SCNVector3Make(0, 10, 0) 
radialGravityField.strength = 9.8 

// comment out the next line to disable the radial gravity field 
scene.rootNode.addChildNode(gravityNode) 
// uncomment the next line to disable default gravity 
//scene.physicsWorld.gravity = SCNVector3Make(0, 0, 0) 

let boxGeometry = SCNBox(width: 1, height: 1, length: 1, chamferRadius: 0) 
boxGeometry.firstMaterial?.diffuse.contents = SKColor.yellow 
let shape = SCNPhysicsShape(geometry: boxGeometry, options: nil) 

let boxNode1 = SCNNode(geometry: boxGeometry) 
boxNode1.position = SCNVector3Make(0, 6, 0) 
scene.rootNode.addChildNode(boxNode1) 
let body1 = SCNPhysicsBody(type: .dynamic, shape: shape) 
boxNode1.physicsBody = body1 

let boxNode2 = SCNNode(geometry: boxGeometry) 
boxNode2.position = SCNVector3Make(0, 14, 0) 
scene.rootNode.addChildNode(boxNode2) 
let body2 = SCNPhysicsBody(type: .dynamic, shape: shape) 
boxNode2.physicsBody = body2 

let pyramidNode = SCNNode(geometry: SCNPyramid(width: 1, height: 1, length: 1)) 
pyramidNode.position = SCNVector3Make(2, 10, -2) 
pyramidNode.physicsBody = SCNPhysicsBody(type: .dynamic, shape: SCNPhysicsShape(geometry: pyramidNode.geometry!)) 
scene.rootNode.addChildNode(pyramidNode) 

// put something down at ground level to trick the automatic camera 
let sphereNode = SCNNode(geometry: SCNSphere(radius: 0.2)) 
sphereNode.position = SCNVector3Make(0, -1, 0) 
scene.rootNode.addChildNode(sphereNode) 

let floor = SCNFloor() 
let floorNode = SCNNode(geometry: floor) 
floorNode.physicsBody = SCNPhysicsBody(type: .static, shape: SCNPhysicsShape(geometry: floor, options: nil)) 
scene.rootNode.addChildNode(floorNode) 

let sceneView = SCNView(frame: CGRect(x: 0, y: 0, width: 600, height: 400)) 
sceneView.allowsCameraControl = true 
sceneView.autoenablesDefaultLighting = true 
sceneView.backgroundColor = SKColor.lightGray 
sceneView.showsStatistics = true 
sceneView.debugOptions = [.showPhysicsFields, .showPhysicsShapes] 
PlaygroundPage.current.liveView = sceneView 
sceneView.scene = scene