Borderlands 2, latest and probably one of the greatest games with support for GPU accelerated PhysX effects, is a HOT topic these days.
Update: GPU PhysX in Borderlands 2 – PhysX review and comparison video
Update #2: Borderlands 2 PhysX Benchmark Roundup
Usually, extra PhysX effects are meant to be executed on compatible NVIDIA GPUs, so even if one can force his CPU to do the work, it is not very effective – massive slowdowns and fps drops during scenes with intence physics are make the games hardly enjoyable. This is valid for titles like Batman series, Alice: Madness Returns, Mafia II and others.
Said matter was a tough topic over recent years, even resulting in claims that NVIDIA “hobbles” the CPU PhysX performance by purpose, to make their GPUs look more advantageous.
However, recently we saw many reports (mostly from AMD users) that Borderlands 2 shows surprisingly good performance, while running with all PhysX effects enabled even without a NVIDIA card in the system.
Thus, we decied to perform a little investigation to answer the question – can a CPU handle all the extra PhysX effects in Borderlands 2 ?
A boss fight against “Boom and his brother Bewm” is a good candidate for PhysX testing – scene contains a lot of particles (also, particles are constantly generated over time) and some cloth objects.
Gun in our hands has explosive rounds - this produces even more particles
Testing system: i7 2600K CPU, GTX 580 GPU, 8 GB RAM, Win 7 64-bit.
In-game settings: 1680×1024, all High. 60 sec sequence was recorded with FRAPS.
First of all, Borderlands 2 is showing excellent performance while utilizing GPU for PhysX calculations – minimum framerate is above 60 even on high PhysX settings.
But most interesting, CPU execution can also provide playble framerate, despite the fact that Borderlands 2 is still using good old PhysX SDK 2.8.4. We assume that some scenes in the game, containing lots of fluids, particle effects or your co-op friends, may result in lower fps (~15-20), but still – framerate won’t crawl most of the time, like in previous games.
UPDATE [26.09]: we have recieved several commentaries, that the scene we have choosen for our previous test, while being pretty heavy on PhysX effects, is still not producing too much load for the CPU.
Thus, we decided to give it another try, but now using one of the most demanding levels of the game, as we heard – Caustic Caverns.
Crystalisks are vomiting SPH Fluids
A place near the beginning of the level presents a good opportunity for testing, as it comprises several high-poly cloth pieces, many particle effects, Crystalisks and Varkids spitting SPH liquids.
Results are averaged over the two runs for each of settings.
While GPU performance took a large hit, it still can maintain minimum framerate above 30 fps and keep average framerate at pleasant 50 fps.
CPU execution of PhysX effects, in comparison, crawls at nearly unplayable 15-20 fps level. We can now clearly say that fluid simulation is affecting the CPU performance the most.
UPDATE #2 [28.09]: final round of testing, now using PhysX benchmark, built into Borderlands 2 (will be available soon in a patch).
It is designed to extensively utilize all kind of PhysX effects during the sequence.
As you may see, numbers are located somewhere in between our two previous results – benchmark scene indeed includes some complex physics interactions, but the ones you may encounter in real game will affect your framerate in more dramatical way.
To summarize: If you are playing Borderlands 2 in Single Player mode, carefully avoiding fluid emitting weapons/enemies and staying away from certain areas of the game – you may find a CPU execution of PhysX effects sufficient. But if want really comfortable gameplay, without any compromises – presence of NVIDIA GPU is still a mandatory.
P.S. if PhysX option is grayed out on your system, you still can change the settings using "PhysXLevel" parameter in "WillowEngine.ini" file:
(\Documents\My Games\Borderlands 2\WillowGame\Config)
PhysXLevel=0 - PhysX Low
PhysXLevel=1 - PhysX Medium
PhysXLevel=2 - PhysX High
P.P.S. Hybrid PhysX configurations are also supported.