Viewport.unproject() 返回 NaN（不是数字）

Question

我正在尝试以世界单位获取触摸坐标，以便我可以使用 viewport.unproject(Vector3) 在屏幕上绘制纹理，但它返回的是 NaN。

我的视口和相机如下所示：

public class GameRenderer {

    private InvadersGame game;

    private Viewport viewport;
    private OrthographicCamera camera;
    private SpriteBatch batch;
    private Animation<TextureRegion> shipAnimation;
    private TextureRegion currentShipFrame;
    private Ship ship;
    private CameraDebug cameraDebug;
    private DebugCameraConfig debugCameraConfig;

    private TextureAtlas shipAtlas;

    private float timeElapsed;

    public GameRenderer(InvadersGame game) {
        this.game = game;
        init();
    }

    private void init() {
        camera = new OrthographicCamera();
        viewport = new FitViewport(GameConfig.WORLD_WIDTH, GameConfig.WORLD_HEIGHT, camera);
        batch = new SpriteBatch();

        shipAtlas = new TextureAtlas(Gdx.files.internal(AssetPaths.shipAnimation));
        shipAnimation = new Animation<TextureRegion>(1/10f, shipAtlas.findRegions("ship"), Animation.PlayMode.LOOP);
        ship = new Ship();
        cameraDebug = new CameraDebug();
        debugCameraConfig = new DebugCameraConfig();
    }

. . .

我有一个 GameScreen class 实现屏幕并具有 GameRenderer 的实例，因此调用 init() 方法。

这是我尝试过的：

Public class GameController

. . .

 private void updateShip() {
        ship.setPositions(renderer.getViewport().unproject(ship.getTouchPos()));
        log.debug(Float.toString(renderer.getViewport().unproject(ship.getTouchPos()).x));
    }

. . .

其中 ship.getTouchPos 返回 Gdx.input.getX() 和 y 的 Vector3。

显然，我在 GameController 中有一个 GameRenderer 实例来获取视口并使用它将触摸坐标转换为世界坐标。

log.debug output：

I/chatty: uid=10133(com.mygdx.game) GLThread 342 identical 2 lines
D/GameController: NaN
D/GameController: NaN