I HAVE FOUND A SOLUTION. I think.
AMD Phenom Black 9950 X4
SLI GTX 260 x 2
6gb DDR2 1066
SSD (OCZ Vertex 2)
Sharp Aquos 52" - 1920x1080
Relevant in-game settings:
Everything maxed except Shadows at Medium
V Sync ON
Frame limit at 60
I have been tracking down this issue since launch. Studying it. Trying to get a feel of it. Tried countless setting adjustments and stuff, including SLI related ones.
It haunted me endlessly and definitely gobbled up hours of gameplay just trying to narrow it down.
But I had pretty much given up hope by now.
Until I came back in the spider cave during my first Hell run.
The stuttering was just unbelievable, made the level very painful and frustrating to play in.
So again, I started toying around with settings and stuff. And then I noticed something.
If I walked a few steps up and down at one specific place (still in spider cave), thus bringing some environment stuff on and off screen, the FPS would go from 60 to 30. Yep that clean a cut. not 28, not 31. 30.
One spot stable at 60. Walk down 2 steps, stabilizes down at 30.
I was like, wtf, what's going on with these mushrooms that makes my FPS go down a whopping 30 FPS just by having them on screen?
So to the narrow down process. First thing I tried was bringing down (in-game settings) Anti-Aliasing, Clutter, Physics, in that order, one value at a time. No change. Still 30 FPS.
Then Shadows. Downed to Low, no Change. And then...
Shadows OFF. BOOM. FPS kicks back to 60.
Put Shadows to Low again... wham, FPS down to 30. Shadows to off again, and it kicks back to 60.
So there you go. On my specific setup, shadows are the issue.
My conclusion is that certain environmental decoration assets can be affected by shadows so much that it can make FPS jump from 60 to 30 in an instant.
So that 's bound to create stuttering wouldn't you think so? It means that this stuff going off and on screen when you move around makes your FPS alternate between 60 and 30 repeatedly and very fast, creating stuttering.
That being said... seriously? I have to turn shadows OFF to play the game flawlessly? I mean I don't have the most kick !@# rig but it's definitely not bad, in most games I played maxed out WITH shadows, sometimes at a lower setting like Medium since I don'T mind the minimal difference in quality, but NEVER before did I have to turn them completely OFF.
As a QA Lead for X game company, I am fairly certain that this is a fixable engine issue. It's just not normal to see that big of a difference between off and low by staying in the exact same spot with nothing going on except for slowly dangling mushrooms. I have seen and reported similar issues in other games, which usually were fixed by the engine departement in a matter of days.
Submitting a ticket with this info, already taken a screenshot of the spot, so hopefully this helps Blizz track this down and fix it :)