Not really surprised. Their method of ropes is... strange. Its definitely realistic, but as a result murders FPS.
CE3 seems to handle ropes from a base-up approach. Firstly, the ropes are made up of segments. You could really call it a "chain", just made to look like a rope. When you pull on the bottom segment, it pulls on the next, which in turn pulls on the next, etc. Unfortunately, All this pulling is updated on a frame-per-frame basis*, which is just really, really demanding on the CPU. In the end, you do get a very realistic rope-like setup. It's really pretty good. However, they could have lowered the realism a bit, and gone with a 2-point spline system, which would just rely on a passive-update system. It wouldn't look as good, or be as realistic when interacting with it, but for that application, it would be identical. The other issue murdering FPS here is that there's an object at the end of the rope. Now you've got a physics check on it, as well as the rope. Every frame the engine goes "hey this is pulling down on segment 1", and then segment one says to segment 2 "im being pulled on, and I'm also pulling on you". It adds up.
*Its frame-by-frame when IN-FRAME. Physics simulations of single objects (cloth, ropes, etc.) pause when off-camera to increase performance. Its quite hard to tell, but there IS a console command to disable this feature (enjoy 20fps EVERYWHERE in the 1st level), and you can test for this via shadows. If a light is shining on a tarp or something and casting a shadow, keep the tarp behind you, and the shadow in front of you. Once the tarp is off-frame, the shadow will stop moving, as the object casting it has stopped moving.
Edited by doomlord52 - 2/25/13 at 11:05am