java - 相对于 x 轴运动镜像

Question

我正在尝试实现移动到单击鼠标的点。

但是我遇到了 X 轴镜像行为的问题。当我点击顶部 -> 它移动到底部，当我点击底部 -> 它移动到顶部。

这里是原始位置的例子

我点击了屏幕上有红十字的位置。

但它向下移动(如箭头所示)。

有什么问题吗？我认为这似乎与运动 vector 有关。

public class Player {

    private static final float PLAYER_CIRCLE_RADIUS = 24f;
    private static final float MOVEMENT_SPEED = 200f;
    private final Circle playerCircle;

    private Vector2 direction = new Vector2();
    private Vector2 position;
    private Vector2 velocity = new Vector2();
    private Vector2 movement = new Vector2();
    private Vector2 mouseClick = new Vector2();

    public Player(float x, float y) {
        position = new Vector2(x, y);
        playerCircle = new Circle(x, y, PLAYER_CIRCLE_RADIUS);
    }

    public void draw(ShapeRenderer shapeRenderer) {
        shapeRenderer.circle(position.x, position.y, playerCircle.radius);
    }

    public void update(float delta) {
        movement.set(velocity).scl(delta);
        if (position.dst2(mouseClick) > movement.len2()) { position.add(movement); }
        else { position.set(mouseClick); }
    }

    public void setDirection(float x, float y) {
        mouseClick.set(x, y);
        direction.set(mouseClick).sub(position).nor();
        velocity.set(direction).scl(MOVEMENT_SPEED);
    }

    public Vector2 getDirection() {
        return direction;
    }

    public Circle getPlayerCircle() {
        return playerCircle;
    }

    public Vector2 getMouseClick() {
        return mouseClick;
    }
}


public class GameScreen extends ScreenAdapter {

    private static final float WORLD_WIDTH = 640;
    private static final float WORLD_HEIGHT = 480;

    private ShapeRenderer shapeRenderer;
    private Viewport viewport;
    private Camera camera;

    private Player player;
    private Destination dest;

    @Override
    public void render(float delta) {
        clearScreen();
        update(delta);
        shapeRenderer.setProjectionMatrix(camera.projection);
        shapeRenderer.setTransformMatrix(camera.view);
        shapeRenderer.begin(ShapeRenderer.ShapeType.Line);

        dest.draw(shapeRenderer);
        player.draw(shapeRenderer);

        shapeRenderer.end();
    }

    @Override
    public void resize(int width, int height) {
        viewport.update(width, height);
    }

    @Override
    public void show() {
        camera = new OrthographicCamera();
        camera.position.set(WORLD_WIDTH / 2, WORLD_HEIGHT / 2, 0);
        viewport = new FitViewport(WORLD_WIDTH, WORLD_HEIGHT, camera);
        shapeRenderer = new ShapeRenderer();

        player = new Player(WORLD_WIDTH / 2, WORLD_HEIGHT / 2);
        dest = new Destination();

        Gdx.input.setInputProcessor(new InputAdapter() {

            @Override
            public boolean touchDown(int screenX, int screenY, int pointer, int button) {
                dest.setPosition(screenX, screenY);
                camera.unproject(new Vector3(screenX, screenY, 0));
                player.setDirection(screenX, screenY);
                return true;
            }

        });
    }

    private void clearScreen() {
        Gdx.gl.glClearColor(Color.BLACK.r, Color.BLACK.g, Color.BLACK.b, Color.BLACK.a);
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
    }

    private void update(float delta) {
        player.update(delta);
    }

}

Answer 1

您所描述的实际上是在 Y 轴上镜像的。出现此行为的原因很可能是您的绘图矩阵设置为原点位于左下角，Y 轴朝上，但 gui 的原点位于左上角，Y 轴朝上- 轴朝下。因此，当您获得鼠标位置时，您应该执行以下操作:

actualPosY = screenHeight - mousePosY

这可以有效地将您的鼠标位置转换为绘图空间。