如何检测何时在AR.js中找到标记 [英] How to detect when a marker is found in AR.js

问题描述

我正在尝试使用a框架在ar.js中发现/丢失标记的时候。

I'm trying to detect when a marker if found/lost in ar.js, while using a-frame.

根据我在源代码 ，应该触发 getMarker事件，而且artoolkit似乎调度了一个markerFound事件。

From what I see in the source code, when the marker is found, a 'getMarker' event should be fired, moreover artoolkit seems to dispatch a markerFound event.

我试图在上监听这些事件; a-scene> ，或在< a-marker> 上，但似乎我错了，或者我需要获取深入到 arController 或 arToolkit 对象。

I tried to listen to those events on the <a-scene>, or on the <a-marker>, but it seems I'm either mistaken, or i need to get deeper to the arController, or arToolkit objects.

当我记录场景或标记时，我仅获得对属性的引用，这些属性似乎没有附加上述对象。（例如 marker.arController 或 marker.getAttribute（'artoolkitmarker'）。arController ）

When i log the scene, or the marker, i only get references to the attributes, which don't seem to have the above objects attached.(like marker.arController, or marker.getAttribute('artoolkitmarker').arController)

是否有人尝试过此操作，并且有任何提示如何执行此操作？

Did anybody tried this and have any tips how to do this ?

推荐答案

PR303 会在发现和丢失标记时引入事件

PR303 introduces events when a marker is found and lost

• markerFound


• markerLost

• markerFound
• markerLost

只需添加事件侦听器即可使用它们：

You can use them by simply adding an event listener:

anchorRef.addEventListener("markerFound", (e)=>{ // your code here}

具有以下简单设置：

<a-marker id="anchor">
  <a-entity>
</a-marker>

示例此处。
请注意，自9月18日起，您需要使用 dev 分支来使用以上内容。

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原始答案-如果要手动执行

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通过检查是否可以找到标记该标记在需要时可见（其他事件或刻度）： if（document.querySelector（ a-marker）。object3D.visible == true）

example here. Please note, that as of sep 18', you need to use the dev branch to use the above.

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ORIGINAL ANWSER - in case you want to do it manually

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Detecting if the marker is found is possible by checking if the marker is visible when needed (other event, or on tick): if(document.querySelector("a-marker").object3D.visible == true)

例如：

init: function() {
   this.marker = document.querySelector("a-marker")
   this.markerVisible = false
},
tick: function() {
   if (!this.marker) return
   if (this.marker.object3D.visible) {
      if (!this.markerVisible) {
         // marker detected
         this.markerVisible = true
      }
   } else {
      if (this.markerVisbile) {
         // lost sight of the marker
         this.markerVisible = false
      }
   }
}

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正如adrian li指出的那样，它不适用于 a标记相机，仅用于 a-ma rkers

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