The physics engine shows some strange behavior during LAN game play, such as when a player throws a grenade, causing several vehicles to explode. Now, what does a player with a PhysX card see, and what happens on computers without a physics accelerator?
Video demo5 one with
The first video shows a computer equipped with a PhysX card. We start up Ghost Recon Advanced Warfighter in LAN mode. At the starting point, we then blow up two vehicles with a grenade. The vehicles are thrown into the air and flipped over.
Video demo5 one with out insight
In the second video, the player with the PhysX hardware again throws the grenades. A second player who doesn't have a physics accelerator installed stands by and watches. No matter how many grenades are used, the vehicles will not roll over. The player with the PhysX card sees additional wreckage flying from the vehicles, which the player without the Ageia card naturally can't see.
Video demo5 without Ageia
In the third video, the player without the physics accelerator stands in the spot previously occupied by the player with the PhysX card, who in turn takes a different starting location, out of sight of his teammate. This time, the furious explosion makes a comeback and the vehicles are flipped over, even on the computer without physics acceleration.
Our video comparison shows that the physics accelerator is not required for the vehicles to flip over. As soon as a second player appears on the scene, the vehicles remain in place as if they were bolted to the ground, unperturbed by shockwaves. Possibly, the programmers wanted to avoid irregularities. After all, it would seem very strange if one player saw the wreck of a vehicle being thrown around by an explosion while his teammate didn't.
This situation really shows the weaknesses of the physics engine, as the vehicle-flipping effect would by ideally suited to hardware acceleration. However, since the vehicles are treated as solid bodies, it seems that the programmers decided to forego spectacular trajectories in favor of simpler collision-detection in multiplayer environments. Therefore, the Ageia card is limited to calculating only the flying debris and splinters, neither of which represents solid materials from the player's perspective, as mentioned above.
Another negative effect of the physics hardware in network games is that it causes events to happen asynchronously across the clients. This manifests itself as a noticeable lag when two players are within sight of each other and one has a PhysX card and the other does not. When the player with the machine that does not have the physics accelerator hears an explosion, the player with the Ageia card has not heard it yet.