android - 基于旋转的 Sprite 运动

Question

我在 Android OpenGL 中有一个 Sprite 。这个 Sprite (一只小甲虫)总是向前移动，我使用:

sprite.setPosition(posX, posY);

现在我有一个旋转方法，当用户向左或向右打手势时，错误会旋转:

private void applyRotation() {
    for(int i=0;i<beetleBug.size;i++) {
         Sprite s = beetleBug.get(i);
         s.setOrigin(s.getWidth() / 2, s.getHeight() / 2);
         s.setRotation(angle);
     }
}

现在，当 bug 向前移动时，他总是这样做，必须计算新的 x 和 y 坐标，这取决于旋转角度，以便 bug 总是向前移动。有没有人有通过旋转角度计算方向的算法？

这是整个 Bug 类:

public class Bug {

    private SpriteBatch             spriteBatch = null;
    private TextureAtlas            spriteSheet;
    private Array<Sprite>           beetleBug;
    private int                     currentFrame = 0;
    private final float             frameLength = 0.10f;    //in seconds, how long a frame last
    private float                   animationElapsed = 0.0f;
    private float                   angle = 0.0f;
    private float                   posX = 0.0f;
    private float                   posY = 0.0f;
    private float                   sizeX = 100.0f;
    private float                   sizeY = 100.0f;
    private float                   offSet = 50.0f;

    public Bug() {
        spriteBatch = new SpriteBatch();
        spriteSheet = new TextureAtlas("assets/data/bug.txt");
        beetleBug = spriteSheet.createSprites("bug");

        // dont forget to set the size of your sprites!
        for(int i=0; i<beetleBug.size; i++){
            beetleBug.get(i).setSize(sizeX, sizeY);

        }

        applyPosition();
    }



    public void handleInput() {

        boolean leftKey = Gdx.input.isKeyPressed(Input.Keys.LEFT);
        boolean rightKey = Gdx.input.isKeyPressed(Input.Keys.RIGHT);

        if(rightKey) {
            if(angle <= 0) {
                angle = 360;
            }
            angle -= 2f;
            applyRotation();
        }

        if(leftKey) {
            if(angle >= 360) {
                angle = 0;
            }
            angle += 2f;
            applyRotation();
        }


        applyPosition();
    }


    private void applyPosition() {
        float x = (float) Math.cos(angle);
        float y = (float) Math.sin(angle);

        posX = posX + x;
        posY = posY + y;

        for(int i=0; i<beetleBug.size; i++){
            beetleBug.get(i).setPosition(posX - offSet, posY -offSet); // optional: center the sprite to screen
        }   
    }


    private void applyRotation() {
        for(int i=0;i<beetleBug.size;i++) {
             Sprite s = beetleBug.get(i);
             s.setOrigin(s.getWidth() / 2, s.getHeight() / 2);
             s.setRotation(angle);
         }
    }

    public void render(OrthographicCamera cam) {

        float dt = Gdx.graphics.getDeltaTime();
        animationElapsed += dt;
        while(animationElapsed > frameLength){
            animationElapsed -= frameLength;
            currentFrame = (currentFrame == beetleBug.size - 1) ? 0 : ++currentFrame;
        }

        spriteBatch.setProjectionMatrix(cam.combined);

        spriteBatch.begin();
        beetleBug.get(currentFrame).draw(spriteBatch);

        spriteBatch.end();
    }
}

Answer 1

现在完美运行:

1. 将度数转换为弧度

2. 将 x 坐标设置为 -

   私有(private)无效 applyPosition() {

   float radians =  (float) Math.toRadians(angle);
   float x = -(float) Math.sin(radians);
   float y = (float) Math.cos(radians);
   
   posX = posX + x;
   posY = posY + y;
   
   for(int i=0; i<beetleBug.size; i++){
       beetleBug.get(i).setPosition(posX - offSet, posY -offSet); 
   }