bevy/crates/bevy_gltf
Alice Cecile a304fd9a99 Split bevy_hierarchy out from bevy_transform (#4168)
# Objective

- Hierarchy tools are not just used for `Transform`: they are also used for scenes.
- In the future there's interest in using them for other features, such as visiibility inheritance.
- The fact that these tools are found in `bevy_transform` causes a great deal of user and developer confusion
- Fixes #2758.

## Solution

- Split `bevy_transform` into two!
- Make everything work again.

Note that this is a very tightly scoped PR: I *know* there are code quality and docs issues that existed in bevy_transform that I've just moved around. We should fix those in a seperate PR and try to merge this ASAP to reduce the bitrot involved in splitting an entire crate.

## Frustrations

The API around `GlobalTransform` is a mess: we have massive code and docs duplication, no link between the two types and no clear way to extend this to other forms of inheritance.

In the medium-term, I feel pretty strongly that `GlobalTransform` should be replaced by something like `Inherited<Transform>`, which lives in `bevy_hierarchy`:

- avoids code duplication
- makes the inheritance pattern extensible
- links the types at the type-level
- allows us to remove all references to inheritance from `bevy_transform`, making it more useful as a standalone crate and cleaning up its docs

## Additional context

- double-blessed by @cart in https://github.com/bevyengine/bevy/issues/4141#issuecomment-1063592414 and https://github.com/bevyengine/bevy/issues/2758#issuecomment-913810963
- preparation for more advanced / cleaner hierarchy tools: go read https://github.com/bevyengine/rfcs/pull/53 !
- originally attempted by @finegeometer in #2789. It was a great idea, just needed more discussion!

Co-authored-by: Carter Anderson <mcanders1@gmail.com>
2022-03-15 01:54:05 +00:00
..
src Split bevy_hierarchy out from bevy_transform (#4168) 2022-03-15 01:54:05 +00:00
Cargo.toml Split bevy_hierarchy out from bevy_transform (#4168) 2022-03-15 01:54:05 +00:00