将光标转换为世界坐标

[点击这里下载完整示例代码][cbexample::cursor2worldy]

Bevy 还没有提供内置的功能来帮助找出光标当前所指向的东西。

3D 游戏

这是一个很好的（非官方）插件： bevy_mod_picking.

2D 游戏

下面是一个简单的取巧解决方案，用于使用默认的 Bevy 2d 摄像机正射投影的游戏：

/// Used to help identify our main camera
#[derive(Component)]
struct MainCamera;

fn setup(mut commands: Commands) {
    commands.spawn()
        .insert_bundle(OrthographicCameraBundle::new_2d())
        .insert(MainCamera);
}

fn my_cursor_system(
    // need to get window dimensions
    wnds: Res<Windows>,
    // query to get camera transform
    q_camera: Query<&Transform, With<MainCamera>>
) {
    // get the primary window
    let wnd = wnds.get_primary().unwrap();

    // check if the cursor is in the primary window
    if let Some(pos) = wnd.cursor_position() {
        // get the size of the window
        let size = Vec2::new(wnd.width() as f32, wnd.height() as f32);

        // the default orthographic projection is in pixels from the center;
        // just undo the translation
        let p = pos - size / 2.0;

        // assuming there is exactly one main camera entity, so this is OK
        let camera_transform = q_camera.single();

        // apply the camera transform
        let pos_wld = camera_transform.compute_matrix() * p.extend(0.0).extend(1.0);
        eprintln!("World coords: {}/{}", pos_wld.x, pos_wld.y);
    }
}