Intended way to animate colors of an entity

[M3gaFr3ak]

Hello bevy community,

I wish to render a few Items that have a color changing frame-by-frame (color animations). For this, I spawn components in my setup system:

fn init(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
    asset_server: Res<AssetServer>,
) {
    let led_mat = materials.add(StandardMaterial {
        base_color: Color::rgba_linear(1.0, 1.0, 1.0, 0.95),
        emissive: if rng.gen() {
            Color::rgb_linear(rng.gen(), rng.gen(), rng.gen()) * 10.0
        } else {
            Color::BLACK
        },
        alpha_mode: AlphaMode::Add,
        ..default()
    });

    commands.spawn((
        PbrBundle {
            mesh: led_mesh.clone(),
            material: { led_mat_handle.clone() },
            transform: Transform::from_translation(Vec3::new(
                x as f32, y as f32, z as f32,
            ))
            .with_scale(Vec3::new(0.2, 0.2, 0.2)),
            ..Default::default()
        },
        AnimationState {
            progress: 0.0, // Initialize the animation progress
            y: y,
        },
        LED { index: (x, y, z) },
    ));
}

To change the color of the LED, I use an update system:

fn animate_system(
    time: Res<Time>,
    mut commands: Commands,
    mut materials: ResMut<Assets<StandardMaterial>>,
    mut query: Query<(
        &mut Transform,
        &mut AnimationState,
        &mut Handle<StandardMaterial>,
    )>,
) {
    let sinewave = 1.0 + (time.elapsed_seconds_wrapped() * 2.0 * PI * 1.0 / 4.0).sin();

    for (mut transform, mut animation_state, mut material_handle) in query.iter_mut() {
        // Update the animation state
        animation_state.progress += time.delta_seconds();

        // Apply the animation to the transform
        // This is a placeholder for your actual animation logic
        transform.translation.y =
            animation_state.y as f32 + animation_state.progress.mul(1.0).sin();

        let _material = materials.get_mut(material_handle.clone()).unwrap();
        material.emissive = Color::rgb(sinewave, sinewave, sinewave).into();
    }
}

My framerate drops from 200 fps to 16 and below, as soon as the update system is added. I traced this back to the materials.get_mut call (I guess it crosses threads?). Am I doing this the wrong way and is there an intended way to do what I want to achieve correctly?

[M3gaFr3ak]

Apart form the fps degredation, I also notice that my memory use jumps frm 160MB to 260MB according to task manager. Might this actually be a bug and linked to #2439?

Tracy show that a lot of time (160ms) is spent in pevy_pbr::materials::prepare_materials()

[M3gaFr3ak]

So I found a solution that worked for me:

Create an Image with as many pixels as entities there shall be. Create one material with the image's handle used as the emissive or base-color texture. UV map the mesh of every single entity to one pixel in the image.
In the update method I write new data into the image-data array. For this change to be applied, the Material must be updated. So to access the image, the most straight-forward way is to get_mut() the Material and use the relevant texture-member. The get_mut() triggers a material update (only one, not 4096 as in my original approach).