# Objective
We recently got some neat new 2d shapes and the shapes are no longer
centered on the screen.
The hardcoded positions and colors are a pain to deal with when a new
shape is added.
## Solution
Delete a bunch of code and position shapes evenly. Assign colors evenly
too.
## Before
<img width="1280" alt="Screenshot 2024-02-14 at 3 17 40 PM"
src="https://github.com/bevyengine/bevy/assets/200550/cc9fd9a8-4019-4907-a50e-621cb656c20a">
## After
<img width="1280" alt="Screenshot 2024-02-14 at 3 17 24 PM"
src="https://github.com/bevyengine/bevy/assets/200550/033a3f91-d3bc-4ec8-af59-42a221f8b8e7">
---------
Co-authored-by: BD103 <59022059+BD103@users.noreply.github.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Joona Aalto <jondolf.dev@gmail.com>
# Objective
The first part of #10569, split up from #11007.
The goal is to implement meshing support for Bevy's new geometric
primitives, starting with 2D primitives. 3D meshing will be added in a
follow-up, and we can consider removing the old mesh shapes completely.
## Solution
Add a `Meshable` trait that primitives need to implement to support
meshing, as suggested by the
[RFC](https://github.com/bevyengine/rfcs/blob/main/rfcs/12-primitive-shapes.md#meshing).
```rust
/// A trait for shapes that can be turned into a [`Mesh`].
pub trait Meshable {
/// The output of [`Self::mesh`]. This can either be a [`Mesh`]
/// or a builder used for creating a [`Mesh`].
type Output;
/// Creates a [`Mesh`] for a shape.
fn mesh(&self) -> Self::Output;
}
```
This PR implements it for the following primitives:
- `Circle`
- `Ellipse`
- `Rectangle`
- `RegularPolygon`
- `Triangle2d`
The `mesh` method typically returns a builder-like struct such as
`CircleMeshBuilder`. This is needed to support shape-specific
configuration for things like mesh resolution or UV configuration:
```rust
meshes.add(Circle { radius: 0.5 }.mesh().resolution(64));
```
Note that if no configuration is needed, you can even skip calling
`mesh` because `From<MyPrimitive>` is implemented for `Mesh`:
```rust
meshes.add(Circle { radius: 0.5 });
```
I also updated the `2d_shapes` example to use primitives, and tweaked
the colors to have better contrast against the dark background.
Before:
After:
Here you can see the UVs and different facing directions: (taken from
#11007, so excuse the 3D primitives at the bottom left)
---
## Changelog
- Added `bevy_render::mesh::primitives` module
- Added `Meshable` trait and implemented it for:
- `Circle`
- `Ellipse`
- `Rectangle`
- `RegularPolygon`
- `Triangle2d`
- Implemented `Default` and `Copy` for several 2D primitives
- Updated `2d_shapes` example to use primitives
- Tweaked colors in `2d_shapes` example to have better contrast against
the (new-ish) dark background
---------
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Motivation
When spawning entities into a scene, it is very common to create assets
like meshes and materials and to add them via asset handles. A common
setup might look like this:
```rust
fn setup(
mut commands: Commands,
mut meshes: ResMut<Assets<Mesh>>,
mut materials: ResMut<Assets<StandardMaterial>>,
) {
commands.spawn(PbrBundle {
mesh: meshes.add(Mesh::from(shape::Cube { size: 1.0 })),
material: materials.add(StandardMaterial::from(Color::RED)),
..default()
});
}
```
Let's take a closer look at the part that adds the assets using `add`.
```rust
mesh: meshes.add(Mesh::from(shape::Cube { size: 1.0 })),
material: materials.add(StandardMaterial::from(Color::RED)),
```
Here, "mesh" and "material" are both repeated three times. It's very
explicit, but I find it to be a bit verbose. In addition to being more
code to read and write, the extra characters can sometimes also lead to
the code being formatted to span multiple lines even though the core
task, adding e.g. a primitive mesh, is extremely simple.
A way to address this is by using `.into()`:
```rust
mesh: meshes.add(shape::Cube { size: 1.0 }.into()),
material: materials.add(Color::RED.into()),
```
This is fine, but from the names and the type of `meshes`, we already
know what the type should be. It's very clear that `Cube` should be
turned into a `Mesh` because of the context it's used in. `.into()` is
just seven characters, but it's so common that it quickly adds up and
gets annoying.
It would be nice if you could skip all of the conversion and let Bevy
handle it for you:
```rust
mesh: meshes.add(shape::Cube { size: 1.0 }),
material: materials.add(Color::RED),
```
# Objective
Make adding assets more ergonomic by making `Assets::add` take an `impl
Into<A>` instead of `A`.
## Solution
`Assets::add` now takes an `impl Into<A>` instead of `A`, so e.g. this
works:
```rust
commands.spawn(PbrBundle {
mesh: meshes.add(shape::Cube { size: 1.0 }),
material: materials.add(Color::RED),
..default()
});
```
I also changed all examples to use this API, which increases consistency
as well because `Mesh::from` and `into` were being used arbitrarily even
in the same file. This also gets rid of some lines of code because
formatting is nicer.
---
## Changelog
- `Assets::add` now takes an `impl Into<A>` instead of `A`
- Examples don't use `T::from(K)` or `K.into()` when adding assets
## Migration Guide
Some `into` calls that worked previously might now be broken because of
the new trait bounds. You need to either remove `into` or perform the
conversion explicitly with `from`:
```rust
// Doesn't compile
let mesh_handle = meshes.add(shape::Cube { size: 1.0 }.into()),
// These compile
let mesh_handle = meshes.add(shape::Cube { size: 1.0 }),
let mesh_handle = meshes.add(Mesh::from(shape::Cube { size: 1.0 })),
```
## Concerns
I believe the primary concerns might be:
1. Is this too implicit?
2. Does this increase codegen bloat?
Previously, the two APIs were using `into` or `from`, and now it's
"nothing" or `from`. You could argue that `into` is slightly more
explicit than "nothing" in cases like the earlier examples where a
`Color` gets converted to e.g. a `StandardMaterial`, but I personally
don't think `into` adds much value even in this case, and you could
still see the actual type from the asset type.
As for codegen bloat, I doubt it adds that much, but I'm not very
familiar with the details of codegen. I personally value the user-facing
code reduction and ergonomics improvements that these changes would
provide, but it might be worth checking the other effects in more
detail.
Another slight concern is migration pain; apps might have a ton of
`into` calls that would need to be removed, and it did take me a while
to do so for Bevy itself (maybe around 20-40 minutes). However, I think
the fact that there *are* so many `into` calls just highlights that the
API could be made nicer, and I'd gladly migrate my own projects for it.
# Objective
I was about to submit a PR to add these two examples to `bevy-website` and re-discovered the inconsistency.
Although it's not a major issue on the website where only the filenames are shown, this would help to visually distinguish the two examples in the list because the names are very prominent.
This also helps out when fuzzy-searching the codebase for these files.
## Solution
Rename `shapes` to `2d_shapes`. Now the filename matches the example name, and the naming structure matches the 3d example.
## Notes
@Nilirad proposed this in https://github.com/bevyengine/bevy/pull/4613#discussion_r862455631 but it had slipped away from my brain at that time.
