swift - 旋转 SCNNode 然后相对于旋转移动？

Question

我的节点设置:

let node = SCNNode()
node.position = SCNVector3(0.0, 0.0, 0.0)

然后我希望将节点向左旋转 90 度，这可以通过以下方式实现:

node.transform = SCNMatrix4Rotate(node.transform, .pi/2, 0.0, 1.0, 0.0)

接下来，我想将节点相对于当前旋转沿负 z 轴向前平移一个单位，并以:

node.position = SCNVector3(-1.0, 0.0, 0.0)

我不知道如何以编程方式从节点的旋转到节点的位置。

Basically node begins at (0, 0, 0), its forward vector is the -z axis, node turns left and moves one unit forward to end up at (-1, 0, 0).

这不起作用:

func move(_ direction: moveDirection) {
    switch direction {
    case .forward: characterNode.position = SCNVector3(characterNode.position.x, characterNode.position.y, characterNode.position.z - 1.0)
    case .left: characterNode.pivot = SCNMatrix4Rotate(characterNode.pivot, -.pi/32, 0.0, 1.0, 0.0)
    case .backward: characterNode.position = SCNVector3(characterNode.position.x, characterNode.position.y, characterNode.position.z + 1.0)
    case .right: characterNode.pivot = SCNMatrix4Rotate(characterNode.pivot, .pi/32, 0.0, 1.0, 0.0)
    }
}

Answer 1

假设我没有理解错，一旦你旋转了你的 SCNNode，你想要将它朝那个方向向前移动。

这可以通过使用 worldFront 值来完成，它很简单:

The local unit -Z axis (0,0,-1) in world space.

因此这可能是您正在寻找的答案:

    //1. Create A Node Holder
    let nodeToAdd = SCNNode()

    //2. Create An SCNBox Geometry
    let nodeGeometry = SCNBox(width: 0.2, height: 0.2, length: 0.2, chamferRadius: 0)
    nodeGeometry.firstMaterial?.diffuse.contents = UIColor.cyan
    nodeGeometry.firstMaterial?.lightingModel = .constant
    nodeToAdd.geometry = nodeGeometry

    //3. Position It 1.5m Away From The Camera
    nodeToAdd.position = SCNVector3(0, 0, -1.5)

    //4. Rotate The Node By 90 Degrees On It's Y Axis
    nodeToAdd.rotation = SCNVector4Make(0, 1, 0, .pi / 2)

    //5. Add The Node To The ARSCNView
    augmentedRealityView.scene.rootNode.addChildNode(nodeToAdd)

    //6. Use The World Front To Move The Node Forward e.g 

    /*
    nodeToAdd.simdPosition += nodeToAdd.simdWorldFront * 1.2
    */

    nodeToAdd.simdPosition += nodeToAdd.simdWorldFront

    //7. Print The Position
    print(nodeToAdd.position)

     /*
    SCNVector3(x: -0.999999881, y: 0.0, z: -1.50000024)
    */