Revive model index

[javagl]

The glTF-Sample-Models repo contained a model-index.json file that contained information about all available models and variants. This index file was generated with the generate-index.py script.

I have seen the allModels.json that also lists all models, but it does not list the variants, file names, and screenshot names.

I think that the model-index.json should still exist somewhere. Otherwise, all the tools that rely on this file would be broken.

Some options:

• Add the missing information about the variants in the allModels.json.
  • This would still be a brekaing change for toolchains that already rely on the model-index.json
• Add the tags as they are currently contained in the allModels.json to the model-index.json. This would be backward-compatible: Tools that already read the model-index.json would just ignore the tags.

Further options (depending on the choice above):

• Extend the current PHP code to generate the information from the model-index.json, including the tags
• Use the original generate-index.py to generate the model-index.json, and extend that to include the tags there

We could have both, the allModels.json and the model-index.json, but having only one source of truth would certainly be easier to maintain. (And in any case: This source of truth could be updated automatically with GitHub actions after PullRequests)

[DRx3D]

I am inclined to extend generate-index.py to handle the tags for the reasons you list and only create one "index" file.

The location (.../2.0/) from the old repo does not exist. I am thinking the model-index.json file is best in the Models directory as it only refers to models. I am also thinking of adding all README collections that are now at the root level to the Models directory.

[DRx3D]

The latest PR now updated model-index.json and removed allModels.json.

@javagl : Please verify that the repo correctly reflects the intent of this PR.

[javagl]

I have not looked at the details of the code that generates the model-index.json now, but the current output looks like it indeed makes this PR obsolete.