BENTLEY_primitive_restart

[pmconne]

This extension permits the prohibition against maximal index values in index buffers to be selectively relaxed for groups of primitives, while providing a trivial fallback for implementations that don't support primitive restart. Discussed in #1142.

[lexaknyazev]

Please update this line to say 2025 and the actual copyright holder.

[pmconne]

@pjcozzi any guidance on copyright and license here? The extension template includes this placeholder, but only one vendor extension actually includes it.

[pjcozzi]

@rudybear can you confirm if extensions should have a copyright comment? If so, is it copyright Khronos?

[lexaknyazev]

It's a part of REUSE compliance. All files must have such comments (if some don't we should fix that).

[lexaknyazev]

A vendor-prefixed extension should be owned by the vendor. Khronos usually owns extensions with KHR and EXT prefixes.

[lexaknyazev]

@emackey @javagl
What do you think about making this an EXT extension? It seems quite trivial to support it in viewers.

Also since it extends mesh objects, should it be called *_mesh_primitive_restart?

[javagl]

^{Disclosure: I'm an independent contributor, but also a freelancer with a connection to Bentley. I do not speak on behalf of either side here. I also have not yet reviewed this extension proposal on a technical level (only causally watching the comments and discussions).}

Only about the naming:

Whether the prefix is BENTEY or EXT is up do decide for the person who proposes the extension.

(Although some of the extension development process is about to be refined, the section at https://github.com/KhronosGroup/glTF/tree/main/extensions#naming will likely still be kept in a similar form. One addition here might be that the EXT prefix suggests some broad, general applicability or that the extension is not bound to any form of ~"vendor-specific functionality" - but that's very vague...)

The naming section also says

Names SHOULD be structured as <PREFIX>_<scope>_<feature>, where scope is an existing glTF concept (e.g. mesh, texture, image)

It is not entirely clear whether that only refers to top-level elements (somehow related to the point of gltfProperty vs. glTFChildOfRootProperty above), and whether any "sub-element" should be part of the name.

One could make a case to always include the "top-level" element name. Be it at least for the case that someone defines an extension that goes into an animation.sampler, and we want to make sure that it is called EXT_animation_sampler_example, and not just EXT_sampler_example, which would cause an ambiguity with the top-level sampler.

So I'd be leaning towards _mesh_primitive_restart here.

[pmconne]

Whether the prefix is BENTEY or EXT is up do decide for the person who proposes the extension.

If there's no objection, I will push a change to rename the extension to EXT_mesh_primitive_restart and assign the copyright to Khronos.

[bghgary]

Should we just name it KHR_ directly? We have already ratified some EXT_ extensions and wasn't able to rename to KHR_ due to compatibility. Would we ever consider ratifying this extension?

[lexaknyazev]

Should we just name it KHR_ directly?

We'd have to get an agreement within 3DF WG first and commit to providing Sample Assets at least.

[pjcozzi]

Should we just name it KHR_ directly?

We'd have to get an agreement within 3DF WG first and commit to providing Sample Assets at least.

@lexaknyazev @bghgary any update on this? Or any additional feedback for @pmconne?