# 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
---------
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
Co-authored-by: AlephCubed <76791009+AlephCubed@users.noreply.github.com>
# Objective
- Followup to https://github.com/bevyengine/bevy/pull/19633
- As discussed, it's a bit cumbersome to specify that you want the
correct orientation every single time
- Also, glTFs loaded from third parties will still be loaded incorrectly
## Solution
- Allow opting into the new behavior globally or per-asset
- Also improved some docs while on it :)
## Testing
- Ran the animation examples
- Ran the test scene from the last PR with all configuration
combinations
# Objective
*Fixes #5670 as an opt-in for now*
glTF uses the following coordinate system:
- forward: Z
- up: Y
- right: -X
and Bevy uses:
- forward: -Z
- up: Y
- right: X
For the longest time, Bevy has simply ignored this distinction. That
caused issues when working across programs, as most software respects
the
glTF coordinate system when importing and exporting glTFs. Your scene
might have looked correct in Blender, Maya, TrenchBroom, etc. but
everything would be flipped when importing it into Bevy!
## Solution
Add an option to the glTF loader to perform coordinate conversion. Note
that this makes a distinction in the camera nodes, as glTF uses a
different coordinate system for them.
## Follow Ups
- Add global glTF loader settings, similar to the image loader, so that
users can make third-party crates also load their glTFs with corrected
coordinates
- Decide on a migration strategy to make this the future default
- Create an issue
- Get feedback from Patrick Walton and Cart (not pinging them here to
not spam them)
- Include this pic for reference of how Blender assumes -Y as forward:
## Testing
I ran all glTF animation examples with the new setting enabled to
validate that they look the same, just flipped.
Also got a nice test scene from Chris that includes a camera inside the
glTF. Thanks @ChristopherBiscardi!
Blender (-Y forward):
Bevy (-Z forward, but the model looks the wrong way):
Bevy with `convert_coordinates` enabled (-Z forward):
Validation that the axes are correct with F3D's glTF viewer (+Z
forward):
