- Subtract the position the player concluded the swipe in with the position he started the swipe in (you already do this)
- Check the angle between that Vector2D and the (1 ,0) Vector2D. You can do this by using the DotProduct: https://answers.unrealengine.com/questions/31058/how-to-get-an-angle-between-2-vectors.html?sort=oldest
- Use this image to calculate the direction:
