Command to uncompress KTX2 Textures

[jo-chemla]

Similar to #382 (command to uncompress draco), it would be great to have a gltf-pipeline flag to decompress textures - especially decompressing KTX2 textures which are often used on the web - could then be used on complete tileset tiles 3d-tiles-tools upgrade via the --option flag.

Similar issue on glTF-Blender-IO plugin for KTX2 support is KhronosGroup/glTF-Blender-IO#1896, they are awaiting OpenImageIO support for the KTX format, see here AcademySoftwareFoundation/OpenImageIO#2329

[javagl]

Just to clarify: If the goal here was only to convert KTX textures in an existing tileset into "other" texture types, then this could also be a functionality in the 3d-tiles-tools. There already is some KTX-related functionality, around the KtxUtility class. Currently, this focusses on encoding, but maybe decoding could also be offered.

[jo-chemla]

Thanks for getting back. This can indeed be part of 3d-tlies-tools, although I would have thought this kind of utility would be useful for gltf-pipeline as well in case anyone wanted to apply ktx encode/decode to a static mesh texture(s) rather than all meshes/textures of a tileset. Note gltf-transform just released ktc-decompress transform, which relies on the KTX-Software CLI, see here donmccurdy/glTF-Transform#591

[javagl]

in case anyone wanted to apply ktx encode/decode to a static mesh texture(s) rather than all meshes/textures of a tileset.

The 3D Tiles Tools offer several functionalities that fall into two categories, indicated by the "Command line tools for tilesets" and "Command line tools for tile content" sections of the README. In many cases, the core building block is the tile content operation. In some way (and many cases) the tileset operation is just applying that operation to all contents of a tileset.

(This idea is not applied completely consistently. On the level of the implementation, the structures are already trying to converge to that state. And the "pipeline" functionality is another step in that direction. But more work has to go into that...)

So it would be reasonable to have something like
npx 3d-tiles-tools unpackKtx -i input.glb -o output.glb
for a single glTF, and some command like unpackAllKtxInTileset that just does the same for all GLBs of a tileset.

But... it's never that easy 🙂

The question of "tileset vs. single GLB" is a question of granularity. And ... as granularities go, there are multiple levels. The same could be applied to a single GLB. How fine-grained should the control be, and how exactly should that be offered at the command line? You know, people will want to do things like
"Decompress the KTX-encoded roughness texture of primitive 3 of mesh 5 into a PNG, and its base color texture into a JPG with 70% compression"
and at some point, it just doesn't make sense to try and squeeze that into a CLI.

The https://github.khronos.org/glTF-Compressor-Release/ offers some of that functionality with a UI: Drag-and-drop the model, select the "Compressor" tab at the right, and select the textures and settings individually, or in bulk, maybe based on their type. Still not very accessible for end-users, though: "What should I select here?!" ...