检查ARReferenceImage是否在相机视图中不再可见 [英] Check whether the ARReferenceImage is no longer visible in the camera's view

问题描述

我想检查 ARReferenceImage 在相机视图中是否不再可见.目前，我可以检查图像的节点是否在相机的视图中，但是当 ARReferenceImage 被其他图像覆盖或在移除图像时覆盖.

I would like to check whether the ARReferenceImage is no longer visible in the camera's view. At the moment I can check if the image's node is in the camera's view, but this node is still visible in the camera's view when the ARReferenceImage is covered with another image or when the image is removed.

func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) {
    guard let node = self.currentImageNode else { return }

    if let pointOfView = sceneView.pointOfView {
        let isVisible = sceneView.isNode(node, insideFrustumOf: pointOfView)
        print("Is node visible: \(isVisible)")
    }
}

因此，我需要检查图像是否不再可见，而不是图像的节点可见性.但是我无法确定这是否可行.第一个屏幕截图显示了找到下面的图像时添加的三个框.当找到的图像被覆盖时(请参见屏幕截图2)，我想删除这些框.

So I need to check if the image is no longer visible instead of the image's node visibility. But I can't find out if this is possible. The first screenshot shows three boxes that are added when the image beneath is found. When the found image is covered (see screenshot 2) I would like to remove the boxes.

推荐答案

我设法解决了该问题！使用Maybe1的一些代码和他的概念来解决问题，但是方式不同.以下代码行仍用于重新激活图像识别.

I managed to fix the problem! Used a little bit of Maybe1's code and his concept to solving the problem, but in a different way. The following line of code is still used to reactivate the image recognition.

// Delete anchor from the session to reactivate the image recognition
sceneView.session.remove(anchor: anchor) 

让我解释一下.首先，我们需要添加一些变量.

Let me explain. First we need to add some variables.

// The scnNodeBarn variable will be the node to be added when the barn image is found. Add another scnNode when you have another image.    
var scnNodeBarn: SCNNode = SCNNode()
// This variable holds the currently added scnNode (in this case scnNodeBarn when the barn image is found)     
var currentNode: SCNNode? = nil
// This variable holds the UUID of the found Image Anchor that is used to add a scnNode    
var currentARImageAnchorIdentifier: UUID?
// This variable is used to call a function when there is no new anchor added for 0.6 seconds    
var timer: Timer!

带有下面注释的完整代码.

The complete code with comments below.

/// - Tag: ARImageAnchor-Visualizing
func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) {
    guard let imageAnchor = anchor as? ARImageAnchor else { return }

    let referenceImage = imageAnchor.referenceImage

    // The following timer fires after 0.6 seconds, but everytime when there found an anchor the timer is stopped.
    // So when there is no ARImageAnchor found the timer will be completed and the current scene node will be deleted and the variable will set to nil
    DispatchQueue.main.async {
        if(self.timer != nil){
            self.timer.invalidate()
        }
        self.timer = Timer.scheduledTimer(timeInterval: 0.6 , target: self, selector: #selector(self.imageLost(_:)), userInfo: nil, repeats: false)
    }

    // Check if there is found a new image on the basis of the ARImageAnchorIdentifier, when found delete the current scene node and set the variable to nil
    if(self.currentARImageAnchorIdentifier != imageAnchor.identifier &&
        self.currentARImageAnchorIdentifier != nil
        && self.currentNode != nil){
            //found new image
            self.currentNode!.removeFromParentNode()
            self.currentNode = nil
    }

    updateQueue.async {

        //If currentNode is nil, there is currently no scene node
        if(self.currentNode == nil){

            switch referenceImage.name {
                case "barn":
                    self.scnNodeBarn.transform = node.transform
                    self.sceneView.scene.rootNode.addChildNode(self.scnNodeBarn)
                    self.currentNode = self.scnNodeBarn
                default: break
            }

        }

        self.currentARImageAnchorIdentifier = imageAnchor.identifier

        // Delete anchor from the session to reactivate the image recognition
        self.sceneView.session.remove(anchor: anchor)
    }

}

在计时器结束时删除节点，表明未找到新的ARImageAnchor.

Delete the node when the timer is finished indicating that there was no new ARImageAnchor found.

@objc
    func imageLost(_ sender:Timer){
        self.currentNode!.removeFromParentNode()
        self.currentNode = nil
    }

这样，当覆盖图像或找到新图像时，将删除当前添加的scnNode.

In this way the currently added scnNode wil be deleted when the image is covered or when there is found a new image.

不幸的是，由于以下原因，该解决方案不能解决图像的定位问题:

This solution does unfortunately not solve the positioning problem of images because of the following:

ARKit不会跟踪每个检测到的图像的位置或方向的变化.

ARKit doesn’t track changes to the position or orientation of each detected image.

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