KTX2Loader: Support loading uncompressed DataTexture and Data3DTexture

[donmccurdy]

Adds support for loading KTX 2.0 textures in uncompressed formats. With #24102, THREE.KTX2Exporter (new) can export DataTexture and Data3DTexture instances to these formats.

✅ Included:

• Outputs: THREE.DataTexture or THREE.Data3DTexture
• Types: UnsignedByteType, HalfFloatType, or FloatType
• Formats: RGBAFormat, RGFormat, or RedFormat
• Encodings: LinearEncoding or sRGBEncoding

⚠️ Not included:

• GPU compression formats (ETC2, ASTC, etc.)
• Supercompression (BasisLZ, ZSTD, ZLIB)

❌ Breaking change:

• loader.load( 'path/to/texture.ktx2', onLoad ) no longer returns a CompressedTexture instance synchronously, because we cannot know in advance whether the return type will be CompressedTexture, DataTexture, or Data3DTexture. A callback or the async pattern, const texture = await loader.loadAsync( 'path/to/texture.ktx2' ), should be used instead.

See #24102 for more details.

[mrdoob]

Seems like webgl_loader_gltf_compressed is failing? 🤔

[donmccurdy]

I'm seeing alternating failures in CI for:

• webgl_loader_gltf_compressed
• webgl_loader_texture_ktx2

But both look OK locally... a bit confused what might have broken here. Do these examples break locally for anyone else?

[Mugen87]

Do these examples break locally for anyone else?

I've downloaded your branch and tested both examples on my iMac (macOS, Chrome 102.0.5005.61). They break with the following error:

Uncaught SyntaxError: The requested module '../libs/ktx-parse.module.js' does not provide an export named 'VK_FORMAT_R16G16B16A16_SFLOAT'

[donmccurdy]

Ah thanks! This depended on the ktx-parse.module.js update from #24102, I guess I had the file symlinked. Should be fixed now. 👍

[Mugen87]

Both examples work now 🎉 .

[mrdoob]

Thanks!

[mrdoob]

Is this expected? 🤔

[Mugen87]

I could imagine that the js version of KTX2Loader does not work with the new import from ../libs/ktx-parse.module.js.

There is no js version of KTX2Exporter. Should we do the same KTX2Loader?

[LeviPesin]

I think maybe it is already time to remove examples/js (and consequently other builds than three.module.js)?
(As we now do not convert new files in examples/jsm)

[Mugen87]

We have stated in #20568 (comment) that examples/js will be kept until all major browsers support import maps. I don't think there is a reason to start a discussion about this topic again.

[donmccurdy]

Originally KTX2Loader was added without an examples/js version, we added it in #22485 to unblock aframevr/aframe#4919 for A-Frame. That support didn't end up making it into A-Frame yet, so maybe not a problem to revert it.

At some point I would like to get KTX2Loader working with much smaller/lighter wasm dependencies, and we will need the ktx-parse dependency for that (with or without this DataTexture / Data3DTexture support). I guess the alternative to support examples/js would be to inline ktx-parse.module.js separately into KTX2Loader and KTX2Exporter, not ideal but possible.

[Mugen87]

Is there a UMD version of ktx-parse? If so, you could change the import in examples/jsm/loaders/KTX2Loader.js to something like:

import * as ktxParse from '../libs/ktx-parse.module.js';

Assuming ktxParse is the namespace from the UMD version. This approach is used by other loaders, too.

I'm also fine with inlining ktx-parse or completely removing examples/js/loaders/KTX2Loader.js.

[donmccurdy]

I don't include a UMD module with the ktx-parse npm package, but it shouldn't be a problem to generate one for the three.js package. Probably easier than generating an inline-friendly version of the library.

[donmccurdy]

• /cc KTX2Loader: Add UMD ktx-parse build #24260