# 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
70f7d9598a