# Objective
The way `Curve` presently achieves dyn-compatibility involves shoving
`Self: Sized` bounds on a bunch of methods to forbid them from appearing
in vtables. (This is called *explicit non-dispatchability*.) The `Curve`
trait probably also just has way too many methods on its own.
In the past, using extension traits instead to achieve similar
functionality has been discussed. The upshot is that this would allow
the "core" of the curve trait, on which all the automatic methods rely,
to live in a very simple dyn-compatible trait, while other functionality
is implemented by extensions. For instance, `dyn Curve<T>` cannot use
the `Sized` methods, but `Box<dyn Curve<T>>` is `Sized`, hence would
automatically implement the extension trait, containing the methods
which are currently non-dispatchable.
Other motivations for this include modularity and code organization: the
`Curve` trait itself has grown quite large with the addition of numerous
adaptors, and refactoring it to demonstrate the separation of
functionality that is already present makes a lot of sense. Furthermore,
resampling behavior in particular is dependent on special traits that
may be mimicked or analogized in user-space, and creating extension
traits to achieve similar behavior in user-space is something we ought
to encourage by example.
## Solution
`Curve` now contains only `domain` and the `sample` methods.
`CurveExt` has been created, and it contains all adaptors, along with
the other sampling convenience methods (`samples`, `sample_iter`, etc.).
It is implemented for all `C` where `C: Curve<T> + Sized`.
`CurveResampleExt` has been created, and it contains all resampling
methods. It is implemented for all `C` where `C: Curve<T> + ?Sized`.
## Testing
It compiles and `cargo doc` succeeds.
---
## Future work
- Consider writing extension traits for resampling curves in related
domains (e.g. resampling for `Curve<T>` where `T: Animatable` into an
`AnimatableKeyframeCurve`).
- `CurveExt` might be further broken down to separate the adaptor and
sampling methods.
---
## Migration Guide
`Curve` has been refactored so that much of its functionality is now in
extension traits. Adaptors such as `map`, `reparametrize`, `reverse`,
and so on now require importing `CurveExt`, while the resampling methods
`resample_*` require importing `CurveResampleExt`. Both of these new
traits are exported through `bevy::math::curve` and through
`bevy::math::prelude`.
# Objective
Add a way to use the gizmo API in a retained manner, for increased
performance.
## Solution
- Move gizmo API from `Gizmos` to `GizmoBuffer`, ~ab~using `Deref` to
keep usage the same as before.
- Merge non-strip and strip variant of `LineGizmo` into one, storing the
data in a `GizmoBuffer` to have the same API for retained `LineGizmo`s.
### Review guide
- The meat of the changes are in `lib.rs`, `retained.rs`, `gizmos.rs`,
`pipeline_3d.rs` and `pipeline_2d.rs`
- The other files contain almost exclusively the churn from moving the
gizmo API from `Gizmos` to `GizmoBuffer`
## Testing
### Performance
Performance compared to the immediate mode API is from 65 to 80 times
better for static lines.
```
7900 XTX, 3700X
1707.9k lines/ms: gizmos_retained (21.3ms)
3488.5k lines/ms: gizmos_retained_continuous_polyline (31.3ms)
0.5k lines/ms: gizmos_retained_separate (97.7ms)
3054.9k lines/ms: bevy_polyline_retained_nan (16.8ms)
3596.3k lines/ms: bevy_polyline_retained_continuous_polyline (14.2ms)
0.6k lines/ms: bevy_polyline_retained_separate (78.9ms)
26.9k lines/ms: gizmos_immediate (14.9ms)
43.8k lines/ms: gizmos_immediate_continuous_polyline (18.3ms)
```
Looks like performance is good enough, being close to par with
`bevy_polyline`.
Benchmarks can be found here:
This branch:
https://github.com/tim-blackbird/line_racing/tree/retained-gizmos
Bevy 0.14: https://github.com/DGriffin91/line_racing
## Showcase
```rust
fn setup(
mut commands: Commands,
mut gizmo_assets: ResMut<Assets<GizmoAsset>>
) {
let mut gizmo = GizmoAsset::default();
// A sphere made out of one million lines!
gizmo
.sphere(default(), 1., CRIMSON)
.resolution(1_000_000 / 3);
commands.spawn(Gizmo {
handle: gizmo_assets.add(gizmo),
..default()
});
}
```
## Follow-up work
- Port over to the retained rendering world proper
- Calculate visibility and cull `Gizmo`s
# Objective
We currently use special "floating" constructors for `EasingCurve`,
`FunctionCurve`, and `ConstantCurve` (ex: `easing_curve`). This erases
the type being created (and in general "what is happening"
structurally), for very minimal ergonomics improvements. With rare
exceptions, we prefer normal `X::new()` constructors over floating `x()`
constructors in Bevy. I don't think this use case merits special casing
here.
## Solution
Add `EasingCurve::new()`, use normal constructors everywhere, and remove
the floating constructors.
I think this should land in 0.15 in the interest of not breaking people
later.
# Objective
- Add gizmos integration for the new `Curve` things in the math lib
## Solution
- Add the following methods
- `curve_2d(curve, sample_times, color)`
- `curve_3d(curve, sample_times, color)`
- `curve_gradient_2d(curve, sample_times_with_colors)`
- `curve_gradient_3d(curve, sample_times_with_colors)`
## Testing
- I added examples of the 2D and 3D variants of the gradient curve
gizmos to the gizmos examples.
## Showcase
### 2D
```rust
let domain = Interval::EVERYWHERE;
let curve = function_curve(domain, |t| Vec2::new(t, (t / 25.0).sin() * 100.0));
let resolution = ((time.elapsed_seconds().sin() + 1.0) * 50.0) as usize;
let times_and_colors = (0..=resolution)
.map(|n| n as f32 / resolution as f32)
.map(|t| (t - 0.5) * 600.0)
.map(|t| (t, TEAL.mix(&HOT_PINK, (t + 300.0) / 600.0)));
gizmos.curve_gradient_2d(curve, times_and_colors);
```
### 3D
```rust
let domain = Interval::EVERYWHERE;
let curve = function_curve(domain, |t| {
(Vec2::from((t * 10.0).sin_cos())).extend(t - 6.0)
});
let resolution = ((time.elapsed_seconds().sin() + 1.0) * 100.0) as usize;
let times_and_colors = (0..=resolution)
.map(|n| n as f32 / resolution as f32)
.map(|t| t * 5.0)
.map(|t| (t, TEAL.mix(&HOT_PINK, t / 5.0)));
gizmos.curve_gradient_3d(curve, times_and_colors);
```
