EXRExporter: initial version

[sciecode]

Rebase of #19764

Initial PR with basic functionalities adjusted & proper support for HalfFloatType and FloatType renderTargets.

Removed encoding workarounds, as only LinearEncoding is expected.

---

Usage Example

import { EXRExporter } from './jsm/exporters/EXRExporter.js';

function downloadEXR( buffer ) {
   const blob = new Blob([buffer.buffer], {type: "image/x-exr"}),
   const url = window.URL.createObjectURL(blob);
   const a = document.createElement("a");
   a.href = url;
   a.style = "display: none";
   a.download = 'render.exr';
   document.body.appendChild(a);
   a.click();
   window.URL.revokeObjectURL(url);
};

...

const exporter = new EXRExporter();
downloadEXR( exporter.parse( renderer, renderTarget ) ); //sync - because readPixels async not yet available.

if there isn't any API changes suggested, should be ready to merge.

[WestLangley]

Great! I Successfully used this to export a computed PMREM to .exr format, and then reload the exported PMREM as a CubeUV environment map.

Thing is, I would have expected an EXR exporter to take as an argument a data texture -- not a render target. 🤔

[sciecode]

Great! I Successfully used this to export a computed PMREM to .exr format, and then reload the exported PMREM as a CubeUV environment map.

Thing is, I would have expected an EXR exporter to take as an argument a data texture -- not a render target. 🤔

I'm sure we can do both 😄

Will implement method for dealing with DataTexture API on future PR. Users will just need to be careful about supplying HalfFloat pixel as Uint16Array. But the same would be needed for WebGL side, so no big surprise there.

[mrdoob]

Thanks!