# Objective
Animation docs could use some clarification regarding:
- how exactly curves are evaluated
- how additive blend nodes actually work
## Solution
Add some documentation that explains how curve domains are used and how
additive blend nodes treat their children.
## Commentary
The way additive blend nodes work right now is a little bit weird, since
their first child's weight is ignored. Arguably this makes sense, since
additive animations are authored differently from ordinary animations,
but it also feels a bit strange. We could make the first node's weight
actually be applied, and the present behavior would be recovered when
the weight is set to 1.
The main disadvantage of how things are set up now is that combining a
bunch of additive animations without a base pose is pretty awkward (e.g.
to add them onto a base pose later in the graph). If we changed it, the
main downside would be that reusing the same animation on different
parts of the graph is harder; on the other hand, the weights can be
locally reassigned by using blend nodes with no other children, which
rectifies this shortfall.
# Objective
- Closes#15717
## Solution
- Wrap the handle in a new wrapper component: `AnimationGraphHandle`.
## Testing
Searched for all instances of `AnimationGraph` in the examples and
updated and tested those
## Migration Guide
`Handle<AnimationGraph>` is no longer a component. Instead, use the
`AnimationGraphHandle` component which contains a
`Handle<AnimationGraph>`.
*Additive blending* is an ubiquitous feature in game engines that allows
animations to be concatenated instead of blended. The canonical use case
is to allow a character to hold a weapon while performing arbitrary
poses. For example, if you had a character that needed to be able to
walk or run while attacking with a weapon, the typical workflow is to
have an additive blend node that combines walking and running animation
clips with an animation clip of one of the limbs performing a weapon
attack animation.
This commit adds support for additive blending to Bevy. It builds on top
of the flexible infrastructure in #15589 and introduces a new type of
node, the *add node*. Like blend nodes, add nodes combine the animations
of their children according to their weights. Unlike blend nodes,
however, add nodes don't normalize the weights to 1.0.
The `animation_masks` example has been overhauled to demonstrate the use
of additive blending in combination with masks. There are now controls
to choose an animation clip for every limb of the fox individually.
This patch also fixes a bug whereby masks were incorrectly accumulated
with `insert()` during the graph threading phase, which could cause
corruption of computed masks in some cases.
Note that the `clip` field has been replaced with an `AnimationNodeType`
enum, which breaks `animgraph.ron` files. The `Fox.animgraph.ron` asset
has been updated to the new format.
Closes#14395.
## Showcase
https://github.com/user-attachments/assets/52dfe05f-fdb3-477a-9462-ec150f93df33
## Migration Guide
* The `animgraph.ron` format has changed to accommodate the new
*additive blending* feature. You'll need to change `clip` fields to
instances of the new `AnimationNodeType` enum.
This is an updated version of #15530. Review comments were addressed.
This commit changes the animation graph evaluation to be operate in a
more sensible order and updates the semantics of blend nodes to conform
to [the animation composition RFC]. Prior to this patch, a node graph
like this:
```
┌─────┐
│ │
│ 1 │
│ │
└──┬──┘
│
┌───────┴───────┐
│ │
▼ ▼
┌─────┐ ┌─────┐
│ │ │ │
│ 2 │ │ 3 │
│ │ │ │
└──┬──┘ └──┬──┘
│ │
┌───┴───┐ ┌───┴───┐
│ │ │ │
▼ ▼ ▼ ▼
┌─────┐ ┌─────┐ ┌─────┐ ┌─────┐
│ │ │ │ │ │ │ │
│ 4 │ │ 6 │ │ 5 │ │ 7 │
│ │ │ │ │ │ │ │
└─────┘ └─────┘ └─────┘ └─────┘
```
Would be evaluated as (((4 ⊕ 5) ⊕ 6) ⊕ 7), with the blend (lerp/slerp)
operation notated as ⊕. As quaternion multiplication isn't commutative,
this is very counterintuitive and will especially lead to trouble with
the forthcoming additive blending feature (#15198).
This patch fixes the issue by changing the evaluation order to
postorder, with children of a node evaluated in ascending order by node
index.
To do so, this patch revamps `AnimationCurve` to be based on an
*evaluation stack* and a *blend register*. During target evaluation, the
graph evaluator traverses the graph in postorder. When encountering a
clip node, the evaluator pushes the possibly-interpolated value onto the
evaluation stack. When encountering a blend node, the evaluator pops
values off the stack into the blend register, accumulating weights as
appropriate. When the graph is completely evaluated, the top element on
the stack is *committed* to the property of the component.
A new system, the *graph threading* system, is added in order to cache
the sorted postorder traversal to avoid the overhead of sorting children
at animation evaluation time. Mask evaluation has been moved to this
system so that the graph only has to be traversed at most once per
frame. Unlike the `ActiveAnimation` list, the *threaded graph* is cached
from frame to frame and only has to be regenerated when the animation
graph asset changes.
This patch currently regresses the `animate_target` performance in
`many_foxes` by around 50%, resulting in an FPS loss of about 2-3 FPS.
I'd argue that this is an acceptable price to pay for a much more
intuitive system. In the future, we can mitigate the regression with a
fast path that avoids consulting the graph if only one animation is
playing. However, in the interest of keeping this patch simple, I didn't
do so here.
[the animation composition RFC]:
https://github.com/bevyengine/rfcs/blob/main/rfcs/51-animation-composition.md
# Objective
- Describe the objective or issue this PR addresses.
- If you're fixing a specific issue, say "Fixes #X".
## Solution
- Describe the solution used to achieve the objective above.
## Testing
- Did you test these changes? If so, how?
- Are there any parts that need more testing?
- How can other people (reviewers) test your changes? Is there anything
specific they need to know?
- If relevant, what platforms did you test these changes on, and are
there any important ones you can't test?
---
## Showcase
> This section is optional. If this PR does not include a visual change
or does not add a new feature, you can delete this section.
- Help others understand the result of this PR by showcasing your
awesome work!
- If this PR adds a new feature or public API, consider adding a brief
pseudo-code snippet of it in action
- If this PR includes a visual change, consider adding a screenshot,
GIF, or video
- If you want, you could even include a before/after comparison!
- If the Migration Guide adequately covers the changes, you can delete
this section
While a showcase should aim to be brief and digestible, you can use a
toggleable section to save space on longer showcases:
<details>
<summary>Click to view showcase</summary>
```rust
println!("My super cool code.");
```
</details>
## Migration Guide
> This section is optional. If there are no breaking changes, you can
delete this section.
- If this PR is a breaking change (relative to the last release of
Bevy), describe how a user might need to migrate their code to support
these changes
- Simply adding new functionality is not a breaking change.
- Fixing behavior that was definitely a bug, rather than a questionable
design choice is not a breaking change.
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
Fixes#15541
A bunch of lifetimes were added during the Assets V2 rework, but after
moving to async traits in #12550 they can be elided. That PR mentions
that this might be the case, but apparently it wasn't followed up on at
the time.
~~I ended up grepping for `<'a` and finding a similar case in
`bevy_reflect` which I also fixed.~~ (edit: that one was needed
apparently)
Note that elided lifetimes are unstable in `impl Trait`. If that gets
stabilized then we can elide even more.
## Solution
Remove the extra lifetimes.
## Testing
Everything still compiles. If I have messed something up there is a
small risk that some user code stops compiling, but all the examples
still work at least.
---
## Migration Guide
The traits `AssetLoader`, `AssetSaver` and `Process` traits from
`bevy_asset` now use elided lifetimes. If you implement these then
remove the named lifetime.
# Objective
- Fixes#6370
- Closes#6581
## Solution
- Added the following lints to the workspace:
- `std_instead_of_core`
- `std_instead_of_alloc`
- `alloc_instead_of_core`
- Used `cargo +nightly fmt` with [item level use
formatting](https://rust-lang.github.io/rustfmt/?version=v1.6.0&search=#Item%5C%3A)
to split all `use` statements into single items.
- Used `cargo clippy --workspace --all-targets --all-features --fix
--allow-dirty` to _attempt_ to resolve the new linting issues, and
intervened where the lint was unable to resolve the issue automatically
(usually due to needing an `extern crate alloc;` statement in a crate
root).
- Manually removed certain uses of `std` where negative feature gating
prevented `--all-features` from finding the offending uses.
- Used `cargo +nightly fmt` with [crate level use
formatting](https://rust-lang.github.io/rustfmt/?version=v1.6.0&search=#Crate%5C%3A)
to re-merge all `use` statements matching Bevy's previous styling.
- Manually fixed cases where the `fmt` tool could not re-merge `use`
statements due to conditional compilation attributes.
## Testing
- Ran CI locally
## Migration Guide
The MSRV is now 1.81. Please update to this version or higher.
## Notes
- This is a _massive_ change to try and push through, which is why I've
outlined the semi-automatic steps I used to create this PR, in case this
fails and someone else tries again in the future.
- Making this change has no impact on user code, but does mean Bevy
contributors will be warned to use `core` and `alloc` instead of `std`
where possible.
- This lint is a critical first step towards investigating `no_std`
options for Bevy.
---------
Co-authored-by: François Mockers <francois.mockers@vleue.com>
This commit adds support for *masks* to the animation graph. A mask is a
set of animation targets (bones) that neither a node nor its descendants
are allowed to animate. Animation targets can be assigned one or more
*mask group*s, which are specific to a single graph. If a node masks out
any mask group that an animation target belongs to, animation curves for
that target will be ignored during evaluation.
The canonical use case for masks is to support characters holding
objects. Typically, character animations will contain hand animations in
the case that the character's hand is empty. (For example, running
animations may close a character's fingers into a fist.) However, when
the character is holding an object, the animation must be altered so
that the hand grips the object.
Bevy currently has no convenient way to handle this. The only workaround
that I can see is to have entirely separate animation clips for
characters' hands and bodies and keep them in sync, which is burdensome
and doesn't match artists' expectations from other engines, which all
effectively have support for masks. However, with mask group support,
this task is simple. We assign each hand to a mask group and parent all
character animations to a node. When a character grasps an object in
hand, we position the fingers as appropriate and then enable the mask
group for that hand in that node. This allows the character's animations
to run normally, while the object remains correctly attached to the
hand.
Note that even with this PR, we won't have support for running separate
animations for a character's hand and the rest of the character. This is
because we're missing additive blending: there's no way to combine the
two masked animations together properly. I intend that to be a follow-up
PR.
The major engines all have support for masks, though the workflow varies
from engine to engine:
* Unity has support for masks [essentially as implemented here], though
with layers instead of a tree. However, when using the Mecanim
("Humanoid") feature, precise control over bones is lost in favor of
predefined muscle groups.
* Unreal has a feature named [*layered blend per bone*]. This allows for
separate blend weights for different bones, effectively achieving masks.
I believe that the combination of blend nodes and masks make Bevy's
animation graph as expressible as that of Unreal, once we have support
for additive blending, though you may have to use more nodes than you
would in Unreal. Moreover, separating out the concepts of "blend weight"
and "which bones this node applies to" seems like a cleaner design than
what Unreal has.
* Godot's `AnimationTree` has the notion of [*blend filters*], which are
essentially the same as masks as implemented in this PR.
Additionally, this patch fixes a bug with weight evaluation whereby
weights weren't properly propagated down to grandchildren, because the
weight evaluation for a node only checked its parent's weight, not its
evaluated weight. I considered submitting this as a separate PR, but
given that this PR refactors that code entirely to support masks and
weights under a unified "evaluated node" concept, I simply included the
fix here.
A new example, `animation_masks`, has been added. It demonstrates how to
toggle masks on and off for specific portions of a skin.
This is part of #14395, but I'm going to defer closing that issue until
we have additive blending.
[essentially as implemented here]:
https://docs.unity3d.com/560/Documentation/Manual/class-AvatarMask.html
[*layered blend per bone*]:
https://dev.epicgames.com/documentation/en-us/unreal-engine/using-layered-animations-in-unreal-engine
[*blend filters*]:
https://docs.godotengine.org/en/stable/tutorials/animation/animation_tree.html
## Migration Guide
* The serialized format of animation graphs has changed with the
addition of animation masks. To upgrade animation graph RON files, add
`mask` and `mask_groups` fields as appropriate. (They can be safely set
to zero.)
# Objective
`bevy_animation` imports a lot of items - and it uses a very
inconsistent code style to do so.
## Solution
Changes the offending `use` statements to be more consistent across the
crate.
## Testing
- Did you test these changes? If so, how?
- No testing is needed beyond lint checks, and those finished
successfully.
- ~~Are there any parts that need more testing?~~
- ~~How can other people (reviewers) test your changes? Is there
anything specific they need to know?~~
- ~~If relevant, what platforms did you test these changes on, and are
there any important ones you can't test?~~
# Objective
Add a convenience constructor to make simple animation graphs easier to
build.
I've had some notes about attempting this since #11989 that I just
remembered after seeing #14852.
This partially addresses #14852, but I don't really know animation well
enough to write all of the documentation it's asking for.
## Solution
Add `AnimationGraph::from_clips` and use it to simplify `animated_fox`.
Do some other little bits of incidental cleanup and documentation .
## Testing
I ran `cargo run --example animated_fox`.
# Objective
Fixes#14782
## Solution
Enable the lint and fix all upcoming hints (`--fix`). Also tried to
figure out the false-positive (see review comment). Maybe split this PR
up into multiple parts where only the last one enables the lint, so some
can already be merged resulting in less many files touched / less
potential for merge conflicts?
Currently, there are some cases where it might be easier to read the
code with the qualifier, so perhaps remove the import of it and adapt
its cases? In the current stage it's just a plain adoption of the
suggestions in order to have a base to discuss.
## Testing
`cargo clippy` and `cargo run -p ci` are happy.
# Objective
The `AssetReader` trait allows customizing the behavior of fetching
bytes for an `AssetPath`, and expects implementors to return `dyn
AsyncRead + AsyncSeek`. This gives implementors of `AssetLoader` great
flexibility to tightly integrate their asset loading behavior with the
asynchronous task system.
However, almost all implementors of `AssetLoader` don't use the async
functionality at all, and just call `AsyncReadExt::read_to_end(&mut
Vec<u8>)`. This is incredibly inefficient, as this method repeatedly
calls `poll_read` on the trait object, filling the vector 32 bytes at a
time. At my work we have assets that are hundreds of megabytes which
makes this a meaningful overhead.
## Solution
Turn the `Reader` type alias into an actual trait, with a provided
method `read_to_end`. This provided method should be more efficient than
the existing extension method, as the compiler will know the underlying
type of `Reader` when generating this function, which removes the
repeated dynamic dispatches and allows the compiler to make further
optimizations after inlining. Individual implementors are able to
override the provided implementation -- for simple asset readers that
just copy bytes from one buffer to another, this allows removing a large
amount of overhead from the provided implementation.
Now that `Reader` is an actual trait, I also improved the ergonomics for
implementing `AssetReader`. Currently, implementors are expected to box
their reader and return it as a trait object, which adds unnecessary
boilerplate to implementations. This PR changes that trait method to
return a pseudo trait alias, which allows implementors to return `impl
Reader` instead of `Box<dyn Reader>`. Now, the boilerplate for boxing
occurs in `ErasedAssetReader`.
## Testing
I made identical changes to my company's fork of bevy. Our app, which
makes heavy use of `read_to_end` for asset loading, still worked
properly after this. I am not aware if we have a more systematic way of
testing asset loading for correctness.
---
## Migration Guide
The trait method `bevy_asset::io::AssetReader::read` (and `read_meta`)
now return an opaque type instead of a boxed trait object. Implementors
of these methods should change the type signatures appropriately
```rust
impl AssetReader for MyReader {
// Before
async fn read<'a>(&'a self, path: &'a Path) -> Result<Box<Reader<'a>>, AssetReaderError> {
let reader = // construct a reader
Box::new(reader) as Box<Reader<'a>>
}
// After
async fn read<'a>(&'a self, path: &'a Path) -> Result<impl Reader + 'a, AssetReaderError> {
// create a reader
}
}
```
`bevy::asset::io::Reader` is now a trait, rather than a type alias for a
trait object. Implementors of `AssetLoader::load` will need to adjust
the method signature accordingly
```rust
impl AssetLoader for MyLoader {
async fn load<'a>(
&'a self,
// Before:
reader: &'a mut bevy::asset::io::Reader,
// After:
reader: &'a mut dyn bevy::asset::io::Reader,
_: &'a Self::Settings,
load_context: &'a mut LoadContext<'_>,
) -> Result<Self::Asset, Self::Error> {
}
```
Additionally, implementors of `AssetReader` that return a type
implementing `futures_io::AsyncRead` and `AsyncSeek` might need to
explicitly implement `bevy::asset::io::Reader` for that type.
```rust
impl bevy::asset::io::Reader for MyAsyncReadAndSeek {}
```
# Objective
Simplify implementing some asset traits without Box::pin(async move{})
shenanigans.
Fixes (in part) https://github.com/bevyengine/bevy/issues/11308
## Solution
Use async-fn in traits when possible in all traits. Traits with return
position impl trait are not object safe however, and as AssetReader and
AssetWriter are both used with dynamic dispatch, you need a Boxed
version of these futures anyway.
In the future, Rust is [adding
](https://blog.rust-lang.org/2023/12/21/async-fn-rpit-in-traits.html)proc
macros to generate these traits automatically, and at some point in the
future dyn traits should 'just work'. Until then.... this seemed liked
the right approach given more ErasedXXX already exist, but, no clue if
there's plans here! Especially since these are public now, it's a bit of
an unfortunate API, and means this is a breaking change.
In theory this saves some performance when these traits are used with
static dispatch, but, seems like most code paths go through dynamic
dispatch, which boxes anyway.
I also suspect a bunch of the lifetime annotations on these function
could be simplified now as the BoxedFuture was often the only thing
returned which needed a lifetime annotation, but I'm not touching that
for now as traits + lifetimes can be so tricky.
This is a revival of
[pull/11362](https://github.com/bevyengine/bevy/pull/11362) after a
spectacular merge f*ckup, with updates to the latest Bevy. Just to recap
some discussion:
- Overall this seems like a win for code quality, especially when
implementing these traits, but a loss for having to deal with ErasedXXX
variants.
- `ConditionalSend` was the preferred name for the trait that might be
Send, to deal with wasm platforms.
- When reviewing be sure to disable whitespace difference, as that's 95%
of the PR.
## Changelog
- AssetReader, AssetWriter, AssetLoader, AssetSaver and Process now use
async-fn in traits rather than boxed futures.
## Migration Guide
- Custom implementations of AssetReader, AssetWriter, AssetLoader,
AssetSaver and Process should switch to async fn rather than returning a
bevy_utils::BoxedFuture.
- Simultaniously, to use dynamic dispatch on these traits you should
instead use dyn ErasedXXX.
This is an implementation of RFC #51:
https://github.com/bevyengine/rfcs/blob/main/rfcs/51-animation-composition.md
Note that the implementation strategy is different from the one outlined
in that RFC, because two-phase animation has now landed.
# Objective
Bevy needs animation blending. The RFC for this is [RFC 51].
## Solution
This is an implementation of the RFC. Note that the implementation
strategy is different from the one outlined there, because two-phase
animation has now landed.
This is just a draft to get the conversation started. Currently we're
missing a few things:
- [x] A fully-fleshed-out mechanism for transitions
- [x] A serialization format for `AnimationGraph`s
- [x] Examples are broken, other than `animated_fox`
- [x] Documentation
---
## Changelog
### Added
* The `AnimationPlayer` has been reworked to support blending multiple
animations together through an `AnimationGraph`, and as such will no
longer function unless a `Handle<AnimationGraph>` has been added to the
entity containing the player. See [RFC 51] for more details.
* Transition functionality has moved from the `AnimationPlayer` to a new
component, `AnimationTransitions`, which works in tandem with the
`AnimationGraph`.
## Migration Guide
* `AnimationPlayer`s can no longer play animations by themselves and
need to be paired with a `Handle<AnimationGraph>`. Code that was using
`AnimationPlayer` to play animations will need to create an
`AnimationGraph` asset first, add a node for the clip (or clips) you
want to play, and then supply the index of that node to the
`AnimationPlayer`'s `play` method.
* The `AnimationPlayer::play_with_transition()` method has been removed
and replaced with the `AnimationTransitions` component. If you were
previously using `AnimationPlayer::play_with_transition()`, add all
animations that you were playing to the `AnimationGraph`, and create an
`AnimationTransitions` component to manage the blending between them.
[RFC 51]:
https://github.com/bevyengine/rfcs/blob/main/rfcs/51-animation-composition.md
---------
Co-authored-by: Rob Parrett <robparrett@gmail.com>
