WebGPURenderer: Add Offscreen Support

[RenaudRohlinger]

This PR fix the use of the WebGPURenderer in a worker context.

A small issue is that the WebGPURenderer is intricately tied to direct imports from 'three' making it complex to create an example without changing the configuration of the project.
Web browsers do not currently support the importmap feature in worker contexts. Alternatives would be to update the rollup configuration or use relatives paths. (Uncaught (in promise) TypeError: Failed to resolve module specifier "three". Relative references must start with either "/", "./", or "../".)

I tested on my local with another project on both backends and it works fine.

This contribution is funded by Utsubo

[sunag]

Web browsers do not currently support the importmap feature in worker contexts. Alternatives would be to update the rollup configuration or use relatives paths. (Uncaught (in promise) TypeError: Failed to resolve module specifier "three". Relative references must start with either "/", "./", or "../".)

Sorry, I didn't quite understand the relationship between the description and the commit.

[RenaudRohlinger]

I wanted to add an example for webgpu_offscreen but it's currently not possible with the WebGPURenderer being in examples/jsm.

The PR by itself simply adds Worker support. 😁

[sunag]

Maybe you didn't choose other commits by mistake?

[RenaudRohlinger]

Indeed that was my bad @sunag. Basically injecting a promise outside of the scope of the module breaks web workers. So I refactored:

// statics

let _staticAdapter = null;

if ( navigator.gpu !== undefined ) {

	_staticAdapter = await navigator.gpu.requestAdapter(); <-- this breaks web workers

}

to:

// statics

let isAvailable = navigator.gpu !== undefined;


if ( typeof window !== 'undefined' && isAvailable ) {

	isAvailable = await navigator.gpu.requestAdapter();

}

Using navigator.gpu in order to check if WebGPU is available in the worker is not a perfect solution but it's very decent and a lot better than nothing!

Alternative solution would have been to make isAvailable or/and the WebGPURenderer an async function which is too much of a breaking change IMO.

[sunag]

Thanks for the detailed explanation. :)