swift - SCNNode 的 ARAnchor

Question

在将 SCNNode 添加到 ARSCNView 的场景后，我试图获取 anchor 。我的理解是应该自动创建 anchor ，但我似乎无法检索它。

下面是我添加它的方法。该节点保存在一个名为 testNode 的变量中。

let node = SCNNode()
node.geometry = SCNBox(width: 0.5, height: 0.1, length: 0.3, chamferRadius: 0)
node.geometry?.firstMaterial?.diffuse.contents = UIColor.green

sceneView.scene.rootNode.addChildNode(node)

testNode = node

这是我尝试检索它的方法。它总是打印 nil。

if let testNode = testNode {
    print(sceneView.anchor(for: testNode))
}

它不创建 anchor 吗？如果是这样:我可以使用另一种方法来检索它吗？

Answer 1

如果您查看 Apple Docs，它指出:

To track the positions and orientations of real or virtual objects relative to the camera, create anchor objects and use the add(anchor:) method to add them to your AR session.

因此，我认为由于您没有使用 PlaneDetection，如果需要，您需要手动创建一个 ARAnchor:

Whenever you place a virtual object, always add an ARAnchor representing its position and orientation to the ARSession. After moving a virtual object, remove the anchor at the old position and create a new anchor at the new position. Adding an anchor tells ARKit that a position is important, improving world tracking quality in that area and helping virtual objects appear to stay in place relative to real-world surfaces.

您可以在以下主题中阅读更多相关信息 What's the difference between using ARAnchor to insert a node and directly insert a node?

无论如何，为了让您开始，我首先创建了一个名为 currentNode 的 SCNNode:

var currentNode: SCNNode?

然后使用 UITapGestureRecognizer 我在 touchLocation 手动创建了一个 ARAnchor:

@objc func handleTap(_ gesture: UITapGestureRecognizer){

        //1. Get The Current Touch Location
        let currentTouchLocation = gesture.location(in: self.augmentedRealityView)

        //2. If We Have Hit A Feature Point Get The Result
        if let hitTest = augmentedRealityView.hitTest(currentTouchLocation, types: [.featurePoint]).last {

            //2. Create An Anchore At The World Transform
            let anchor = ARAnchor(transform: hitTest.worldTransform)

            //3. Add It To The Scene
            augmentedRealitySession.add(anchor: anchor)


        }

 }

添加 anchor 后，我使用 ARSCNViewDelegate 回调来创建 currentNode，如下所示:

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

        if currentNode == nil{
            currentNode = SCNNode()
            let nodeGeometry = SCNBox(width: 0.2, height: 0.2, length: 0.2, chamferRadius: 0)
            nodeGeometry.firstMaterial?.diffuse.contents = UIColor.cyan
            currentNode?.geometry = nodeGeometry
            currentNode?.position = SCNVector3(anchor.transform.columns.3.x, anchor.transform.columns.3.y, anchor.transform.columns.3.z)
            node.addChildNode(currentNode!)

        }
 }

为了测试它是否有效，例如能够记录相应的 ARAnchor，我更改了 tapGesture 方法以在末尾包含它:

if let anchorHitTest = augmentedRealityView.hitTest(currentTouchLocation, options: nil).first,{
            print(augmentedRealityView.anchor(for: anchorHitTest.node))
}

在我的 ConsoleLog 中打印:

Optional(<ARAnchor: 0x1c0535680 identifier="23CFF447-68E9-451D-A64D-17C972EB5F4B" transform=<translation=(-0.006610 -0.095542 -0.357221) rotation=(-0.00° 0.00° 0.00°)>>)

希望对你有帮助