removeExtension on document

[jo-chemla]

Hi there,

I'm trying to decompress ktx2 textures to png for a bunch of glb mesh tiles of a 3d-tiles tileset. I'm relying on the ktx extract CLI to do so and 3d-tiles-tools tilesetProcessor.processTileContentEntries, more context and code sample here.

Thanks to targetDocument.transform( customTransform({}), ), I can

• convert all ktx textures to png,
• set their mimeType to image/png,
• and correctly reference these new png images in the output document.

However, this resulting document still has the KHR_texture_basisu extension referenced as extensionsUsed and extensionsRequired. If I manually remove them from the glb->gltf json, blender_gltf_io plugin can import the resulting mesh with texture perfectly.

I've tried multiple iterations of document root scene traversing all children, but logging listExtensions() on each of these returns only empty arrays. I therefore assume I have to manually remove the extension from the gltf document itselft. I can set the extension to null on the texture or document root via texture.setExtension('KHR_texture_basisu', null), but could not find the equivalent to remove an extension on the document.

The last resort I can think of is using io.writeJSON(document, {}).then(jsonDoc and remove extensions directly on the json object, before writing back to binary. I would love it if there are simpler alternatives. Thanks a lot for your help!

[jo-chemla]

Self replying here in case anyone stumbles on this discussion: This bit let me find what I was missing, extension.dispose();

        document.getRoot()
            .listExtensionsUsed()
            .find((e) => e.extensionName === 'KHR_texture_basisu')
            ?.dispose();

[donmccurdy]

Yes, this is what I'll usually do. Disposing the root-level extension will also remove any extension-specific properties attached elsewhere (though there are none in the case of KHR_texture_basisu).

Probably less intuitive to use createExtension for an existing extension, but this will have the same effect:

import { KHRTextureBasisu } from '@gltf-transform/extensions';

document.createExtension(KHRTextureBasisu).dispose();

[jo-chemla]

Ah good to also know this createExtension().dispose, thanks as always!