Question

嘿，我有一个被施力施加的球。我试图让它做的事情基本上是在它通过空气到达目的地时重力作用于它的因果效应。基本上当＆＃34;移动到＆＃34;动作正在发挥重力并没有受到影响所以不是慢慢地倒在地上而是移动到它的最终位置然后当它移动到＆＃34;行动停止。做到场景中的引力。

我试图将球抛向弧线并降落在目标身上？

代码：

                   func CreateBall() {
    let BallScene = SCNScene(named: "art.scnassets/Footballs.dae")
    Ball = BallScene!.rootNode.childNodeWithName("Armature", recursively: true)! //the Amature/Bones
    Ballbody = BallScene!.rootNode.childNodeWithName("Ball", recursively: true)!

    let collisionCapsuleRadius3 = CGFloat(0.01) // Width of physicsBody
    let collisionCapsuleHeight3 = CGFloat(0.01) // Height of physicsBody
    Ball.position = SCNVector3Make(Guy.position.x, Guy.position.y, Guy.position.z)
    Ball.scale = SCNVector3Make(5, 5, 5)
    Ball.rotation = SCNVector4Make(0.0,0.0,0.0,0.0) // x,y,z,w

    Ball.physicsBody = SCNPhysicsBody(type: .Dynamic, shape:SCNPhysicsShape(geometry: SCNCapsule(capRadius: collisionCapsuleRadius3, height: collisionCapsuleHeight3), options:nil))
    Ball.physicsBody?.affectedByGravity = true
    Ball.physicsBody?.friction = 1 //
    Ball.physicsBody?.restitution = 0 //bounceness of the object. 1.0 will boounce forever
    Ball.physicsBody?.angularDamping = 1 // ability to rotate
    Ball.physicsBody?.mass = 1
    Ball.physicsBody?.rollingFriction = 1
    Ball.physicsBody!.categoryBitMask = BitmaskCollision4
    Ball.physicsBody?.contactTestBitMask = BitmaskCollision3 //| BitmaskCollision2
    Ballbody.physicsBody?.collisionBitMask = BitmaskCollision2 | BitmaskCollision3 | BitmaskCollision//| BitmaskCollision2

    scnView.scene!.rootNode.addChildNode(Ball)
    scnView.scene!.rootNode.addChildNode(Ballbody)


    }
    CreateBall()

现在这就是魔术发生的地方：

                   scnView.scene!.physicsWorld.gravity = SCNVector3(x: 0, y: -9.8, z: 0)

                    let location = SCNVector3(Guy2.presentationNode.position.x, 0.0, Guy2.presentationNode.position.z + Float(50) )
                    let moveAction = SCNAction.moveTo(location, duration: 2.0)
                    Ball.runAction(SCNAction.sequence([moveAction]))


                    let forceApplyed = SCNVector3(x: 0.0, y: 100.0 , z: 0.0)
                     Ball.physicsBody?.applyForce(forceApplyed, atPosition: Ball.presentationNode.position, impulse: true)

Answer 1

组合SCNActions和物理不起作用，您需要使用其中一个。使用物理，您可以计算推动节点到达目标所需的精确力。

我为Unity found here调整了一个解决方案并使用了SCNVector3 extension，这使得一些计算变得更加容易。

基本上你传入了一个你要投掷的SCNNode，一个SCNVector3用于目标，一个angle（以弧度表示）你想要投掷该节点。然后，此功能将计算出达到目标所需的力。

func shootProjectile() {
    let velocity = ballisticVelocity(ball, target: target.position, angle: Float(0.4))
    ball.physicsBody?.applyForce(velocity, impulse: true)
}

func ballisticVelocity(projectile:SCNNode, target: SCNVector3, angle: Float) -> SCNVector3 {
        let origin = projectile.presentationNode.position
        var dir = target - origin       // get target direction
        let h = dir.y                   // get height difference
        dir.y = 0                       // retain only the horizontal direction
        var dist = dir.length()         // get horizontal distance
        dir.y = dist * tan(angle)       // set dir to the elevation angle
        dist += h / tan(angle)          // correct for small height differences
        // calculate the velocity magnitude
        let vel = sqrt(dist * -scene.physicsWorld.gravity.y / sin(2 * angle))
        return dir.normalized() * vel * Float(projectile.physicsBody!.mass)
}

将physicsBody的damping设置为0也很重要，否则会受到空气阻力的影响。

我不打算假装确切知道它是如何工作的，但维基百科有文章解释它背后的所有数学。

<强>更新

由于使用上面的代码，我注意到它并不总是有效，特别是当原点和目标的高度不同时。在同一个论坛上，这个功能似乎更可靠。

func calculateBestThrowSpeed(origin: SCNVector3, target: SCNVector3, timeToTarget:Float) -> SCNVector3 {

    let gravity:SCNVector3 = sceneView.scene!.physicsWorld.gravity

    let toTarget = target - origin
    var toTargetXZ = toTarget
    toTargetXZ.y = 0

    let y = toTarget.y
    let xz = toTargetXZ.length()

    let t = timeToTarget
    let v0y = y / t + 0.5 * gravity.length() * t
    let v0xz = xz / t


    var result = toTargetXZ.normalized()
    result *= v0xz
    result.y = v0y

    return result
}

如何申请SCNAction＆amp;对SCNNode的冲动力

1 个答案: