Support toJSON in Quaternion class

[XorTdsc]

Description

Similarly to this request it would be nice to have a clean toJSON serialization for the Quaternion class. Currently the JSON.stringify() results in
{"isQuaternion":true,"_x":0,"_y":0,"_z":0,"_w":1}

Solution

The preferred output should be
{"x":0,"y":0,"z":0,"w":1}

Alternatives

Probably not a viable alternative: Maybe a serialization toolset in a separate class/lib ?

Additional context

No response

[Mugen87]

I'm fine with adding toJSON() to Quaternion. Especially since Color already has a toJSON() method, too.

[donmccurdy]

Maybe as an array, like [0, 0, 0, 1]? If we added toJSON on Matrix3 and Matrix4 later they'd be arrays, might as well be consistent.

[Mugen87]

I'm fine with arrays, too. In the three.js JSON Object/Scene format, matrix and vector properties like the local matrix or the center of a bounding sphere are already serialized as arrays.

[XorTdsc]

I guess that's fine too, as long as everything is consistent (currently Vector3 does not export as an array)

[epreston]

You can get what you are after by calling toArray on the quaternion.

const quat = new Quaternion(); 
// change rotation
const json = JSON.stringify( quat.toArray() )

When you read it back in use fromArray

const data = JSON.parse( json )
const quatFromJson = new Quaternion().fromArray( data ); 

Vector3 currently has 'to' and 'from' array methods.

You might find it's less than optimal as a storage representation for the same information.

[Mugen87]

The problem with this suggestion is that you often can't execute such code since the JSON serialization happens indirectly when performing certain operations.

Having a toJSON() implementation solve this as well.