渲染回调时修改场景

Question

我有以下代码，出现了错误：

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

    if anchor is ARImageAnchor {  

        let phoneScene = SCNScene(named: "Phone_01.scn")!
        let phoneNode = phoneScene.rootNode.childNode(withName: "parentNode", recursively: true)!

        // rotate the phone node
        let rotationAction = SCNAction.rotateBy(x: 0, y: 0.5, z: 0, duration: 1)
        let inifiniteAction = SCNAction.repeatForever(rotationAction)
        phoneNode.runAction(inifiniteAction)          
        phoneNode.position = SCNVector3(anchor.transform.columns.3.x,anchor.transform.columns.3.y + 0.1,anchor.transform.columns.3.z)              
        node.addChildNode(phoneNode)
    }                 
}

在另一个场景的渲染回调中修改了场景。因此，我将其替换为以下内容：

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

    if anchor is ARImageAnchor {

        DispatchQueue.global().async {

            let phoneScene = SCNScene(named: "Phone_01.scn")!
            let phoneNode = phoneScene.rootNode.childNode(withName: "parentNode", recursively: true)!

            DispatchQueue.main.async {

                // rotate the phone node
                let rotationAction = SCNAction.rotateBy(x: 0, y: 0.5, z: 0, duration: 1)
                let inifiniteAction = SCNAction.repeatForever(rotationAction)
                phoneNode.runAction(inifiniteAction)
                phoneNode.position = SCNVector3(anchor.transform.columns.3.x,anchor.transform.columns.3.y + 0.1,anchor.transform.columns.3.z) 
                node.addChildNode(phoneNode)
            }  
        }
    }    
}

现在错误已经消失了，一切都正常工作。我的问题是：这是正确的解决方案吗？我应该切换到后台线程来加载场景，然后切换到主线程来添加节点吗？节点是否会添加在主线程上？

- john doe

---

这解决了问题吗？我尝试了一下，它确实从控制台中删除了消息。我的应用程序有时会崩溃，我认为是因为它，但我不确定这个解决方案是否能防止进一步的崩溃。 - Hols

各位好，你们找到解决问题的正确方法了吗？ - Sergey Didanov

Answer 1

在方法代理中尝试像这样的内容。这是一个旧项目的示例。

DispatchQueue.main.async {
        if let imageAnchor = anchor as? ARImageAnchor {

            let plane = SCNPlane(width: imageAnchor.referenceImage.physicalSize.width, height: imageAnchor.referenceImage.physicalSize.height)
            plane.firstMaterial?.diffuse.contents = UIColor(white: 1.0, alpha: 0.5)

            let planeNode = SCNNode(geometry: plane)
            planeNode.eulerAngles.x = -.pi
            node.addChildNode(planeNode)

            ...

        }
    }

- Diego Isco