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CesiumGS / 3d-tiles

Specification for streaming massive heterogeneous 3D geospatial datasets :earth_americas:
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Include glTF extensions in tileset extensions list #311

Closed lilleyse closed 2 years ago

lilleyse commented 6 years ago

Should glTF extensions used by embedded glTFs be listed in the tileset JSON somewhere?

Examples: a tileset uses KHR_draco_mesh_compression or KHR_techniques_webgl, which not all implementations may support.

If we decide to add this it would probably be two top level tileset JSON properties called gltfExtensionsUsed and gltfExtensionsRequired.

pjcozzi commented 6 years ago

Would wait to see if this is useful in practice as it couples the tileset JSON and the tiles.

Also, I don't think we should add any new issues labeled 1.0 at this point.

OmarShehata commented 5 years ago

This could be useful for the new WebP glTF extension, where Tilesets that use glTF's with this extension may fail to load on clients that don't implement a fallback.

mramato commented 5 years ago

I recently ran into this as well, being able to get a list of required extensions for b3dm/glTF payloads is pretty critical to writing a generic cross-browser tileset viewer.

OmarShehata commented 5 years ago

Does 3D Tiles contain any other payload that have, or might in the future have extensions? Is it sufficient just to have gltfExtensionsUsed and required? I guess it doesn't matter because if format X in the future has extensions we can add XExtensionsUsed at that point then?

lilleyse commented 4 years ago

More generally should a tileset list the glTF features in use (if that can even be defined)? Should all 3D Tiles clients be expected to support the full glTF feature set?

This topic came up on the forum: https://community.cesium.com/t/should-3d-tiles-spec-formalize-gltf-restrictions/9667/2

fortgreeneVR commented 4 years ago

How would a viewer implement forward compatibility? It seems it would be up to the 3D Tiles / glTF author to suggest fallback options for viewers that can't handle certain (new) features. Like a shader author that implements fallbacks for older hardware. It would be nice if there was a mechanism for 3D Tiles authors to do this. Would that be a unique capability for 3D file formats?

ptrgags commented 2 years ago

This was included in the 3DTILES_content_gltf extension, see this section