Unreal Tournament 3
Our first stop was Epic Games' latest multiplayer shooter, one of the biggest and most recent titles to take advantage of PhysX hardware acceleration. For our testing, we broke out the Unreal Tournament 3 Extreme PhysX mod pack, which includes three maps chock-full of fancy physics effects: a special version of Heat Ray, which we benchmarked below, as well as capture-the-flag arenas Tornado and Lighthouse.

Let's start with Heat Ray. Epic featured this map in the original UT3 demo, but the PhysX-enhanced version in the mod pack adds plenty of destructible items, plus an ongoing hail-storm that bombards the environment with hundreds of little ice lumps. Explosions and plasma balls from the shock rifle send hailstones and other debris flying.

Actually, a screenshot doesn't really do the hail effect justice. We've uploaded part of an Nvidia-recorded demo that showcases it in motion:

Curious to see the impact of those shiny effects on performance, we opted to run some benchmarks. We tested first with GPU physics enabled, then with software physics only, and finally in the default version of the map without added effects. Each time, we played through five 60-second deathmatch sessions against bots and recorded frame rates using FRAPS. This method likely reflects gameplay performance better than pre-recorded timedemos, although it's not precisely repeatable. Averaging five samples ought to yield sufficiently trustworthy results, though.

These numbers say it all. Using part of the GPU to compute fancy physics effects induces a performance hit, although in this case, that hit was small enough not to seriously affect playability. The version of the map without PhysX effects did feel noticeably smoother, though. As for running the PhysX map in software mode, you can forget it—long stretches of frame rates in the single digits made that config unplayable.

We also had a stroll through the other two maps—Tornado and Lighthouse. The latter isn't particularly interesting unless you really like destructible walls and floors, but Tornado uses PhysX capabilities in a cooler and more original way.

A tornado slowly crawls through the map and sucks in just about everything in its path: debris, rocks, wall chunks, pipes, shipping crates, and even liquid from a toxic pool. Roof plates bend like sheets of paper toward the sky, while projectiles from the game's flak cannon fly up in circles if you fire into the tornado. Trying to play a CTF match in this map is an interesting experience, since the tornado creates new obstacles by repositioning large objects, and it can kill players with flying debris or by flinging them against walls. Personally, I thought seeing my freshly killed corpse swallowed up into the heavens made waiting to respawn more fun.

UT3's PhysX implementation isn't perfect, of course. We encountered a number of bugs, such as objects vibrating in place and occasionally sliding in strange patterns. Planks and stone slabs in the Lighthouse map unrealistically exploded into many pieces, kind of like giant graham crackers. That said, these maps came out before Nvidia's acquisition of Ageia, so I'm not too surprised they weren't polished to a mirror shine.