[idea] Switch to a module system instead of a global namespace, then use the module system to optionally construct a global namespace.

[trusktr]

For example, use CommonJS or ES6 modules for all things. This will help to convert to a properly modular library for NPM.

The advantage of this is that people will be able to require/import certain classes into their projects, and their build tools will compile only those classes, not the entire library, making application more lean.

The user can optionally use THREE as a contain-all by importing three. That would load the project's index.js file, and that file would use CommonJS or ES6 import syntax to load all the other files it needs, and it would export a single object equivalent of what THREE currently is.

Users would also be able to import, say, three/core/Object3D as in

import Object3D from `three/core/Object3D`

or

let Object3D = require('three/core/Object3D')

to import classes directly, and when their program is compiled, only the things they use will be built into their applications.

ES6 modules are an official part of JavaScript now, so it would be super beneficial to convert to those, use semver, and to publish on NPM.

[GGAlanSmithee]

There is a long standing issue about this already - #4776