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

我正在尝试检测标记是否在 ar.js 中找到/丢失，同时使用 a-frame.

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

从我在 源中看到的代码，当找到标记时，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 或 上收听这些事件，但似乎我要么错了，或者我需要更深入地了解 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，我只获得对属性的引用，这些属性似乎没有附加上述对象.(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)

有没有人试过这个并有任何提示如何做到这一点?

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

推荐答案

PR303 在标记被发现和丢失时引入事件

PR303 introduces events when a marker is found and lost

• markerFound
• markerLost

您只需添加一个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}

简单的设置如下:

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

示例 此处.请注意，从 9 月 18 日开始，您需要使用 dev 分支才能使用上述内容.<小时>原始ANWSER - 如果您想手动进行

---

通过检查标记在需要时是否可见(其他事件或勾选时)可以检测是否找到标记: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.

---

ORIGINAL ANWSER - in case you want to do it manually

---

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
      }
   }
}

<小时>正如阿德里安李指出的那样，它不适用于 a-marker-camera，仅适用于 a-markers

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