如何在 swift 中沿着车轮移动车身？

Question

我一直在尝试移动车身和车轮。我创建了增强现实项目，其中将汽车模型放置在水平面上，汽车由四个按钮控制，即加速、转向、倒车和刹车。车左、右在加速和倒车的时候都是通过转向控制的。

实际上我现在可以将 3d 汽车模型放置在水平面上，但不知道如何随着车身向前和向后旋转车轮。

这是我一直在尝试放置 3d 对象的代码：

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

    if let touch = touches.first {

        // gives us the location of where we touched on the 2D screen.
        let touchLocation = touch.location(in: sceneView)

        // hitTest is performed to get the 3D coordinates corresponding to the 2D coordinates that we got from touching the screen.
        // That 3d coordinate will only be considered when it is on the existing plane that we detected.
        let results = sceneView.hitTest(touchLocation, types: .existingPlaneUsingExtent)

        // if we have got some results using the hitTest then do this.
        if let hitResult = results.first {


           let boxScene = SCNScene(named: "art.scnassets/porsche.scn")!

            if let boxNode = boxScene.rootNode.childNode(withName: "car", recursively: true) {
                print("box:::\(boxNode.childNodes)")

                boxNode.position = SCNVector3(x: hitResult.worldTransform.columns.3.x, y: hitResult.worldTransform.columns.3.y + 0.15, z: hitResult.worldTransform.columns.3.z)

                // finally the box is added to the scene.
                sceneView.scene.rootNode.addChildNode(boxNode)

            }


        }

    }
}

检测水平面功能代码：

   func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) {

    if anchor is ARPlaneAnchor {

        // anchors can be of many types, as we are just dealing with horizontal plane detection we need to downcast anchor to ARPlaneAnchor
        let planeAnchor = anchor as! ARPlaneAnchor

        // creating a plane geometry with the help of dimentions we got using plane anchor.
        let plane = SCNPlane(width: CGFloat(planeAnchor.extent.x), height: CGFloat(planeAnchor.extent.z))

        // a node is basically a position.
        let planeNode = SCNNode()

        // setting the position of the plane geometry to the position we got using plane anchor.
        planeNode.position = SCNVector3(x: planeAnchor.center.x, y: 0, z: planeAnchor.center.z)

        // when a plane is created its created in xy plane instead of xz plane, so we need to rotate it along x axis.
        planeNode.transform = SCNMatrix4MakeRotation(-Float.pi/2, 1, 0, 0)

        //create a material object
        let gridMaterial = SCNMaterial()

        //setting the material as an image. A material can also be set to a color.
        gridMaterial.diffuse.contents = UIImage(named: "art.scnassets/grid.png")

        // assigning the material to the plane
        plane.materials = [gridMaterial]


        // assigning the position to the plane
        planeNode.geometry = plane

        //adding the plane node in our scene
        node.addChildNode(planeNode)



    }

    else {

        return
    }

}

非常感谢任何帮助！！！

Answer 1

这是一项相当全面的任务。

你应该把你的车做成 SCNPhysicsVehicle 的子类。

SCNPhysicsVehicle 是一种物理行为，它修改物理体使其表现得像汽车、摩托车或其他轮式车辆。

要构建车辆，请指定一个 SCNPhysicsBody 对象作为其底盘，并指定一组 SCNPhysicsVehicleWheel 对象作为其车轮。对于每个轮子，您定义物理特性，例如悬架和牵引力，并在场景中关联一个节点以提供轮子的大小和视觉表示。构建车辆后，您可以控制它的加速、制动和转向。

一般：https://developer.apple.com/documentation/scenekit/scnphysicsbody

车轮：https://developer.apple.com/documentation/scenekit/scnphysicsvehiclewheel

示例：

var vehicle = SCNPhysicsVehicle()

你需要用静态体创建地面。

func createGround(planeAnchor: ARPlaneAnchor) -> SCNNode {
   let ground = SCNNode(geometry: SCNPlane(width: CGFloat(planeAnchor.extent.x), height: CGFloat(CGFloat(planeAnchor.extent.z))))
   ground.position = SCNVector3(planeAnchor.center.x,planeAnchor.center.y,planeAnchor.center.z)
   ground.eulerAngles = SCNVector3(90.degreesToRadians, 0, 0)
   let staticBody = SCNPhysicsBody.static() // it must be static
   ground.physicsBody = staticBody
   return ground
   }

您需要设置您的汽车。

func setupCar() {

let scene = SCNScene(named: "YourScene.scn")
let chassis = (scene?.rootNode.childNode(withName: "chassis", recursively: true))! // Your chassis
let frontLeftWheel = chassis.childNode(withName: "frontLeftWheel", recursively: true)!
let frontRightWheel = chassis.childNode(withName: "frontRightWheel", recursively: true)!
let rearLeftWheel = chassis.childNode(withName: "rearLeftWheel", recursively: true)!
let rearRightWheel = chassis.childNode(withName: "rearRightWheel", recursively: true)!

// physic behavior for wheels

let v_frontLeftWheel = SCNPhysicsVehicleWheel(node: frontLeftWheel)
let v_frontRightWheel = SCNPhysicsVehicleWheel(node: frontRightWheel)
let v_rearRightWheel = SCNPhysicsVehicleWheel(node: rearLeftWheel)
let v_rearLeftWheel = SCNPhysicsVehicleWheel(node: rearRightWheel)


chassis.position = SCNVector(0,0,0) // insert your desired position
let body = SCNPhysicsBody(type: .dynamic, shape: SCNPhysicsShape(node: chassis, options: [SCNPhysicsShape.Option.keepAsCompound: true]))
body.mass = 1
chassis.physicsBody = body
self.vehicle = SCNPhysicsVehicle(chassisBody: chassis.physicsBody!, wheels: [v_rearRightWheel, v_rearLeftWheel, v_frontRightWheel, v_frontLeftWheel])
self.sceneView.scene.physicsWorld.addBehavior(self.vehicle)
self.sceneView.scene.rootNode.addChildNode(chassis)
}

现在你可以操纵你的车了。

 func renderer(_ renderer: SCNSceneRenderer, didSimulatePhysicsAtTime time: TimeInterval) {

 var engineForce: CGFloat = 5
 var brakingForce: CGFloat = 0

 // here you can manipulate your car steering angle
 self.vehicle.setSteeringAngle(0, forWheelAt: 2) 
 self.vehicle.setSteeringAngle(0, forWheelAt: 3)


 self.vehicle.applyEngineForce(engineForce, forWheelAt: 0)
 self.vehicle.applyEngineForce(engineForce, forWheelAt: 1)
 self.vehicle.applyBrakingForce(0, forWheelAt: 0)
 self.vehicle.applyBrakingForce(0, forWheelAt: 1)
 }

P.S。不要忘记添加到您的 viewDidLoad():

        self.sceneView.delegate = self
        self.sceneView.scene?.physicsWorld.contactDelegate = self

P.P.S 这只是一般的想法，您必须做一些研究并找到适合您的具体情况的工作解决方案。

给你一个小提示，转向可以通过 CoreMotion 完成。

希望对您有所帮助！

如何在 swift 中沿着车轮移动车身？

How to move car body along wheels in swift?

ios

swift

arkit