Add MSFT_texture_xnb extension

[dellis1972]

This extension adds the ability to specify textures using the XNA Binary format (XNB). An implementation of this extension can use the textures provided in the XNB files as an alternative to the PNG or JPG textures available in glTF 2.0.

This extension is used by users of XNA like frameworks such as MonoGame,FNA and KNI to load glTF files at runtime by including XNB textures.

[lexaknyazev]

XNA is not a registered vendor prefix. IIRC, it's not an active MS trademark anymore.

If MonoGame can reasonably "own" it, please create an issue with a prefix registration request (see https://github.com/KhronosGroup/glTF/blob/main/extensions/Prefixes.md). In a case of any legal reasons preventing MonoGame from owning the XNA prefix, please register another prefix and rename the extension.

[dellis1972]

@lexaknyazev

I was going to make this a MSFT_texture_xnb but I wasn't sure if I could reasonably do that (even though I do work at MS).
Does the Prefix "owner" have to own the file format?

[lexaknyazev]

Does the Prefix "owner" have to own the file format?

That's not our concern. The extension spec and the prefix should be owned by the same entity (unless it's EXT, which implies some level of multi-vendor interoperability).

@bghgary WDYT?

[bghgary]

I'm not aware of any rules from Khronos or Microsoft against putting it as MSFT prefix, but I'm not sure it makes sense since XNA is not being advanced by Microsoft. @dellis1972 Is XNB owned by some entity? Is there a spec for it? I did a quick search and didn't see anything obvious. Feel free to ping me internally if you want to chat.

[dellis1972]

I'm not aware of any rules from Khronos or Microsoft against putting it as MSFT prefix, but I'm not sure it makes sense since XNA is not being advanced by Microsoft. @dellis1972 Is XNB owned by some entity? Is there a spec for it? I did a quick search and didn't see anything obvious. Feel free to ping me internally if you want to chat.

The Spec is licences to Microsoft. This is a link to the doc on the format. Its a backup from the original MS doc.
https://github.com/SimonDarksideJ/XNAGameStudio/blob/archive/Samples/XNA_XNB_Format/XNB%20Format.docx

[bghgary]

If it's a Microsoft spec, then MSFT prefix sounds fine to me. This glTF extension should be specific and point to this XNB spec. If this XNB spec ever advances, we will need a new glTF extension.

[lexaknyazev]

I'd strongly suggest hosting that document in a more permanent place than someone's personal GitHub repo.

[dellis1972]

I'd strongly suggest hosting that document in a more permanent place than someone's personal GitHub repo.

The spec used to be hosted on MS servers at one point. I'll chat with the MonoGame maintainers , see if we can host it on our website.

[dellis1972]

So I think this is good to go. We are just waiting on moving the docx for the XNA format to the monogame docs site, so I can link it in this PR.