# Objective
*Step towards https://github.com/bevyengine/bevy/issues/19686*
We now have all the infrastructure in place to migrate Bevy's default
behavior when loading glTF files to respect their coordinate system.
Let's start migrating! For motivation, see the issue linked above
## Solution
- Introduce a feature flag called `gltf_convert_coordinates_default`
- Currently,`GltfPlugin::convert_coordinates` defaults to `false`
- If `gltf_convert_coordinates_default` is enabled,
`GltfPlugin::convert_coordinates` will default to `true`
- If `gltf_convert_coordinates_default` is not enabled *and*
`GltfPlugin::convert_coordinates` is false, we assume the user is
implicitly using the old behavior. Print a warning *once* in that case,
but only when a glTF was actually loaded
- A user can opt into the new behavior either
- Globally, by enabling `gltf_convert_coordinates_default` in their
`Cargo.toml`
- Globally, by enabling `GltfPlugin::convert_coordinates`
- Per asset, by enabling `GltfLoaderSettings::convert_coordinates`
- A user can explicitly opt out of the new behavior and silence the
warning by
- Enabling `gltf_convert_coordinates_default` in their `Cargo.toml` and
disabling `GltfPlugin::convert_coordinates`
- This PR also moves the existing release note into a migration guide
Note that I'm very open to change any features, mechanisms, warning
texts, etc. as needed :)
## Future Work
- This PR leaves all examples fully functional by not enabling this flag
internally yet. A followup PR will enable it as a `dev-dependency` and
migrate all of our examples involving glTFs to the new behavior.
- After 0.17 (and the RC before) lands, we'll gather feedback to see if
anything breaks or the suggested migration is inconvenient in some way
- If all goes well, we'll kill this flag and change the default of
`GltfPlugin::convert_coordinates` to `true` in 0.18
## Testing
- Ran examples with and without the flag
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Co-authored-by: Carter Anderson <mcanders1@gmail.com>
Co-authored-by: AlephCubed <76791009+AlephCubed@users.noreply.github.com>
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