Bevy camera systems

When to use

Load this when a view must render 2D or 3D. Camera, Camera2d, Camera3d, and the two_passes example are the sources for the names below. The library pin is 0.20.

ECS shape

• Components: Camera is the viewpoint (projection and render target). A Camera with no render graph errors at runtime. Camera2d enables the 2D graph and requires Camera, Projection, and Frustum. Camera3d enables the main 3D graph and requires Camera and Projection. 3D space is right-handed: X right, Y up, Z back, so forward is -Z.
• Spawn: the example uses commands.spawn((Camera3d::default(), Transform::from_xyz(...).looking_at(Vec3::ZERO, Vec3::Y))). A second camera sets Camera { order: 1, clear_color: ClearColorConfig::None, ..default() } so it draws on top without clearing.
• Query: systems may take (&Camera, &GlobalTransform) with With<Camera2d>. Camera::viewport_to_world_2d maps a viewport position to a 2D world position for an orthographic camera along Z.
• Schedule: spawn on Startup. Follow, split viewports, and trauma offset are your components on Update.

fn spawn_cameras(mut commands: Commands) {
    commands.spawn((
        Camera3d::default(),
        Transform::from_xyz(0.0, 6.0, 10.0).looking_at(Vec3::ZERO, Vec3::Y),
    ));
    commands.spawn((
        Camera2d,
        Camera {
            order: 1,
            clear_color: ClearColorConfig::None,
            ..default()
        },
    ));
}

#[derive(Component)]
struct FollowTarget;

#[derive(Component)]
struct FollowCam {
    offset: Vec3,
    stiffness: f32,
}