如何在libGDX中以相反的方式发射子弹

Question

I have created the function of a game that a bullet goes to the way of the crosshair with a constant speed. But I have a question: how can I make the bullet go the opposite way to the way it has been shot?

Let me explain what I am trying to do. When the bullet touches a specific material, it goes the opposite way. Like this image:

As you can see, the bullet is "bouncing" to the opposite way.

Here is my function where I am setting the linear velocity from the bullet if you need it:

public void direccion(float xx, float yy) {

        float mousex = Gdx.input.getX();
        float mousey = 0;
        if (shoot.getAngle() > 6.1 && shoot.getAngle() < 9.6) { 

            mousey = Gdx.input.getY() - 5;
        } else {
            mousey = Gdx.input.getY();
        }
        Vector3 mousePos = new Vector3(mousex, mousey, 0);
        jugador.camera.unproject(mousePos);
        float speed = 60f;
        float velx = mousePos.x - xx;
        float vely = mousePos.y - yy;
        float length = (float) Math.sqrt(velx * velx + vely * vely);
        if (length != 0) {
            velx = velx / length;
            vely = vely / length;
        }
        shoot.setLinearVelocity(velx * speed, vely * speed);

Hope you could understand my idea. Can anyone help me with this?

Answer 1

After thinking about how can i do this, I had an idea.

According to vector mathematics, the bullet can take these values ​​after it touches the material in question for the rebound ...

As you can see in the picture:

After this analysis, i have adapted to a simple code.

        vectorPart = shoot.getLinearVelocity();
        if ((vectorPart.x > 0 && vectorPart.y < 0) || (vectorPart.x > 0 && vectorPart.y > 0)
                || (vectorPart.x < 0 && vectorPart.y < 0) || (vectorPart.x < 0 && vectorPart.y > 0)) {
            vectorPart = new Vector2(vectorPart.x, vectorPart.y * -1);
        } else {
            vectorPart = new Vector2(vectorPart.x * -1, vectorPart.y * -1);
        }
        shoot.setLinearVelocity(vectorPart.x, vectorPart.y);

I evaluated the linearVelocity vector and then i modified the signs of it.

With this code and anylisis everything works fine!.