Query and modify mesh

[open raven]

Hi here !
I created a mesh, like this:

fn example(
    mut commands: Commands,
    meshes: &mut ResMut<Assets<Mesh>>,
    materials: &mut ResMut<Assets<ColorMaterial>>,
) {
    commands.spawn(
        (
            ProgressDone,
            MaterialMesh2dBundle {
                mesh: meshes.add(Mesh::from(shape::Quad::new(Vec2::ZERO))).into(),
                transform: Transform {
                    translation: Vec3::ZERO,
                    ..Default::default()
                },
                material: materials.add(ColorMaterial::from(Color::GREEN)),
                ..default()
            },
        )
    );
}

I don't know how I should Query that to be able to modify the shape. For example, from shape::Quad::new(Vec2::ZERO)) to shape::Quad::new(Vec2::new(100., 10.)))

How should I write my query to be able to do that ?

[winter bough]

@open raven If you just want to do scaling then you should modify the scale field of the Transform component.
If you want to edit or replace a mesh on an entity you can query the Handle<Mesh> component, and then get either replace it with a different handle, or get the actual mesh through Res<Assets<Mesh>> and modify it, but it's more tedious and has some drawbacks

[open raven]

goo point ! I will focus on scale !

[red mountain]

@winter bough How would you associate the mesh with an entity? I am assuming the Handle<Mesh> is a resource.

[winter bough]

@red mountain Handle<Mesh> is a component, it is associated with an entity when you spawn it with a bundle containing it (which is the case for MaterialMesh2dBundle, or PbrBundle, a bundle is just a way to add multiple components to an entity, it would add all the components of the fields of the bundle), you can also add it to an entity directly.
Assets<Mesh> is a resource. With meshes: ResMut<Assets<Mesh>> and a mesh: Mesh you can get a mesh handle with let mesh_handle = meshes.add(mesh), and get a mesh back with let mesh = meshes.get(mesh_handle).unwrap()

See for example: https://docs.rs/bevy/latest/bevy/pbr/type.PbrBundle.html#structfield.mesh

[red mountain]

I thought handle mesh was a resource?

[winter bough]

No it's a component?

You can also store it in a resource if you want/need

But that would be a resource you make yourself

Assets<Mesh> is a resource that may be where the confusion is? @red mountain

[south fjord]

Thanks, that was actually helpful! But what is the good way to store this kind of data? E.g., if I want to be able to toggle between two different materials. Oh, and is it possible to modify only one of entity's material fields without touching others?

[winter bough]

I would store those two material handles in a resource, or a component on this entity?
I'm not sure what you mean by the second question, if you change a field of the material, it will trigger a change for the whole material, which has to be sent to the rendering word again (I think, I'm actually not really sure how that goes)

[radiant steeple]

A mesh's data is stored in the resource asset<mesh>. A handle<mesh> is a component that stores the data about how to retrieve the mesh data from the resource.

In most cases if you want to change the mesh you can just create a new mesh and replace the handle such that it points to the new mesh, althought it is possible to edit the data in the existing mesh