games/examples/parallax.rs

use games::*;

fn main() {
    App::new()
        .add_plugins((BaseGamePlugin {
            name: "parallax example".into(),
            title: "Parallax".into(),
            game_type: GameType::Two,
        },))
        .add_systems(Startup, spawn_background)
        .add_systems(Update, move_camera)
        .add_systems(Update, parallax_gizmos)
        .add_systems(Update, wrap_parallax_items.run_if(any_component_changed::<ViewVisibility>))
        .run();
}

fn spawn_background(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<ColorMaterial>>,
) {
    let mesh = Mesh2d(meshes.add(Circle::new(1.0)));
    commands.spawn((
        Name::new("Depth: 1"),
        Transform::default().with_scale(Vec3::splat(50.0)),
        mesh.clone(),
        MeshMaterial2d(materials.add(ColorMaterial::from_color(RED))),
        ParallaxDepth(1.0),
        Visibility::Inherited,
        children![(Text2d("1.0".into()), Transform::from_xyz(0.0, 35.0, 0.0))],
    ));
    commands.spawn((
        Name::new("Depth: 2"),
        Transform::default().with_scale(Vec3::splat(50.0)),
        mesh.clone(),
        MeshMaterial2d(materials.add(ColorMaterial::from_color(GREEN))),
        ParallaxDepth(2.0),
        Visibility::Inherited,
        children![(Text2d("2.0".into()), Transform::from_xyz(0.0, 35.0, 0.0))],
    ));
    commands.spawn((
        Name::new("Depth: 4"),
        Transform::default().with_scale(Vec3::splat(50.0)),
        mesh.clone(),
        MeshMaterial2d(materials.add(ColorMaterial::from_color(BLUE))),
        ParallaxDepth(4.0),
        Visibility::Inherited,
        children![(Text2d("4.0".into()), Transform::from_xyz(0.0, 35.0, 0.0))],
    ));
    commands.spawn((
        Name::new("Depth: 8"),
        Transform::default().with_scale(Vec3::splat(50.0)),
        mesh.clone(),
        MeshMaterial2d(materials.add(ColorMaterial::from_color(YELLOW))),
        ParallaxDepth(8.0),
        Visibility::Inherited,
        children![(Text2d("8.0".into()), Transform::from_xyz(0.0, 35.0, 0.0))],
    ));
}

fn move_camera(mut t: Single<&mut Transform, With<Camera2d>>, keys: Res<ButtonInput<KeyCode>>) {
    if keys.pressed(KeyCode::ArrowLeft) {
        t.translation.x -= 5.0;
    } else if keys.pressed(KeyCode::ArrowRight) {
        t.translation.x += 5.0;
    }

    if keys.pressed(KeyCode::ArrowDown) {
        t.translation.y -= 5.0;
    } else if keys.pressed(KeyCode::ArrowUp) {
        t.translation.y += 5.0;
    }
}

fn parallax_gizmos(mut gizmos: Gizmos, q: Query<&Transform, With<ParallaxDepth>>) {
    // Closest to camera
    // Parallax(1)
    q.iter().for_each(|t| {
        gizmos
            .grid_2d(
                t.translation.truncate(),
                UVec2::new(5, 5),
                Vec2::splat(10.),
                MAGENTA,
            )
            .outer_edges();
    });
}

fn wrap_parallax_items(
    mut items: Query<(&mut Transform, &GlobalTransform, &ViewVisibility), (With<ParallaxDepth>, Without<Camera2d>, Changed<ViewVisibility>)>,
    camera: Single<(&Camera, &GlobalTransform), With<Camera2d>>,
    window: Single<&Window>,
) {
    if !items.is_empty() {
        let (cam, cam_gt) = *camera;

        // get the window size in world space
        let window_size_in_world_space = {
            let top_left = cam.viewport_to_world_2d(cam_gt, Vec2::ZERO).unwrap();
            let bottom_right = cam.viewport_to_world_2d(cam_gt, window.size()).unwrap();

            Vec2::abs(Vec2::new(bottom_right.x - top_left.x, bottom_right.y - top_left.y))
        };
        info!("Window size: {:?}", window_size_in_world_space);

        // for each item in the paralax items
        items.iter_mut().for_each(|(mut t, gt, v)| {
            if !v.get() {
                info!("The item is not visible");

                // Get the total size (window + scale)
                let total_size = window_size_in_world_space + (t.scale.truncate() * 2.0);
                info!("Window size: {:?} | Object size: {:?}", window_size_in_world_space, t.scale.truncate());
                info!("Total size: {:?}", total_size);

                // Double check that item is out of bounds
                let bounds_check = Vec2::abs(cam_gt.translation().truncate() - gt.translation().truncate());
                let out_of_bounds = (total_size / 2.0) - bounds_check;
                info!("Bounds check {:?}", bounds_check);
                info!("Out of bounds: {:?}", out_of_bounds);
                info!("Starting position: {:?}", t.translation);
                if out_of_bounds.x < 0.0 {
                    info!("Object is actually out of bounds horizontally");
                    // determine if should move to the left or right relative to camera
                    let move_right = cam_gt.translation().x > gt.translation().x;

                    // move left or right
                    if move_right {
                        t.translation.x += total_size.x;
                    } else {
                        t.translation.x -= total_size.x;
                    }
                }
                if out_of_bounds.y < 0.0 {
                    info!("Object is actually out of bounds vertically");
                    let move_up = cam_gt.translation().y > gt.translation().y;

                    // move up or down
                    if move_up {
                        t.translation.y += total_size.y;
                    } else {
                        t.translation.y -= total_size.y;
                    }
                }
                info!("Moved to {:?}", t.translation);
            }
        });
    }
}