Commit Graph

16 Commits

Author SHA1 Message Date
Lynn
450a9202d0
Common MeshBuilder trait (#13411)
# Objective

- All `ShapeMeshBuilder`s have some methods/implementations in common.
These are `fn build(&self) -> Mesh` and this implementation:
```rust
impl From<ShapeMeshBuilder> for Mesh { 
    fn from(builder: ShapeMeshBuilder) -> { 
        builder.build() 
    } 
}
``` 

- For the sake of consistency, these can be moved into a shared trait

## Solution

- Add `trait MeshBuilder` containing a `fn build(&self) -> Mesh` and
implementing `MeshBuilder for ShapeMeshBuilder`
- Implement `From<T: MeshBuilder> for Mesh`

## Migration Guide

- When calling `.build()` you need to import
`bevy_render::mesh::primitives::MeshBuilder`
2024-05-18 11:58:11 +00:00
Joona Aalto
ac1f135e20
Add meshing for Cone (#11820)
# Objective

The `Cone` primitive should support meshing.

## Solution

Implement meshing for the `Cone` primitive. The default cone has a
height of 1 and a base radius of 0.5, and is centered at the origin.

An issue with cone meshes is that the tip does not really have a normal
that works, even with duplicated vertices. This PR uses only a single
vertex for the tip, with a normal of zero; this results in an "invalid"
normal that gets ignored by the fragment shader. This seems to be the
only approach we have for perfectly smooth cones. For discussion on the
topic, see #10298 and #5891.

Another thing to note is that the cone uses polar coordinates for the
UVs:

<img
src="https://github.com/bevyengine/bevy/assets/57632562/e101ded9-110a-4ac4-a98d-f1e4d740a24a"
alt="cone" width="400" />

This way, textures are applied as if looking at the cone from above:

<img
src="https://github.com/bevyengine/bevy/assets/57632562/8dea00f1-a283-4bc4-9676-91e8d4adb07a"
alt="texture" width="200" />

<img
src="https://github.com/bevyengine/bevy/assets/57632562/d9d1b5e6-a8ba-4690-b599-904dd85777a1"
alt="cone" width="200" />
2024-05-13 18:00:59 +00:00
andristarr
2b3e3341d6
separating finite and infinite 3d planes (#12426)
# Objective

Fixes #12388

## Solution

- Removing the plane3d and adding rect3d primitive mesh
2024-04-18 14:13:22 +00:00
Matty
956604e4c7
Meshing for Triangle3d primitive (#12686)
# Objective

- Ongoing work for #10572 
- Implement the `Meshable` trait for `Triangle3d`, allowing 3d triangle
primitives to produce meshes.

## Solution

The `Meshable` trait for `Triangle3d` directly produces a `Mesh`, much
like that of `Triangle2d`. The mesh consists only of a single triangle
(the triangle itself), and its vertex data consists of:
- Vertex positions, which are the triangle's vertices themselves (i.e.
the triangle provides its own coordinates in mesh space directly)
- Normals, which are all the normal of the triangle itself
- Indices, which are directly inferred from the vertex order (note that
this is slightly different than `Triangle2d` which, because of its lower
dimension, has an orientation which can be corrected for so that it
always faces "the right way")
- UV coordinates, which are produced as follows:
1. The first coordinate is coincident with the `ab` direction of the
triangle.
2. The second coordinate maps to be perpendicular to the first in mesh
space, so that the UV-mapping is skew-free.
3. The UV-coordinates map to the smallest rectangle possible containing
the triangle, given the preceding constraints.

Here is a visual demonstration; here, the `ab` direction of the triangle
is horizontal, left to right — the point `c` moves, expanding the
bounding rectangle of the triangle when it pushes past `a` or `b`:

<img width="1440" alt="Screenshot 2024-03-23 at 5 36 01 PM"
src="https://github.com/bevyengine/bevy/assets/2975848/bef4d786-7b82-4207-abd4-ac4557d0f8b8">

<img width="1440" alt="Screenshot 2024-03-23 at 5 38 12 PM"
src="https://github.com/bevyengine/bevy/assets/2975848/c0f72b8f-8e70-46fa-a750-2041ba6dfb78">

<img width="1440" alt="Screenshot 2024-03-23 at 5 37 15 PM"
src="https://github.com/bevyengine/bevy/assets/2975848/db287e4f-2b0b-4fd4-8d71-88f4e7a03b7c">

The UV-mapping of `Triangle2d` has also been changed to use the same
logic.

---

## Changelog

- Implemented `Meshable` for `Triangle3d`.
- Changed UV-mapping of `Triangle2d` to match that of `Triangle3d`.

## Migration Guide

The UV-mapping of `Triangle2d` has changed with this PR; the main
difference is that the UVs are no longer dependent on the triangle's
absolute coordinates, but instead follow translations of the triangle
itself in its definition. If you depended on the old UV-coordinates for
`Triangle2d`, then you will have to update affected areas to use the new
ones which, briefly, can be described as follows:
- The first coordinate is parallel to the line between the first two
vertices of the triangle.
- The second coordinate is orthogonal to this, pointing in the direction
of the third point.

Generally speaking, this means that the first two points will have
coordinates `[_, 0.]`, while the third coordinate will be `[_, 1.]`,
with the exact values depending on the position of the third point
relative to the first two. For acute triangles, the first two vertices
always have UV-coordinates `[0., 0.]` and `[1., 0.]` respectively. For
obtuse triangles, the third point will have coordinate `[0., 1.]` or
`[1., 1.]`, with the coordinate of one of the two other points shifting
to maintain proportionality.

For example: 
- The default `Triangle2d` has UV-coordinates `[0., 0.]`, `[0., 1.]`,
[`0.5, 1.]`.
- The triangle with vertices `vec2(0., 0.)`, `vec2(1., 0.)`, `vec2(2.,
1.)` has UV-coordinates `[0., 0.]`, `[0.5, 0.]`, `[1., 1.]`.
- The triangle with vertices `vec2(0., 0.)`, `vec2(1., 0.)`, `vec2(-2.,
1.)` has UV-coordinates `[2./3., 0.]`, `[1., 0.]`, `[0., 1.]`.

## Discussion

### Design considerations

1. There are a number of ways to UV-map a triangle (at least two of
which are fairly natural); for instance, we could instead declare the
second axis to be essentially `bc` so that the vertices are always `[0.,
0.]`, `[0., 1.]`, and `[1., 0.]`. I chose this method instead because it
is skew-free, so that the sampling from textures has only bilinear
scaling. I think this is better for cases where a relatively "uniform"
texture is mapped to the triangle, but it's possible that we might want
to support the other thing in the future. Thankfully, we already have
the capability of easily expanding to do that with Builders if the need
arises. This could also allow us to provide things like barycentric
subdivision.
2. Presently, the mesh-creation code for `Triangle3d` is set up to never
fail, even in the case that the triangle is degenerate. I have mixed
feelings about this, but none of our other primitive meshes fail, so I
decided to take the same approach. Maybe this is something that could be
worth revisiting in the future across the board.

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Jakub Marcowski <37378746+Chubercik@users.noreply.github.com>
2024-04-08 23:00:04 +00:00
Matty
c8aa3ac7d1
Meshing for Annulus primitive (#12734)
# Objective

Related to #10572 
Allow the `Annulus` primitive to be meshed.

## Solution

We introduce a `Meshable` structure, `AnnulusMeshBuilder`, which allows
the `Annulus` primitive to be meshed, leaving optional configuration of
the number of angular sudivisions to the user. Here is a picture of the
annulus's UV-mapping:
<img width="1440" alt="Screenshot 2024-03-26 at 10 39 48 AM"
src="https://github.com/bevyengine/bevy/assets/2975848/b170291d-cba7-441b-90ee-2ad6841eaedb">

Other features are essentially identical to the implementations for
`Circle`/`Ellipse`.

---

## Changelog

- Introduced `AnnulusMeshBuilder`
- Implemented `Meshable` for `Annulus` with `Output =
AnnulusMeshBuilder`
- Implemented `From<Annulus>` and `From<AnnulusMeshBuilder>` for `Mesh`
- Added `impl_reflect!` declaration for `Annulus` and `Triangle3d` in
`bevy_reflect`

---

## Discussion

### Design considerations

The only interesting wrinkle here is that the existing UV-mapping of
`Ellipse` (and hence of `Circle` and `RegularPolygon`) is non-radial
(it's skew-free, created by situating the mesh in a bounding rectangle),
so the UV-mapping of `Annulus` doesn't limit to that of `Circle` as its
inner radius tends to zero, for instance. I don't see this as a real
issue for `Annulus`, which should almost certainly have this kind of
UV-mapping, but I think we ought to at least consider allowing mesh
configuration for `Circle`/`Ellipse` that performs radial UV-mapping
instead. (In these cases in particular, it would be especially easy,
since we wouldn't need a different parameter set in the builder.)

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2024-04-01 21:55:49 +00:00
Emi
16fb995697
change doc for SphereKind::Ico to reflect that the triangles are equa… (#12482)
# Objective
Fixes #12480 
by removing the explicit mention of equally sized triangles from the doc
for icospheres

Co-authored-by: Emi <emanuel.boehm@gmail.com>
2024-03-15 03:32:52 +00:00
Joona Aalto
f418de8eb6
Rename Direction2d/3d to Dir2/3 (#12189)
# Objective

Split up from #12017, rename Bevy's direction types.

Currently, Bevy has the `Direction2d`, `Direction3d`, and `Direction3dA`
types, which provide a type-level guarantee that their contained vectors
remain normalized. They can be very useful for a lot of APIs for safety,
explicitness, and in some cases performance, as they can sometimes avoid
unnecessary normalizations.

However, many consider them to be inconvenient to use, and opt for
standard vector types like `Vec3` because of this. One reason is that
the direction type names are a bit long and can be annoying to write (of
course you can use autocomplete, but just typing `Vec3` is still nicer),
and in some intances, the extra characters can make formatting worse.
The naming is also inconsistent with Glam's shorter type names, and
results in names like `Direction3dA`, which (in my opinion) are
difficult to read and even a bit ugly.

This PR proposes renaming the types to `Dir2`, `Dir3`, and `Dir3A`.
These names are nice and easy to write, consistent with Glam, and work
well for variants like the SIMD aligned `Dir3A`. As a bonus, it can also
result in nicer formatting in a lot of cases, which can be seen from the
diff of this PR.

Some examples of what it looks like: (copied from #12017)

```rust
// Before
let ray_cast = RayCast2d::new(Vec2::ZERO, Direction2d::X, 5.0);

// After
let ray_cast = RayCast2d::new(Vec2::ZERO, Dir2::X, 5.0);
```

```rust
// Before (an example using Bevy XPBD)
let hit = spatial_query.cast_ray(
    Vec3::ZERO,
    Direction3d::X,
    f32::MAX,
    true,
    SpatialQueryFilter::default(),
);

// After
let hit = spatial_query.cast_ray(
    Vec3::ZERO,
    Dir3::X,
    f32::MAX,
    true,
    SpatialQueryFilter::default(),
);
```

```rust
// Before
self.circle(
    Vec3::new(0.0, -2.0, 0.0),
    Direction3d::Y,
    5.0,
    Color::TURQUOISE,
);

// After (formatting is collapsed in this case)
self.circle(Vec3::new(0.0, -2.0, 0.0), Dir3::Y, 5.0, Color::TURQUOISE);
```

## Solution

Rename `Direction2d`, `Direction3d`, and `Direction3dA` to `Dir2`,
`Dir3`, and `Dir3A`.

---

## Migration Guide

The `Direction2d` and `Direction3d` types have been renamed to `Dir2`
and `Dir3`.

## Additional Context

This has been brought up on the Discord a few times, and we had a small
[poll](https://discord.com/channels/691052431525675048/1203087353850364004/1212465038711984158)
on this. `Dir2`/`Dir3`/`Dir3A` was quite unanimously chosen as the best
option, but of course it was a very small poll and inconclusive, so
other opinions are certainly welcome too.

---------

Co-authored-by: IceSentry <c.giguere42@gmail.com>
2024-02-28 22:48:43 +00:00
Joona Aalto
9bd6cc0a5e
Add Direction3dA and move direction types out of primitives (#12018)
# Objective

Split up from #12017, add an aligned version of `Direction3d` for SIMD,
and move direction types out of `primitives`.

## Solution

Add `Direction3dA` and move direction types into a new `direction`
module.

---

## Migration Guide

The `Direction2d`, `Direction3d`, and `InvalidDirectionError` types have
been moved out of `bevy::math::primitives`.

Before:

```rust
use bevy::math::primitives::Direction3d;
```

After:

```rust
use bevy::math::Direction3d;
```

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2024-02-26 13:57:49 +00:00
Aztro
eef7dbefe8
Add single-f32 constructors for a few (very few) primitives (#11934)
# Objective

- I hated having to do `Cuboid::new(1.0, 1.0, 1.0)` or
`Cuboid::from_size(Vec3::splat(1.0))` when there should be a much easier
way to do this.

## Solution

- Implemented a `from_length()` method that only takes in a single
float, and constructs a primitive of equal size in all directions.
- Ex:
  ```rs
  // These:
  Cuboid::new(1.0, 1.0, 1.0);
  Cuboid::from_size(Vec3::splat(1.0));
  // Are equivalent to this:
  Cuboid::from_length(1.0);
  ```
 - For the rest of the changed primitives:
    ```rs
    Rectangle::from_length(1.0);
    Plane3d::default().mesh().from_length(1.0);
    ```
2024-02-18 07:43:45 +00:00
Joona Aalto
0166db33f7
Deprecate shapes in bevy_render::mesh::shape (#11773)
# Objective

#11431 and #11688 implemented meshing support for Bevy's new geometric
primitives. The next step is to deprecate the shapes in
`bevy_render::mesh::shape` and to later remove them completely for 0.14.

## Solution

Deprecate the shapes and reduce code duplication by utilizing the
primitive meshing API for the old shapes where possible.

Note that some shapes have behavior that can't be exactly reproduced
with the new primitives yet:

- `Box` is more of an AABB with min/max extents
- `Plane` supports a subdivision count
- `Quad` has a `flipped` property

These types have not been changed to utilize the new primitives yet.

---

## Changelog

- Deprecated all shapes in `bevy_render::mesh::shape`
- Changed all examples to use new primitives for meshing

## Migration Guide

Bevy has previously used rendering-specific types like `UVSphere` and
`Quad` for primitive mesh shapes. These have now been deprecated to use
the geometric primitives newly introduced in version 0.13.

Some examples:

```rust
let before = meshes.add(shape::Box::new(5.0, 0.15, 5.0));
let after = meshes.add(Cuboid::new(5.0, 0.15, 5.0));

let before = meshes.add(shape::Quad::default());
let after = meshes.add(Rectangle::default());

let before = meshes.add(shape::Plane::from_size(5.0));
// The surface normal can now also be specified when using `new`
let after = meshes.add(Plane3d::default().mesh().size(5.0, 5.0));

let before = meshes.add(
    Mesh::try_from(shape::Icosphere {
        radius: 0.5,
        subdivisions: 5,
    })
    .unwrap(),
);
let after = meshes.add(Sphere::new(0.5).mesh().ico(5).unwrap());
```
2024-02-08 18:01:34 +00:00
Lynn
4c86ad6aed
Mesh insert indices (#11745)
# Objective

- Fixes #11740 

## Solution

- Turned `Mesh::set_indices` into `Mesh::insert_indices` and added
related methods for completeness.

---

## Changelog

- Replaced `Mesh::set_indices(indices: Option<Indices>)` with
`Mesh::insert_indices(indices: Indices)`
- Replaced `Mesh::with_indices(indices: Option<Indices>)` with
`Mesh::with_inserted_indices(indices: Indices)` and
`Mesh::with_removed_indices()` mirroring the API for inserting /
removing attributes.
- Updated the examples and internal uses of the APIs described above.

## Migration Guide

- Use `Mesh::insert_indices` or `Mesh::with_inserted_indices` instead of
`Mesh::set_indices` / `Mesh::with_indices`.
- If you have passed `None` to `Mesh::set_indices` or
`Mesh::with_indices` you should use `Mesh::remove_indices` or
`Mesh::with_removed_indices` instead.

---------

Co-authored-by: François <mockersf@gmail.com>
2024-02-06 23:31:48 +00:00
Joona Aalto
cf15e6bba3
Implement Meshable for some 3D primitives (#11688)
# Objective

Split up from #11007, fixing most of the remaining work for #10569.

Implement `Meshable` for `Cuboid`, `Sphere`, `Cylinder`, `Capsule`,
`Torus`, and `Plane3d`. This covers all shapes that Bevy has mesh
structs for in `bevy_render::mesh::shapes`.

`Cone` and `ConicalFrustum` are new shapes, so I can add them in a
follow-up, or I could just add them here directly if that's preferrable.

## Solution

Implement `Meshable` for `Cuboid`, `Sphere`, `Cylinder`, `Capsule`,
`Torus`, and `Plane3d`.

The logic is mostly just a copy of the the existing `bevy_render`
shapes, but `Plane3d` has a configurable surface normal that affects the
orientation. Some property names have also been changed to be more
consistent.

The default values differ from the old shapes to make them a bit more
logical:

- Spheres now have a radius of 0.5 instead of 1.0. The default capsule
is equivalent to the default cylinder with the sphere's halves glued on.
- The inner and outer radius of the torus are now 0.5 and 1.0 instead of
0.5 and 1.5 (i.e. the new minor and major radii are 0.25 and 0.75). It's
double the width of the default cuboid, half of its height, and the
default sphere matches the size of the hole.
- `Cuboid` is 1x1x1 by default unlike the dreaded `Box` which is 2x1x1.

Before, with "old" shapes:


![old](https://github.com/bevyengine/bevy/assets/57632562/733f3dda-258c-4491-8152-9829e056a1a3)

Now, with primitive meshing:


![new](https://github.com/bevyengine/bevy/assets/57632562/5a1af14f-bb98-401d-82cf-de8072fea4ec)

I only changed the `3d_shapes` example to use primitives for now. I can
change them all in this PR or a follow-up though, whichever way is
preferrable.

### Sphere API

Spheres have had separate `Icosphere` and `UVSphere` structs, but with
primitives we only have one `Sphere`.

We need to handle this with builders:

```rust
// Existing structs
let ico = Mesh::try_from(Icophere::default()).unwrap();
let uv = Mesh::from(UVSphere::default());

// Primitives
let ico = Sphere::default().mesh().ico(5).unwrap();
let uv = Sphere::default().mesh().uv(32, 18);
```

We could add methods on `Sphere` directly to skip calling `.mesh()`.

I also added a `SphereKind` enum that can be used with the `kind`
method:

```rust
let ico = Sphere::default()
    .mesh()
    .kind(SphereKind::Ico { subdivisions: 8 })
    .build();
```

The default mesh for a `Sphere` is an icosphere with 5 subdivisions
(like the default `Icosphere`).

---

## Changelog

- Implement `Meshable` and `Default` for `Cuboid`, `Sphere`, `Cylinder`,
`Capsule`, `Torus`, and `Plane3d`
- Use primitives in `3d_shapes` example

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2024-02-06 21:44:13 +00:00
Tristan Guichaoua
694c06f3d0
Inverse missing_docs logic (#11676)
# Objective

Currently the `missing_docs` lint is allowed-by-default and enabled at
crate level when their documentations is complete (see #3492).
This PR proposes to inverse this logic by making `missing_docs`
warn-by-default and mark crates with imcomplete docs allowed.

## Solution

Makes `missing_docs` warn at workspace level and allowed at crate level
when the docs is imcomplete.
2024-02-03 21:40:55 +00:00
Joona Aalto
9bad607df9
Implement meshing for Capsule2d (#11639)
# Objective

The `Capsule2d` primitive was added in #11585. It should support meshing
like the other 2D primitives.

## Solution

Implement meshing for `Capsule2d`.

It doesn't currently support "rings" like Bevy's `Capsule` shape (not
`Capsule3d`), but it does support resolution to control the number of
vertices used for one hemicircle. The total vertex count is two times
the resolution; if we allowed setting the full vertex count, odd numbers
would lead to uneven vertex counts for the top and bottom hemicircles
and produce potentially unwanted results.

The capsule looks like this (with UV visualization and wireframe) using
resolutions of 16, 8, and 3:

![Resolution
16](https://github.com/bevyengine/bevy/assets/57632562/feae22de-bdc5-438a-861f-848284b67a52)
![Resolution
8](https://github.com/bevyengine/bevy/assets/57632562/e95aab8e-793f-45ac-8a74-8be39f7626dd)
![Resolution of
3](https://github.com/bevyengine/bevy/assets/57632562/bcf01d23-1d8b-4cdb-966a-c9022a07c287)

The `2d_shapes` example now includes the capsule, so we also get one
more color of the rainbow 🌈

![New 2D shapes
example](https://github.com/bevyengine/bevy/assets/57632562/1c45b5f5-d26a-4e8c-8e8a-e106ab14d46e)
2024-02-03 18:03:43 +00:00
Brian Reavis
6b40b6749e
RenderAssetPersistencePolicy → RenderAssetUsages (#11399)
# Objective

Right now, all assets in the main world get extracted and prepared in
the render world (if the asset's using the RenderAssetPlugin). This is
unfortunate for two cases:

1. **TextureAtlas** / **FontAtlas**: This one's huge. The individual
`Image` assets that make up the atlas are cloned and prepared
individually when there's no reason for them to be. The atlas textures
are built on the CPU in the main world. *There can be hundreds of images
that get prepared for rendering only not to be used.*
2. If one loads an Image and needs to transform it in a system before
rendering it, kind of like the [decompression
example](https://github.com/bevyengine/bevy/blob/main/examples/asset/asset_decompression.rs#L120),
there's a price paid for extracting & preparing the asset that's not
intended to be rendered yet.

------

* References #10520
* References #1782

## Solution

This changes the `RenderAssetPersistencePolicy` enum to bitflags. I felt
that the objective with the parameter is so similar in nature to wgpu's
[`TextureUsages`](https://docs.rs/wgpu/latest/wgpu/struct.TextureUsages.html)
and
[`BufferUsages`](https://docs.rs/wgpu/latest/wgpu/struct.BufferUsages.html),
that it may as well be just like that.

```rust
// This asset only needs to be in the main world. Don't extract and prepare it.
RenderAssetUsages::MAIN_WORLD

// Keep this asset in the main world and  
RenderAssetUsages::MAIN_WORLD | RenderAssetUsages::RENDER_WORLD

// This asset is only needed in the render world. Remove it from the asset server once extracted.
RenderAssetUsages::RENDER_WORLD
```

### Alternate Solution

I considered introducing a third field to `RenderAssetPersistencePolicy`
enum:
```rust
enum RenderAssetPersistencePolicy {
    /// Keep the asset in the main world after extracting to the render world.
    Keep,
    /// Remove the asset from the main world after extracting to the render world.
    Unload,
    /// This doesn't need to be in the render world at all.
    NoExtract, // <-----
}
```
Functional, but this seemed like shoehorning. Another option is renaming
the enum to something like:
```rust
enum RenderAssetExtractionPolicy {
    /// Extract the asset and keep it in the main world.
    Extract,
    /// Remove the asset from the main world after extracting to the render world.
    ExtractAndUnload,
    /// This doesn't need to be in the render world at all.
    NoExtract,
}
```
I think this last one could be a good option if the bitflags are too
clunky.

## Migration Guide

* `RenderAssetPersistencePolicy::Keep` → `RenderAssetUsage::MAIN_WORLD |
RenderAssetUsage::RENDER_WORLD` (or `RenderAssetUsage::default()`)
* `RenderAssetPersistencePolicy::Unload` →
`RenderAssetUsage::RENDER_WORLD`
* For types implementing the `RenderAsset` trait, change `fn
persistence_policy(&self) -> RenderAssetPersistencePolicy` to `fn
asset_usage(&self) -> RenderAssetUsages`.
* Change any references to `cpu_persistent_access`
(`RenderAssetPersistencePolicy`) to `asset_usage` (`RenderAssetUsage`).
This applies to `Image`, `Mesh`, and a few other types.
2024-01-30 13:22:10 +00:00
Joona Aalto
2bf481c03b
Add Meshable trait and implement meshing for 2D primitives (#11431)
# 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:

![Old 2D
shapes](https://github.com/bevyengine/bevy/assets/57632562/f1d8c2d5-55be-495f-8ed4-5890154b81ca)

After:

![New 2D
shapes](https://github.com/bevyengine/bevy/assets/57632562/f166c013-34b8-4752-800a-5517b284d978)

Here you can see the UVs and different facing directions: (taken from
#11007, so excuse the 3D primitives at the bottom left)

![UVs and facing
directions](https://github.com/bevyengine/bevy/assets/57632562/eaf0be4e-187d-4b6d-8fb8-c996ba295a8a)

---

## 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>
2024-01-29 16:47:47 +00:00