Bevy Version:0.12(outdated!)

Visibility

Relevant official examples: parenting.


Visibility is used to control if something is to be rendered or not. If you want an entity to exist in the world, just not be displayed, you can hide it.

/// Prepare the game map, but do not display it until later
fn setup_map_hidden(
    mut commands: Commands,
) {
    commands.spawn((
        GameMapEntity,
        SceneBundle {
            scene: todo!(),
            visibility: Visibility::Hidden,
            ..Default::default()
        },
    ));
}

/// When everything is ready, un-hide the game map
fn reveal_map(
    mut query: Query<&mut Visibility, With<GameMapEntity>>,
) {
    let mut vis_map = query.single_mut();
    *vis_map = Visibility::Visible;
}

Visibility Components

In Bevy, visibility is represented by multiple components:

Any Entity that represents a renderable object in the game world needs to have them all. All of Bevy's built-in bundle types include them.

If you are creating a custom entity without using those bundles, you can use one of the following to ensure you don't miss them:

fn spawn_special_entity(
    mut commands: Commands,
) {
    // create an entity that does not use one of the common Bevy bundles,
    // but still needs transforms and visibility
    commands.spawn((
        ComponentA,
        ComponentB,
        SpatialBundle {
            transform: Transform::from_scale(Vec3::splat(3.0)),
            visibility: Visibility::Hidden,
            ..Default::default()
        },
    ));
}

If you don't do this correctly (say, you manually add just the Visibility component and forget the others, because you don't use a bundle), your entities will not render!

Visibility

Visibility is the "user-facing toggle". This is where you specify what you want for the current entity:

  • Inherited (default): show/hide depending on parent
  • Visible: always show the entity, regardless of parent
  • Hidden: always hide the entity, regardless of parent

If the current entity has any children that have Inherited, their visibility will be affected if you set the current entity to Visible or Hidden.

If an entity has a parent, but the parent entity is missing the visibility-related components, things will behave as if there was no parent.

InheritedVisibility

InheritedVisibility represents the state the current entity would have based on its parent's visibility.

The value of InheritedVisibility should be considered read-only. It is managed internally by Bevy, in a manner similar to transform propagation. A "visibility propagation" system runs in the PostUpdate schedule.

If you want to read the up-to-date value for the current frame, you should add your system to the PostUpdate schedule and order it after VisibilitySystems::VisibilityPropagate.

/// Check if a specific UI button is visible
/// (could be hidden if the whole menu is hidden?)
fn debug_player_visibility(
    query: Query<&InheritedVisibility, With<MyAcceptButton>>,
) {
    let vis = query.single();

    debug!("Button visibility: {:?}", vis.get());
}
use bevy::render::view::VisibilitySystems;

app.add_systems(PostUpdate,
    debug_player_visibility
        .after(VisibilitySystems::VisibilityPropagate)
);

ViewVisibility

ViewVisibility represents the actual final decision made by Bevy about whether this entity needs to be rendered.

The value of ViewVisibility is read-only. It is managed internally by Bevy.

It is used for "culling": if the entity is not in the range of any Camera or Light, it does not need to be rendered, so Bevy will hide it to improve performance.

Every frame, after "visibility propagation", Bevy will check what entities can be seen by what view (camera or light), and store the outcome in these components.

If you want to read the up-to-date value for the current frame, you should add your system to the PostUpdate schedule and order it after VisibilitySystems::CheckVisibility.

/// Check if balloons are seen by any Camera, Light, etc… (not culled)
fn debug_balloon_visibility(
    query: Query<&ViewVisibility, With<Balloon>>,
) {
    for vis in query.iter() {
        if vis.get() {
            debug!("Balloon will be rendered.");
        }
    }
}
use bevy::render::view::VisibilitySystems;

app.add_systems(PostUpdate,
    debug_balloon_visibility
        .after(VisibilitySystems::CheckVisibility)
);