Question

I have an image which moves horizontally with a given speed over a delta time(dt). But the problem is,the image doesn’t bounces off when it reaches the end of the size of the world.How can i make the image bounces off backward so it would be kept inside the world?

Any help will do.

Here’s what i’ve tried so far:

@Override
public void move(long dt)
{
    // v = dx / dt
    //   dx m = v m/s  . dt s

    double dt_s = dt / 1e9;
    double dx_m = speed * dt_s;


    double left_wall = 0;
    double right_wall = board.x1_world;

    if (x <= right_wall)
    {
        x += dx_m;
        if (x >= right_wall)
        {

            x = right_wall;
           x *= -dx_m;
        }
    }
}

Answer 1

    @Override
public void move(long dt)
{
    double dt_s = dt / 1e9;
    double dx_m = speed * dt_s;


    double left_wall = 0;
    double right_wall = board.x1_world;

    x += dx_m;
    if (x <= 0) speed *= -1.0;
    if (x >= right_wall) speed *= -1.0;
}

When the x coordinate of your images reach an border, just change the orientation of the horizontal speed (multiply it for -1). But you should use an condition like this:

if (x >= (right_wall - width_of_image)) speed *= -1.0;

Instead of just x >= right_wall, because doing so, the image will bounce when it “touchs” the end of the world.