# Objective

It can sometimes be useful to transform actual `Mesh` data without
needing to change the `Transform` of an entity. For example, one might
want to spawn a circle mesh facing up instead of facing Z, or to spawn a
mesh slightly offset without needing child entities.

## Solution

Add `transform_by` and `transformed_by` methods to `Mesh`. They take a
`Transform` and apply the translation, rotation, and scale to vertex
positions, and the rotation to normals and tangents.

In the `load_gltf` example, with this system:

```rust
fn transform(time: Res<Time>, mut q: Query<&mut Handle<Mesh>>, mut meshes: ResMut<Assets<Mesh>>) {
    let sin = 0.0025 * time.elapsed_seconds().sin();

    for mesh_handle in &mut q {
        if let Some(mesh) = meshes.get_mut(mesh_handle.clone_weak()) {
            let transform =
                Transform::from_rotation(Quat::from_rotation_y(0.75 * time.delta_seconds()))
                    .with_scale(Vec3::splat(1.0 + sin));
            mesh.transform_by(transform);
        }
    }
}
```

it looks like this:


https://github.com/bevyengine/bevy/assets/57632562/60432456-6d28-4d06-9c94-2f4148f5acd5

# Objective

It can sometimes be useful to transform actual `Mesh` data without
needing to change the `Transform` of an entity. For example, one might
want to spawn a circle mesh facing up instead of facing Z, or to spawn a
mesh slightly offset without needing child entities.

## Solution

Add `transform_by` and `transformed_by` methods to `Mesh`. They take a
`Transform` and apply the translation, rotation, and scale to vertex
positions, and the rotation to normals and tangents.

In the `load_gltf` example, with this system:

```rust
fn transform(time: Res<Time>, mut q: Query<&mut Handle<Mesh>>, mut meshes: ResMut<Assets<Mesh>>) {
    let sin = 0.0025 * time.elapsed_seconds().sin();

    for mesh_handle in &mut q {
        if let Some(mesh) = meshes.get_mut(mesh_handle.clone_weak()) {
            let transform =
                Transform::from_rotation(Quat::from_rotation_y(0.75 * time.delta_seconds()))
                    .with_scale(Vec3::splat(1.0 + sin));
            mesh.transform_by(transform);
        }
    }
}
```

it looks like this:


https://github.com/bevyengine/bevy/assets/57632562/60432456-6d28-4d06-9c94-2f4148f5acd5

# Objective

It can sometimes be useful to combine several meshes into one. This
allows constructing more complex meshes out of simple primitives without
needing to use a 3D modeling program or entity hierarchies.

This could also be used internally to increase code reuse by using
existing mesh generation logic for e.g. circles and using that in
cylinder mesh generation logic to add the top and bottom of the
cylinder.

**Note**: This is *not* implementing CSGs (Constructive Solid Geometry)
or any boolean operations, as that is much more complex. This is simply
adding the mesh data of another mesh to a mesh.

## Solution

Add a `merge` method to `Mesh`. It appends the vertex attributes and
indices of `other` to `self`, resulting in a `Mesh` that is the
combination of the two.

For example, you could do this:

```rust
let mut cuboid = Mesh::from(shape::Box::default());
let mut cylinder = Mesh::from(shape::Cylinder::default());
let mut torus = Mesh::from(shape::Torus::default());

cuboid.merge(cylinder);
cuboid.merge(torus);
```

This would result in `cuboid` being a `Mesh` that also has the cylinder
mesh and torus mesh. In this case, they would just be placed on top of
each other, but by utilizing #11454 we can transform the cylinder and
torus to get a result like this:


https://github.com/bevyengine/bevy/assets/57632562/557402c6-b896-4aba-bd95-312e7d1b5238

This is just a single entity and a single mesh.

# Objective

Make it straightforward to translate and rotate bounding volumes.

## Solution

Add `translate_by`/`translated_by`, `rotate_by`/`rotated_by`,
`transform_by`/`transformed_by` methods to the `BoundingVolume` trait.
This follows the naming used for mesh transformations (see #11454 and
#11675).

---

## Changelog

- Added `translate_by`/`translated_by`, `rotate_by`/`rotated_by`,
`transform_by`/`transformed_by` methods to the `BoundingVolume` trait
and implemented them for the bounding volumes
- Renamed `Position` associated type to `Translation`

---------

Co-authored-by: Mateusz Wachowiak <mateusz_wachowiak@outlook.com>

# Objective

Make it straightforward to translate and rotate bounding volumes.

## Solution

Add `translate_by`/`translated_by`, `rotate_by`/`rotated_by`,
`transform_by`/`transformed_by` methods to the `BoundingVolume` trait.
This follows the naming used for mesh transformations (see bevyengine#11454 and
bevyengine#11675).

---

## Changelog

- Added `translate_by`/`translated_by`, `rotate_by`/`rotated_by`,
`transform_by`/`transformed_by` methods to the `BoundingVolume` trait
and implemented them for the bounding volumes
- Renamed `Position` associated type to `Translation`

---------

Co-authored-by: Mateusz Wachowiak <mateusz_wachowiak@outlook.com>

# Objective

Make it straightforward to translate and rotate bounding volumes.

## Solution

Add `translate_by`/`translated_by`, `rotate_by`/`rotated_by`,
`transform_by`/`transformed_by` methods to the `BoundingVolume` trait.
This follows the naming used for mesh transformations (see bevyengine#11454 and
bevyengine#11675).

---

## Changelog

- Added `translate_by`/`translated_by`, `rotate_by`/`rotated_by`,
`transform_by`/`transformed_by` methods to the `BoundingVolume` trait
and implemented them for the bounding volumes
- Renamed `Position` associated type to `Translation`

---------

Co-authored-by: Mateusz Wachowiak <mateusz_wachowiak@outlook.com>