## Motivation
The GLTF (`.gltf`, `.glb`) 3D model format is very popular for game development and visual productions.
For an indie game studio, it would be convenient for a team to view textured 3D models directly from the Forgejo interface (otherwise they need to be downloaded and opened). [Perforce](https://www.perforce.com/products/helix-dam), [Diversion](https://www.diversion.dev/), and GitHub all have this capability to differing extents.
Some discussion on 3D file support here: https://codeberg.org/forgejo/forgejo/issues/5188
## Changes
Adds a model viewer similar to [GitHub STL viewer](https://github.com/assimp/assimp/blob/master/test/models/STL/Spider_ascii.stl) for `.glb` model files, and lays some groundwork to support future files. Uses the [model-viewer](https://modelviewer.dev/) library by Google and three.js. The model viewer is interactive and can be rotated and scaled.
## How to Test
1) Create a new repository or use an existing one.
2) Upload a `.glb` file such as `tests/testdata/data/viewer/Unicode❤♻Test.glb` (CC0 1.0 Universal)
3) View the file in the repository.
- Similar to image files, the 3D model should be rendered in a viewer.
- Use mouse clicks to turn and zoom.
## Licenses
Libraries used for this change include three.js and @google/model-viewer, which are MIT and Apache-2.0 licenses respectively. Both of these are compatible with Forgejo's GPL3.0 license.
## Future Plans
1) `.gltf` was not attempted because it is a multiple file format, referencing other files in the same directory. Still need to experiment with this to see if it can work. `.glb` is a single file containing a `.gltf` and all of its other file/texture dependencies so was easier to implement.
2) The PR diff still shows the model as an unviewable bin file, but clicking the "View File" button takes you to a view screen where this model viewer is used. It would be nice to view the before and after of the model in two side-by-side model viewers, akin to reviewing a change in an image.
3) Also inserted stubs for adding contexts for GLTF, STL, OBJ, and 3MF. These ultimately don't do anything yet as only `.glb` files can be detected by the type sniffer of all of these.
## Checklist
The [contributor guide](https://forgejo.org/docs/next/contributor/) contains information that will be helpful to first time contributors. There also are a few [conditions for merging Pull Requests in Forgejo repositories](https://codeberg.org/forgejo/governance/src/branch/main/PullRequestsAgreement.md). You are also welcome to join the [Forgejo development chatroom](https://matrix.to/#/#forgejo-development:matrix.org).
### Tests
- I added test coverage for checking GLB file content using the first few bytes.
- [x] in their respective `typesniffer_test.go` for unit tests.
### Documentation
- [ ] I created a pull request [to the documentation](https://codeberg.org/forgejo/docs) to explain to Forgejo users how to use this change.
- [x] I did not document these changes and I do not expect someone else to do it.
### Release notes
- [ ] I do not want this change to show in the release notes.
- [ ] I want the title to show in the release notes with a link to this pull request.
- [ ] I want the content of the `release-notes/<pull request number>.md` to be be used for the release notes instead of the title.
<!--start release-notes-assistant-->
## Release notes
<!--URL:https://codeberg.org/forgejo/forgejo-->
- User Interface features
- [PR](https://codeberg.org/forgejo/forgejo/pulls/8111): <!--number 8111 --><!--line 0 --><!--description YWRkIG1vZGVsIHZpZXdlciBmb3IgYC5nbGJgIChHTFRGKSBtb2RlbCBpbiBmaWxlIHZpZXc=-->add model viewer for `.glb` (GLTF) model in file view<!--description-->
<!--end release-notes-assistant-->
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/8111
Reviewed-by: oliverpool <oliverpool@noreply.codeberg.org>
Co-authored-by: Alex Smith <amsmith.pro@pm.me>
Co-committed-by: Alex Smith <amsmith.pro@pm.me>
