SceneKit SCNPhysics车辆车轮指向车辆中心
SceneKit SCNPhysicsVehicle wheels point toward centre of vehicle
我正在尝试获取 SceneKit 物理载具 demonstration from WWDC working using Swift 2 and also the Scene Editor and .scnassets. I'm adapting this port of the demo to Swift 1.
我也一直在试验模型 I/O 的一些功能，例如天空盒和法线贴图生成。
一切正常，除了车轮绕其转向轴旋转 180 度，以便轮毂盖指向汽车的中心：
轮毂罩向内
车轮打滑方向正确，车子可以很好的行驶和转向，但就是看起来很奇怪（而且左右轴距比应有的窄）。
如果我注释掉 SCNPhysicsVehicle 和 SCNPhysicsVehicleWheel 代码，那么它只是带有底盘物理体的几何体，几何体显示正确，轮毂指向外：
轮毂罩朝外
我试过在定义 SCNPhysicsVehicleWheel 之前使用 wheelnode0.rotation 旋转轮节点，但没有效果。
我尝试用 wheel0.axle = SCNVector3(x: 1,y: 0,z: 0) 反转轮轴，这使得车轮朝向正确的方向，轮毂罩向外，（并且它们仍然以正确的方式旋转），但是汽车向后移动（即相反的方向轮子是如何旋转的）。
感觉坐标轴的翻译方式有点奇怪，但我不知道是什么。我已经尝试使用 Apple 演示中的原始 .dae 模型，并转换为 .scn 文件。我已经在 .scnassets 文件夹的内部和外部尝试过它（以防它与 scnassets 向上轴的自动更正有关）。我尝试反转车轮转向轴，但这只会导致车轮在空中指向上方。
这是我的车辆创建函数，我尝试过的所有内容都被注释掉了。完整的回购协议在这里：https://github.com/Utsira/SCNPhysicsVehicle-test。谁能看到这里出了什么问题？提前致谢。
func setupCar() -> SCNNode {
let carScene = SCNScene(named: "art.scnassets/rc_car.scn") //rc_car.dae
let chassisNode = carScene!.rootNode.childNodeWithName("rccarBody", recursively: true)!
chassisNode.position = SCNVector3Make(0, 10, 30)
//chassisNode.rotation = SCNVector4(0, 1, 0, CGFloat(M_PI))
let body = SCNPhysicsBody.dynamicBody()
body.allowsResting = false
body.mass = 80
body.restitution = 0.1
body.friction = 0.5
body.rollingFriction = 0
chassisNode.physicsBody = body
scnScene.rootNode.addChildNode(chassisNode)
//getNode("rccarBody", fromDaePath: "rc_car.dae")
let wheelnode0 = chassisNode
.childNodeWithName("wheelLocator_FL", recursively: true)!
let wheelnode1 = chassisNode
.childNodeWithName("wheelLocator_FR", recursively: true)!
let wheelnode2 = chassisNode
.childNodeWithName("wheelLocator_RL", recursively: true)!
let wheelnode3 = chassisNode
.childNodeWithName("wheelLocator_RR", recursively: true)!
//wheelnode0.geometry!.firstMaterial!.emission.contents = UIColor.blueColor()
// SCNTransaction.begin()
// wheelnode0.rotation = SCNVector4(x: 0, y: 1, z: 0, w: Float(M_PI)) //CGFloat(M_PI)
// wheelnode1.rotation = SCNVector4(x: 0, y: 1, z: 0, w: Float(M_PI))
// wheelnode2.rotation = SCNVector4(x: 0, y: 1, z: 0, w: Float(M_PI))
// wheelnode3.rotation = SCNVector4(x: 0, y: 1, z: 0, w: Float(M_PI))
// SCNTransaction.commit()
// wheelnode0.eulerAngles = SCNVector3Make(0, Float(M_PI), 0 )
let wheel0 = SCNPhysicsVehicleWheel(node: wheelnode0)
let wheel1 = SCNPhysicsVehicleWheel(node: wheelnode1)
let wheel2 = SCNPhysicsVehicleWheel(node: wheelnode2)
let wheel3 = SCNPhysicsVehicleWheel(node: wheelnode3)
// wheel0.steeringAxis = SCNVector3Make(0, -1, 1) //wheels point up in the air with 0,1,0
// wheel1.steeringAxis = SCNVector3Make(0, -1, 1)
// wheel2.steeringAxis = SCNVector3Make(0, -1, 1)
// wheel3.steeringAxis = SCNVector3Make(0, -1, 1)
//
// wheel0.axle = SCNVector3(x: 1,y: 0,z: 0) //wheels face and spin the right way, but car moves in opposite direction with 1,0,0
// wheel1.axle = SCNVector3(x: 1,y: 0,z: 0)
// wheel2.axle = SCNVector3(x: 1,y: 0,z: 0)
// wheel3.axle = SCNVector3(x: 1,y: 0,z: 0)
// wheel0.steeringAxis = SCNVector3()
// var min = SCNVector3(x: 0, y: 0, z: 0)
// var max = SCNVector3(x: 0, y: 0, z: 0)
// wheelnode0.getBoundingBoxMin(&min, max: &max)
// let wheelHalfWidth = Float(0.5 * (max.x - min.x))
// var w0 = wheelnode0.convertPosition(SCNVector3Zero, toNode: chassisNode)
// w0 = w0 + SCNVector3Make(wheelHalfWidth, 0, 0)
// wheel0.connectionPosition = w0
// var w1 = wheelnode1.convertPosition(SCNVector3Zero, toNode: chassisNode)
// w1 = w1 - SCNVector3Make(wheelHalfWidth, 0, 0)
// wheel1.connectionPosition = w1
// var w2 = wheelnode2.convertPosition(SCNVector3Zero, toNode: chassisNode)
// w2 = w2 + SCNVector3Make(wheelHalfWidth, 0, 0)
// wheel2.connectionPosition = w2
// var w3 = wheelnode3.convertPosition(SCNVector3Zero, toNode: chassisNode)
// w3 = w3 - SCNVector3Make(wheelHalfWidth, 0, 0)
// wheel3.connectionPosition = w3
vehicle = SCNPhysicsVehicle(chassisBody: chassisNode.physicsBody!,
wheels: [wheel0, wheel1, wheel2, wheel3])
scnScene.physicsWorld.addBehavior(vehicle)
return chassisNode
}
我找到了解决方案：
（但不是我希望的解决方案）
我的解决方法是将“FrontLeftWheel”的连接位置调整到最右边，以致于它充当了“FrontRightWheel”的角色。
而“FrontRightWheel”，靠左太多，以至于它扮演了“FrontLeftWheel”的角色。
我也为背部做了这个。
基本上，你有：
SCNVector3Make(wheelHalfWidth, 0, 0)
我将其替换为：
SCNVector3Make(wheelHalfWidth * 5.2, 0, 0)
但是，您可能不得不使用数字“5.2”来匹配您的 COLLADA (.dae)。
注：
别忘了替换：
vehicle = SCNPhysicsVehicle(chassisBody: chassisNode.physicsBody!,
wheels: [wheel0, wheel1, wheel2, wheel3])
有：
vehicle = SCNPhysicsVehicle(chassisBody: chassisNode.physicsBody!,
wheels: [wheel1, wheel0, wheel3, wheel2])
这样，当你使用 car.wheels[0].
你就得到了你期望的轮子
我认为你的问题是你没有为每个轮子设置连接位置。 Apple 的默认 ObjectiveC 代码很难转换为 swift.
wheel0.connectionPosition = SCNVector3FromFloat3(SCNVector3ToFloat3([wheel0Node convertPosition:SCNVector3Zero toNode:chassisNode]) + (vector_float3){wheelHalfWidth, 0.0, 0.0});
wheel1.connectionPosition = SCNVector3FromFloat3(SCNVector3ToFloat3([wheel1Node convertPosition:SCNVector3Zero toNode:chassisNode]) - (vector_float3){wheelHalfWidth, 0.0, 0.0});
wheel2.connectionPosition = SCNVector3FromFloat3(SCNVector3ToFloat3([wheel2Node convertPosition:SCNVector3Zero toNode:chassisNode]) + (vector_float3){wheelHalfWidth, 0.0, 0.0});
wheel3.connectionPosition = SCNVector3FromFloat3(SCNVector3ToFloat3([wheel3Node convertPosition:SCNVector3Zero toNode:chassisNode]) - (vector_float3){wheelHalfWidth, 0.0, 0.0});
翻译这四行（忽略重复）
let wheel0Position = wheel0Node.convertPosition(SCNVector3Zero, to: chassisNode)
let vector0Float3 = vector_float3(wheel0Position.x, wheel0Position.y, wheel0Position.z) + vector_float3(wheelHalfWidth, 0,0)
wheel0.connectionPosition = SCNVector3(vector0Float3.x, vector0Float3.y, vector0Float3.z)
let wheel1Position = wheel1Node.convertPosition(SCNVector3Zero, to: chassisNode)
let vector1Float3 = vector_float3(wheel1Position.x, wheel1Position.y, wheel1Position.z) - vector_float3(wheelHalfWidth, 0,0)
wheel1.connectionPosition = SCNVector3(vector1Float3.x, vector1Float3.y, vector1Float3.z)
let wheel2Position = wheel2Node.convertPosition(SCNVector3Zero, to: chassisNode)
let vector2Float3 = vector_float3(wheel2Position.x, wheel2Position.y, wheel2Position.z) + vector_float3(wheelHalfWidth, 0,0)
wheel2.connectionPosition = SCNVector3(vector2Float3.x, vector2Float3.y, vector2Float3.z)
let wheel3Position = wheel3Node.convertPosition(SCNVector3Zero, to: chassisNode)
let vector3Float3 = vector_float3(wheel3Position.x, wheel3Position.y, wheel3Position.z) - vector_float3(wheelHalfWidth, 0,0)
wheel3.connectionPosition = SCNVector3(vector3Float3.x, vector3Float3.y, vector3Float3.z)
通过添加或减去 vector_float3，轮子定位在正确的位置。
此外，请记住您不能在场景中缩放节点，否则可能会发生奇怪的事情。
遇到同样的问题，我的解决办法是旋转所有轮子节点，使Y轴指向下方。我认为重力是向下的力。
我正在尝试获取 SceneKit 物理载具 demonstration from WWDC working using Swift 2 and also the Scene Editor and .scnassets. I'm adapting this port of the demo to Swift 1.
我也一直在试验模型 I/O 的一些功能，例如天空盒和法线贴图生成。
一切正常，除了车轮绕其转向轴旋转 180 度，以便轮毂盖指向汽车的中心：
车轮打滑方向正确，车子可以很好的行驶和转向，但就是看起来很奇怪（而且左右轴距比应有的窄）。
如果我注释掉 SCNPhysicsVehicle 和 SCNPhysicsVehicleWheel 代码，那么它只是带有底盘物理体的几何体，几何体显示正确，轮毂指向外：
我试过在定义 SCNPhysicsVehicleWheel 之前使用 wheelnode0.rotation 旋转轮节点，但没有效果。
我尝试用 wheel0.axle = SCNVector3(x: 1,y: 0,z: 0) 反转轮轴，这使得车轮朝向正确的方向，轮毂罩向外，（并且它们仍然以正确的方式旋转），但是汽车向后移动（即相反的方向轮子是如何旋转的）。
感觉坐标轴的翻译方式有点奇怪，但我不知道是什么。我已经尝试使用 Apple 演示中的原始 .dae 模型，并转换为 .scn 文件。我已经在 .scnassets 文件夹的内部和外部尝试过它（以防它与 scnassets 向上轴的自动更正有关）。我尝试反转车轮转向轴，但这只会导致车轮在空中指向上方。
这是我的车辆创建函数，我尝试过的所有内容都被注释掉了。完整的回购协议在这里：https://github.com/Utsira/SCNPhysicsVehicle-test。谁能看到这里出了什么问题？提前致谢。
func setupCar() -> SCNNode {
let carScene = SCNScene(named: "art.scnassets/rc_car.scn") //rc_car.dae
let chassisNode = carScene!.rootNode.childNodeWithName("rccarBody", recursively: true)!
chassisNode.position = SCNVector3Make(0, 10, 30)
//chassisNode.rotation = SCNVector4(0, 1, 0, CGFloat(M_PI))
let body = SCNPhysicsBody.dynamicBody()
body.allowsResting = false
body.mass = 80
body.restitution = 0.1
body.friction = 0.5
body.rollingFriction = 0
chassisNode.physicsBody = body
scnScene.rootNode.addChildNode(chassisNode)
//getNode("rccarBody", fromDaePath: "rc_car.dae")
let wheelnode0 = chassisNode
.childNodeWithName("wheelLocator_FL", recursively: true)!
let wheelnode1 = chassisNode
.childNodeWithName("wheelLocator_FR", recursively: true)!
let wheelnode2 = chassisNode
.childNodeWithName("wheelLocator_RL", recursively: true)!
let wheelnode3 = chassisNode
.childNodeWithName("wheelLocator_RR", recursively: true)!
//wheelnode0.geometry!.firstMaterial!.emission.contents = UIColor.blueColor()
// SCNTransaction.begin()
// wheelnode0.rotation = SCNVector4(x: 0, y: 1, z: 0, w: Float(M_PI)) //CGFloat(M_PI)
// wheelnode1.rotation = SCNVector4(x: 0, y: 1, z: 0, w: Float(M_PI))
// wheelnode2.rotation = SCNVector4(x: 0, y: 1, z: 0, w: Float(M_PI))
// wheelnode3.rotation = SCNVector4(x: 0, y: 1, z: 0, w: Float(M_PI))
// SCNTransaction.commit()
// wheelnode0.eulerAngles = SCNVector3Make(0, Float(M_PI), 0 )
let wheel0 = SCNPhysicsVehicleWheel(node: wheelnode0)
let wheel1 = SCNPhysicsVehicleWheel(node: wheelnode1)
let wheel2 = SCNPhysicsVehicleWheel(node: wheelnode2)
let wheel3 = SCNPhysicsVehicleWheel(node: wheelnode3)
// wheel0.steeringAxis = SCNVector3Make(0, -1, 1) //wheels point up in the air with 0,1,0
// wheel1.steeringAxis = SCNVector3Make(0, -1, 1)
// wheel2.steeringAxis = SCNVector3Make(0, -1, 1)
// wheel3.steeringAxis = SCNVector3Make(0, -1, 1)
//
// wheel0.axle = SCNVector3(x: 1,y: 0,z: 0) //wheels face and spin the right way, but car moves in opposite direction with 1,0,0
// wheel1.axle = SCNVector3(x: 1,y: 0,z: 0)
// wheel2.axle = SCNVector3(x: 1,y: 0,z: 0)
// wheel3.axle = SCNVector3(x: 1,y: 0,z: 0)
// wheel0.steeringAxis = SCNVector3()
// var min = SCNVector3(x: 0, y: 0, z: 0)
// var max = SCNVector3(x: 0, y: 0, z: 0)
// wheelnode0.getBoundingBoxMin(&min, max: &max)
// let wheelHalfWidth = Float(0.5 * (max.x - min.x))
// var w0 = wheelnode0.convertPosition(SCNVector3Zero, toNode: chassisNode)
// w0 = w0 + SCNVector3Make(wheelHalfWidth, 0, 0)
// wheel0.connectionPosition = w0
// var w1 = wheelnode1.convertPosition(SCNVector3Zero, toNode: chassisNode)
// w1 = w1 - SCNVector3Make(wheelHalfWidth, 0, 0)
// wheel1.connectionPosition = w1
// var w2 = wheelnode2.convertPosition(SCNVector3Zero, toNode: chassisNode)
// w2 = w2 + SCNVector3Make(wheelHalfWidth, 0, 0)
// wheel2.connectionPosition = w2
// var w3 = wheelnode3.convertPosition(SCNVector3Zero, toNode: chassisNode)
// w3 = w3 - SCNVector3Make(wheelHalfWidth, 0, 0)
// wheel3.connectionPosition = w3
vehicle = SCNPhysicsVehicle(chassisBody: chassisNode.physicsBody!,
wheels: [wheel0, wheel1, wheel2, wheel3])
scnScene.physicsWorld.addBehavior(vehicle)
return chassisNode
}
我找到了解决方案：
（但不是我希望的解决方案）
我的解决方法是将“FrontLeftWheel”的连接位置调整到最右边，以致于它充当了“FrontRightWheel”的角色。
而“FrontRightWheel”，靠左太多，以至于它扮演了“FrontLeftWheel”的角色。
我也为背部做了这个。
基本上，你有：
SCNVector3Make(wheelHalfWidth, 0, 0)
我将其替换为：
SCNVector3Make(wheelHalfWidth * 5.2, 0, 0)
但是，您可能不得不使用数字“5.2”来匹配您的 COLLADA (.dae)。
注：
别忘了替换：
vehicle = SCNPhysicsVehicle(chassisBody: chassisNode.physicsBody!,
wheels: [wheel0, wheel1, wheel2, wheel3])
有：
vehicle = SCNPhysicsVehicle(chassisBody: chassisNode.physicsBody!,
wheels: [wheel1, wheel0, wheel3, wheel2])
这样，当你使用 car.wheels[0].
你就得到了你期望的轮子
我认为你的问题是你没有为每个轮子设置连接位置。 Apple 的默认 ObjectiveC 代码很难转换为 swift.
wheel0.connectionPosition = SCNVector3FromFloat3(SCNVector3ToFloat3([wheel0Node convertPosition:SCNVector3Zero toNode:chassisNode]) + (vector_float3){wheelHalfWidth, 0.0, 0.0});
wheel1.connectionPosition = SCNVector3FromFloat3(SCNVector3ToFloat3([wheel1Node convertPosition:SCNVector3Zero toNode:chassisNode]) - (vector_float3){wheelHalfWidth, 0.0, 0.0});
wheel2.connectionPosition = SCNVector3FromFloat3(SCNVector3ToFloat3([wheel2Node convertPosition:SCNVector3Zero toNode:chassisNode]) + (vector_float3){wheelHalfWidth, 0.0, 0.0});
wheel3.connectionPosition = SCNVector3FromFloat3(SCNVector3ToFloat3([wheel3Node convertPosition:SCNVector3Zero toNode:chassisNode]) - (vector_float3){wheelHalfWidth, 0.0, 0.0});
翻译这四行（忽略重复）
let wheel0Position = wheel0Node.convertPosition(SCNVector3Zero, to: chassisNode)
let vector0Float3 = vector_float3(wheel0Position.x, wheel0Position.y, wheel0Position.z) + vector_float3(wheelHalfWidth, 0,0)
wheel0.connectionPosition = SCNVector3(vector0Float3.x, vector0Float3.y, vector0Float3.z)
let wheel1Position = wheel1Node.convertPosition(SCNVector3Zero, to: chassisNode)
let vector1Float3 = vector_float3(wheel1Position.x, wheel1Position.y, wheel1Position.z) - vector_float3(wheelHalfWidth, 0,0)
wheel1.connectionPosition = SCNVector3(vector1Float3.x, vector1Float3.y, vector1Float3.z)
let wheel2Position = wheel2Node.convertPosition(SCNVector3Zero, to: chassisNode)
let vector2Float3 = vector_float3(wheel2Position.x, wheel2Position.y, wheel2Position.z) + vector_float3(wheelHalfWidth, 0,0)
wheel2.connectionPosition = SCNVector3(vector2Float3.x, vector2Float3.y, vector2Float3.z)
let wheel3Position = wheel3Node.convertPosition(SCNVector3Zero, to: chassisNode)
let vector3Float3 = vector_float3(wheel3Position.x, wheel3Position.y, wheel3Position.z) - vector_float3(wheelHalfWidth, 0,0)
wheel3.connectionPosition = SCNVector3(vector3Float3.x, vector3Float3.y, vector3Float3.z)
通过添加或减去 vector_float3，轮子定位在正确的位置。
此外，请记住您不能在场景中缩放节点，否则可能会发生奇怪的事情。
遇到同样的问题，我的解决办法是旋转所有轮子节点，使Y轴指向下方。我认为重力是向下的力。