Some fixes in scene edition, along with clipping in the engine player

Actually, I started copying your implementation, but found out this method and thought it was simpler (the less code we maintain, the best). I know it makes the operation every loop, but, at the end, are just a couple of matrix multiplications. Considering that there is already hundreds of calls to multiply matrix (during drawing and hit), I think this approach is cleaner and doesn't add any significant overload. Unless there is something else I'm not aware of that would make this approach worsen performance a lot.