Should 3D Tiles spec formalize GLTF restrictions?

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I’ve brought this up in a private email already, but I wanted to make the point in this forum as well.

I’m wondering if it would make sense to formalize some restrictions on the nature of the glTF embedded in b3dm and i3dm tiles.

The glTF format supports a wide range of possible content structure but most of it seems at odds with the intent of 3D Tiles. To give a simple example, I could have a tileset with 1 node that contains a b3dm, which contains a glTF file with a hierarchy of many meshes. This use is not against the letter of the 3D Tiles spec but hardly in its spirit.

Of course someone who wants to support 3D tiles could simply restrict themselves to a subset of glTF possibilities, but that does not seem to be in the spirit of open standards.

I’m curious what other forum participants think about this.
Thanks.

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Hey @fortgreeneVR. I lean towards no restrictions on glTF unless it conflicts with 3D Tiles in some way. I’ve yet to see node animations, skinning, or morph targets in 3D Tiles but I wouldn’t want to restrict anyone from doing that.

I think a compromise would be for a tileset to list all the glTF features it uses so that clients can know whether they can display the tileset. Same with glTF extensions (https://github.com/CesiumGS/3d-tiles/issues/311). I’m not sure what the list of features would be though.

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