# 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):
9b743d2a43