`Atmosphere` is now an entity

Previously, the Atmosphere component was added to the camera. In 0.19, the Atmosphere is spawned as an entity. The nearest atmosphere will be chosen for rendering.

AtmosphereSettings still belongs to the camera. This is the component that enables atmosphere rendering for that view.

The scene_units_to_m field has been removed from AtmosphereSettings. Use Transform on the Atmosphere entity for scale. It is inversely proportional to the old scene_units_to_m factor. For example, to treat one unit as 1 km (as with scene_units_to_m: 1000.0), set scale to 0.001.

// 0.18
commands.spawn((
    Camera3d::default(),
    Atmosphere::earth(earth_medium),
    AtmosphereSettings {
        scene_units_to_m: 1000.0,
        ..default()
    },
));

// 0.19
let earth = Atmosphere::earth(earth_medium);
let scale = 0.001;
commands.spawn((
    earth,
    Transform::from_scale(Vec3::splat(scale)).with_translation(-Vec3::Y * earth.inner_radius * scale),
));

commands.spawn((
    Camera3d::default(),
    AtmosphereSettings::default(),
));

If you don't need to customize the scale, a default Transform component is added that positions the atmosphere such that the horizon lines up with the camera's default Y-up direction.

commands.spawn(Atmosphere::earth(earth_medium));

The bottom_radius and top_radius fields on the Atmosphere component have been renamed to inner_radius and outer_radius respectively to reflect their new meaning.

See the updated atmosphere example and documentation for details.

There have been some renames:

• Atmosphere::earthlike -> Atmosphere::earth
• bevy::pbr::Atmosphere -> bevy::light::Atmosphere
• bevy::pbr::ScatteringMedium -> bevy::light::atmosphere::ScatteringMedium