Swift Scenekit相机：在角色方向

Question

我正在尝试使用Swift创建自己的游戏，我想知道如何在SceneKit中使用相机将其固定在角色头部的背面，并随着相机移动和旋转。

我的第一个想法是让角色的方向等于相机的方向，但这不起作用。

我的第二个想法是使用一些相机限制，但它们似乎都不起作用。我使用了lookAtConstraint，replicatorConstraint和distanceConstraint的组合。我当时认为使用IKConstraint可能会有效，但是当我使用它时总会给我一个错误。

如果有人有任何建议会得到很好的理解，我对于使用的内容有点用尽了。谢谢!!

以下是设置相机的功能：

func setupFollowCamera(_ cameraNode: SCNNode) {
    // look at "lookAtTarget"
    let lookAtConstraint = SCNLookAtConstraint(target: self.lookAtTarget)
    lookAtConstraint.influenceFactor = 0.07
    lookAtConstraint.isGimbalLockEnabled = true

    // distance constraints
    let follow = SCNDistanceConstraint(target: self.lookAtTarget)
    let distance = CGFloat(simd_length(cameraNode.simdPosition))
    follow.minimumDistance = distance
    follow.maximumDistance = distance

    // configure a constraint to maintain a constant altitude relative to the character
    let desiredAltitude = abs(cameraNode.simdWorldPosition.y)
    weak var weakSelf = self

    let keepAltitude = SCNTransformConstraint.positionConstraint(inWorldSpace: true, with: {(_ node: SCNNode, _ position: SCNVector3) -> SCNVector3 in
        guard let strongSelf = weakSelf else { return position }
        var position = float3(position)
        position.y = strongSelf.character!.baseAltitude + Float(0.75)
        return SCNVector3( position )
    })

    // replicator constraint
    let repli = SCNReplicatorConstraint(target: self.lookAtTarget)
    repli.positionOffset = SCNVector3(0, 0, 1)
    repli.replicatesOrientation = true

    //let ik = SCNIKConstraint(chainRootNode: (self.character?.node)!)


    // use a custom constraint to let the user orbit the camera around the character
    let transformNode = SCNNode()
    let orientationUpdateConstraint = SCNTransformConstraint(inWorldSpace: true) { (_ node: SCNNode, _ transform: SCNMatrix4) -> SCNMatrix4 in
        guard let strongSelf = weakSelf else { return transform }
        if strongSelf.activeCamera != node {
            return transform
        }



        let targetPosition = strongSelf.lookAtTarget.presentation.simdWorldPosition
        let cameraDirection = strongSelf.cameraDirection
        //let cameraDirection = strongSelf.characterDirection
        if cameraDirection.allZero() {
            return transform
        }


        let characterWorldUp = strongSelf.character?.node?.presentation.simdWorldUp

        transformNode.transform = transform

        let q = simd_mul(
            simd_quaternion(GameController.CameraOrientationSensitivity * cameraDirection.x, characterWorldUp!),
            simd_quaternion(GameController.CameraOrientationSensitivity * cameraDirection.y, transformNode.simdWorldRight)
        )

        transformNode.simdRotate(by: q, aroundTarget: targetPosition)
        return transformNode.transform
    }

    //cameraNode.constraints = [keepAltitude, orientationUpdateConstraint, lookAtConstraint, follow]
    cameraNode.constraints = [lookAtConstraint, repli]
}