Add BasisTextureLoader

[donmccurdy]

Basis Universal announcement. 🎉

Thanks to @shrekshao and @austinEng for their help with the WASM transcoder and WebGL integration, and to Binomial for the Basis universal format and tooling (GitHub).

The loader in this PR is similar to the one used in the Basis demos, with some enhancements. Transcoding is handled in a Web Worker, and multiple textures can be transcoded in parallel with multiple workers. Several TODOs remain in the code. I plan to fix them, but the loader is functional in the meantime.

Basis will be the foundation for compressed texture support in glTF, per Khronos blog post.

[takahirox]

Nice work. Will an example (examples/webgl_texture_basis.html or something) be in another PR?

[donmccurdy]

Probably another PR, yeah. In the meantime:

const loader = new THREE.BasisTextureLoader();

// Order doesn't matter. Detecting supported formats requires
// a WebGL context. The transcoder path should contain a
// JS wrapper and WASM binary with predetermined names. The
// maxWorkers option is used to avoid conflicts with other
// application services that may need workers.
loader.detectSupport( renderer );
loader.setTranscoderPath( './basis/' );
loader.setMaxWorkers( 4 );

loader.load( './assets/diffuse.basis', ( texture ) => {

	material.map = texture;
	
	render();

} );

Just realized I didn't add the setMaxWorkers method yet.

[takahirox]

OK, looking forward to seeing an example. And thanks for sharing API.

[titansoftime]

I'm excited to try this!

[mrdoob]

Thanks!

[donmccurdy]

Opened #16524 to track next steps on this loader.