bevy/crates
Patrick Walton ca8dd06146
Impose a more sensible ordering for animation graph evaluation. (#15589)
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.

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```rust
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## 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.
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design choice is not a breaking change.

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2024-10-03 00:36:42 +00:00
..
bevy_a11y Add core and alloc over std Lints (#15281) 2024-09-27 00:59:59 +00:00
bevy_animation Impose a more sensible ordering for animation graph evaluation. (#15589) 2024-10-03 00:36:42 +00:00
bevy_app Documentation for variadics (#15387) 2024-10-02 12:48:36 +00:00
bevy_asset move ANDROID_APP to bevy_window (#15585) 2024-10-02 03:01:06 +00:00
bevy_audio Migrate audio to required components (#15573) 2024-10-01 22:43:29 +00:00
bevy_color Add core and alloc over std Lints (#15281) 2024-09-27 00:59:59 +00:00
bevy_core Add core and alloc over std Lints (#15281) 2024-09-27 00:59:59 +00:00
bevy_core_pipeline Migrate motion blur, TAA, SSAO, and SSR to required components (#15572) 2024-10-01 22:45:31 +00:00
bevy_derive move ANDROID_APP to bevy_window (#15585) 2024-10-02 03:01:06 +00:00
bevy_dev_tools Simplified ui_stack_system (#9889) 2024-09-30 18:43:57 +00:00
bevy_diagnostic Runtime required components (#15458) 2024-09-30 19:20:16 +00:00
bevy_dylib Generate links to definition in source code pages on docs.rs and dev-docs.bevyengine.org (#12965) 2024-07-29 23:10:16 +00:00
bevy_ecs Implement SystemParam::queue() method for blanket implementation of ParamSet (#15599) 2024-10-02 19:46:50 +00:00
bevy_encase_derive Update `glam to 0.29, encase` to 0.10. (#15249) 2024-09-23 19:44:02 +00:00
bevy_gilrs Implement gamepads as entities (#12770) 2024-09-27 20:07:20 +00:00
bevy_gizmos Use circle gizmos for capsule (#15602) 2024-10-02 19:47:56 +00:00
bevy_gltf Migrate scenes to required components (#15579) 2024-10-01 22:42:11 +00:00
bevy_hierarchy Add VisitEntities for generic and reflectable Entity iteration (#15425) 2024-09-30 17:32:03 +00:00
bevy_input Revert "Have EntityCommands methods consume self for easier chaining" (#15523) 2024-10-02 12:47:26 +00:00
bevy_internal Add features to switch NativeActivity and GameActivity usage (#12095) 2024-10-01 22:23:48 +00:00
bevy_log Add core and alloc over std Lints (#15281) 2024-09-27 00:59:59 +00:00
bevy_macro_utils Modify derive_label to support no_std environments (#15465) 2024-09-27 20:23:26 +00:00
bevy_math add curve utilities to create curves interpolating/easing between two values (#14788) 2024-10-02 14:29:05 +00:00
bevy_mikktspace Add no_std support to bevy_mikktspace (#15528) 2024-09-30 18:17:03 +00:00
bevy_pbr Added visibility bitmask as an alternative SSAO method (#13454) 2024-10-02 13:43:35 +00:00
bevy_picking Revert "Have EntityCommands methods consume self for easier chaining" (#15523) 2024-10-02 12:47:26 +00:00
bevy_ptr Add core and alloc over std Lints (#15281) 2024-09-27 00:59:59 +00:00
bevy_reflect Documentation for variadics (#15387) 2024-10-02 12:48:36 +00:00
bevy_remote Allow access a method handler (#15601) 2024-10-02 19:45:18 +00:00
bevy_render Revert "Have EntityCommands methods consume self for easier chaining" (#15523) 2024-10-02 12:47:26 +00:00
bevy_scene Migrate scenes to required components (#15579) 2024-10-01 22:42:11 +00:00
bevy_sprite Revert "Have EntityCommands methods consume self for easier chaining" (#15523) 2024-10-02 12:47:26 +00:00
bevy_state Add core and alloc over std Lints (#15281) 2024-09-27 00:59:59 +00:00
bevy_tasks bump async-channel to 2.3.0 (#15497) 2024-09-28 19:21:59 +00:00
bevy_text Refactor TextPipeline::update_buffer to accept an interator (#15581) 2024-10-01 23:44:59 +00:00
bevy_time Add core and alloc over std Lints (#15281) 2024-09-27 00:59:59 +00:00
bevy_transform Migrate visibility to required components (#15474) 2024-09-27 19:06:16 +00:00
bevy_ui Revert "Have EntityCommands methods consume self for easier chaining" (#15523) 2024-10-02 12:47:26 +00:00
bevy_utils Add core and alloc over std Lints (#15281) 2024-09-27 00:59:59 +00:00
bevy_window move ANDROID_APP to bevy_window (#15585) 2024-10-02 03:01:06 +00:00
bevy_winit move ANDROID_APP to bevy_window (#15585) 2024-10-02 03:01:06 +00:00