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Handy makes defining and recognizing custom hand poses in WebXR a snap!

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👉 Handy.js 👈
========================================================================
Want to add hand pose recognition to your 
[WebXR](https://developer.mozilla.org/en-US/docs/Web/API/WebXR_Device_API) 
project? **Handy** makes defining and recognizing custom hand poses a 
snap! Why use hand-held controllers when you can use your bare hands? 👋
Built on [Three.js](https://threejs.org/) and tested on the 
[Oculus Quest](https://www.oculus.com/quest/), **Handy** recognizes 
over 100 hand poses right out of the box—including the 
[American Sign Language (ASL) alphabet](https://en.wikipedia.org/wiki/American_Sign_Language).

**_UPDATE_**. May 2021. While a recent overhaul of the 
[WebXR Hands API](https://immersive-web.github.io/webxr-hand-input/) 
had temporarily broken **Handy**, we are once again 100% functional 👍
Curious what happened? See 
[this issue](https://github.com/stewdio/handy.js/issues/4) 
for more details.

**Explore the demo**.
👉 Make your hand into a “finger gun” pose, then tap your thumb down 
onto your middle finger to shoot lasers from your hand. ✊ Make a fist
to cycle through different hand model visual styles. ✌️ Make a “peace 
sign” to toggle the hand-specific colors—red for right, green for left.
This demo is live at 
[https://stewartsmith.io/handy](https://stewartsmith.io/handy)
and the open-source code repository is available at
[https://github.com/stewdio/handy.js](https://github.com/stewdio/handy.js).  
  
**Pose vs. Gesture**. 
You may notice we use the term “hand pose” rather than “hand gesture”
and that’s because “gesture” implies movement over time and a spatial
relationship to the body or other objects. Right now **Handy** is 
primarily concerned with the basic pose of a hand’s configuration.
But it’s still early days—and yes, full hand gesture recognition is on 
the roadmap 👍

How to: Make it handy
------------------------------------------------------------------------
[Three.js](https://threejs.org/) already does the heavy lifting by
interacting with the [WebXR hand tracking 
API](https://immersive-web.github.io/webxr-hand-input/), creating a
[`THREE.Group`](https://threejs.org/docs/#api/en/objects/Group) per
each joint within a hand model, updating those joint positions /
rotations within its own update loop, and even creating multiple visual
models to use. (See Three’s [VR hand input profiles 
example](https://threejs.org/examples/#webxr_vr_handinput_profiles) and 
its [source 
code](https://github.com/mrdoob/three.js/blob/master/examples/webxr_vr_handinput_profiles.html)
for details.) But Three doesn’t include an easy way to define and listen
for hand poses.  Here’s how easy it is to “Handify” an 
existing Three.js hand input example:

```javascript

//  Use Three.js to hookup hand inputs:

hand0 = renderer.xr.getHand( 0 )
hand1 = renderer.xr.getHand( 1 )

//  Now use Handy to “Handify” them:

Handy.makeHandy( hand0 )
Handy.makeHandy( hand1 )

//  Which one is which?
// (We won’t know until the browser returns tracking data.)

handLeft = Handy.hands.getLeft()

````

Put this one command in your animation loop to update all handified 
objects.
```javascript

Handy.update()

```

And that’s it. You’re good to go 👍  
  
  
  
  
How to: Listen for hand poses
------------------------------------------------------------------------
**Handy** provides an `isPose` method on each hand which expects a
pose name as an argument. It returns `false` if the live hand data does
not most resemble that pose, or returns a search result object (which 
includes a reference to the pose definition data as well a `distance` 
property representing the 
[Euclidean distance](https://en.wikipedia.org/wiki/K-means_clustering))
if the live hand data does indeed most resemble the indicated pose.

```javascript

const isPeace = handLeft.isPose( 'peace' )
if( isPeace ){

//  Do something the entire time
	//  that our hand most resembles
	//  a “peace” pose.

//  For example, let’s log
	//  the Euclidean distance
	//  of that search result.

console.log( isPeace.distance )
}

```

An optional second argument, a
[Euclidean distance](https://en.wikipedia.org/wiki/K-means_clustering)
threshold, follows a similar pattern as above, but does not require
that the pose be the top search result. Instead the pose must be
closer than the supplied distance threshold.

```javascript

if( handLeft.isPose( 'peace', 3000 )){

//  Do something the entire time
	//  that our hand resembles
	//  a “peace” pose
	//  within a Euclidean distance of
	//  less than or equal to 3,000 millimeters.
}

````
  
  
**Handy** also fires events on the handified object itself to inform you
the moment a pose appears or vanishes.

```javascript

handLeft.addEventListener(

'peace pose began', 
	 function( event ){

//  Do something when the
		// “peace” pose appears.
	}
)
handLeft.addEventListener(

'peace pose ended',
	 function( event ){

//  Do something when the
		// “peace” pose vanishes.
	}
)

```  
The content of the passed `event` argument is:

```javascript

{
	type,    //  Event name, eg. “peace pose began”.
	hand,    //  Hand object itself.
	pose,    //  Pose definition data.
	distance,//  Euclidean distance between live hand pose and this pose.
	message  //  A human-readable description of the event, 
	         //  eg. “LEFT hand peace pose began”.
}

```
  
  
  
  
How to: Record your own hand poses
------------------------------------------------------------------------
1. First, you will need to enable remote debugging for your Oculus Quest.
See [Oculus’ guide to enabling remote 
debugging](https://developer.oculus.com/documentation/oculus-browser/browser-remote-debugging/?device=QUEST).
 
2. To make **Handy** accessible from your [JavaScript 
console](https://developers.google.com/web/tools/chrome-devtools/console/javascript)
you must create a globally accessible reference to it in your code. For 
example, this demo declares `window.Handy = Handy`.

3. Now from your [JavaScript 
console](https://developers.google.com/web/tools/chrome-devtools/console/javascript)
you can record a new pose with something similar to the following:
`Handy.hands.getLeft().recordLivePose( 'my pose name' )`. This will 
output a pose definition as a [JSON 
string](https://en.wikipedia.org/wiki/JSON) to your console that you 
can then paste into your pose definitions file. For this demo the 
appropriate location would be `./scripts/Handy-poses-left.js`.
This command will _also_ add the pose into that hand’s pose library 
immediately—so your code can make use of that new hand pose in the 
very next `hand.search()` call.  
  
**Example**
```javascript

//  Pose your left hand into the Vulcan
// “Live long and prosper” salute,
//  then hit enter on the following in your console:

Handy.hands.getLeft().recordLivePose( 'vulcan' )

//  Handy will return a snapshot of the pose.
//  Note that the position measurements are in millimeters
//  relative to the wrist joint position.

{"names":["vulcan"],"handedness":"left","handyRevision":4,"time":1598280104572,"headPosition":[-1156,5370,-2368],"headRotation":[-3.700743415417188e-17,0,0,1],"jointPositions":[[0,0,0],[32,10,-32],[51,14,-58],[77,18,-79],[90,18,-100],[41,9,-16],[96,7,-24],[132,20,-24],[154,29,-24],[176,34,-22],[41,9,-3],[96,3,-2],[134,21,-5],[159,33,-6],[183,39,-7],[38,9,8],[89,7,17],[123,23,27],[146,35,33],[168,43,39],[34,9,23],[78,14,35],[107,16,44],[123,29,46],[141,40,47]],"digitTipPositions":[[90,18,-100],[176,34,-22],[183,39,-7],[168,43,39],[141,40,47]]},

````
  
Note that the `names` property of a pose definition is an Array. One 
pose can have many names. Multiple poses can share the same name. 
**Handy** is quite flexible and will automatically create all of the 
necessary `began`, `ended`, and `changed` events for whatever poses 
you provide it.
  
  
  
  
Known issues
------------------------------------------------------------------------
Oculus Quest has trouble with digit overlaps as illustrated by the 
[American Sign Language (ASL)](https://en.wikipedia.org/wiki/American_Sign_Language)
poses for **M**, **N**, **R**, **T**, **X**, and so on. This is a 
limitation of the tracking on Oculus’ side so there’s not much we can 
do about that for the moment. Take heart though: the folks over at 
Oculus have been making huge strides in what is a difficult technology 
to wrangle, and I imagine stuff like this is on their to-do list 
already.  
  
  
  
  
A note on repetition
------------------------------------------------------------------------
It’s cleaner, more legible, and easier to debug when you write logic 
once and reuse it rather than copy and paste it multiple times. This 
quickly comes into play when dealing with hands; we often must apply the 
same logic to two things at once. One clean way of doing this is using
an `Array` literal to house the two hands, then use the `Array`’s
[`forEach`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach) 
method to operate on each hand in turn. Note the semicolon prefix before
the `Array` literal. [JavaScript does not require semicolons as line
endings and I do not believe in using them as such because they are 
merely typographic 
clutter.](https://quantumjavascript.app/contributing.html#JavaScript_style)
Because of this it’s somtimes necessary to include a semicolon ahead of
an expression beginning with an `Array` literal to ensure the 
interpreter does not mistake the literal for a property accessor for a 
preceding object.

```javascript

;[ handLeft, handRight ]
.forEach( function( hand ){

hand.addEventListener(

'peace pose began', 
		 onPeacePoseBegan
	)
	hand.addEventListener(

'peace pose ended',
		 onPeacePoseEnded
	)
})

```  
  
  
  
  
Requirements
------------------------------------------------------------------------
This code has been designed for the [Oculus 
Quest](https://www.oculus.com/quest/) headset, though device support
will expand as more devices implement the [WebXR hand tracking 
API](https://immersive-web.github.io/webxr-hand-input/). 
Be sure your Oculus Quest has all of the latest software updates 
installed, including Oculus Browser 15.3.0 or later, then 
follow these steps to experience the demo for yourself:  
  
1. In the main **Settings** menu
navigate to Device → Hands and Controllers.
Enable both **Hand Tracking**
and **Auto Enable Hands or Controllers**.

2. In **Oculus Browser**
visit [chrome://flags/](chrome://flags/) 
and search for “hands” in the flags search box.

3. Within this flags page, 
set the “WebXR experiences with hands tracking” flag
(`#webxr-hands-tracking`)
to **Hands and pointers**.

4. Again, within this flags page,
set the “WebXR experiences with joints tracking” flag
(`#webxr-hands`)
to **Enabled**.

5. Restart Oculus Browser
and visit this demo again.
Use your hand controllers 
to click the “Enter VR” button.
Once you are inside the experience put your controllers down,
hold your hands out in front of you 
so that the headset can see them,
and enjoy! 👍   
  
  
  
  
Colophon
------------------------------------------------------------------------
I’m [Stewart](https://stewartsmith.io). These days I make WebXR things 
and [quantum computing things](https://quantumjavascript.app/) from my
home in Brooklyn, New York. Black lives matter.

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