I'm new to writing games. I'm planning to write a 2D battle game which may require an physics engine. Suppose I've written one, but how can I combine it with the main routine of my game? Should I attach it directly to the graphics render routine or put it in an individual thread? I've spent much time looking for some common approach, but found nothing. So can you reveal some basics idea for me, a newbie? Thanks!

P.S. There're many other problems I have to deal with if I choose to start a separate thread for the physics engine, for example, the lock problem, while from my intuition, I guess I'd better separate the render and the physics engine.