Working Principles and Possible Limitations

Before we find out how AGEIA PhysX actually works, let’s make sure that we understand what type of tasks this solution is designed for. There are two types of physics in today’s computer games:

• Gameplay physics: physical activity of the player or the game that can affect the course of events in the virtual world. Of course, gameplay physics implies that some special physical effects are calculated on the fly, although the end result should be pre-programmed by the game developer.
• Physical effects, such as fire, water, smoke, particles, clothing, hair, etc. namely the things that only add up visual realism to the game and do not affect the gaming scenario in any way.

The physics accelerator deals only with the visual effects. Until the game developers decide to increase the physical interactivity of the game on their end or add up some innovative features such as gravity gun in Half-Life 2, for instance, any physics accelerator will only be able to slightly improve the visual effects.

PhysX physics processor can handle objects of three types:

• Rigid body objects. Here I have to say that rigid body objects, the way AGEIA and game developers perceive them, may not necessarily be simple objects. They may be pretty complex and even have moving joints. In other words, almost any model in the game may be forced to abide by physics laws. Although it is still unclear how well can we implement the objects deformation as a result of interaction with rigid body objects.
• Fluids. These serve to emulate realistic fluids behavior (such as water, blood, etc.) as well as the behavior of such substances as smoke, gas, dust, etc.
• Smart particles. These can be used to emulate the behavior of sparks, scattered glass fragments, etc.

Unlike the existing software physics implementation in the today’s games, all objects calculated by PhysX PPU can interact with one another and the surrounding environment. Moreover, there are different sets of parameters for different types of objects, including weight, density, friction, etc. According to AGEIA Technologies, all this should help game developers to achieve unbelievable gaming realism in their products.

Of course, no technology, especially the recently announced one, is absolutely flawless. Therefore, I suggest that we devote some time to discuss the possible weak spots of the current implementation of the Gaming Power Triangle concept. Looks like there could be at least three potential bottlenecks that may limit the performance of the system equipped with a new PPU:

• The first one is connected with the fluids. Although the behavior of these objects is calculated and modeled by the new PhysX, the GPU is still the one in charge of their visual representation: the parameters calculated by the PPU are transmitted to the corresponding shader. This way, if the developer gets carried away by too many fluid objects in the game, the performance of the GPU’s pixel processors may turn into a possible bottleneck of the system. However, we will not blame the AGEIA accelerator in this case, of course. Adding up more powerful graphics subsystem or performing corresponding optimizations of the gaming engine or drivers may eliminate this bottleneck.
• The second case is directly connected with the hardware peculiarities of AGEIA PhysX. When it models smart particles (fragments) behavior, the data stream is relatively small, because these are pretty simple objects. However, if the particle systems are truly massive and there are millions of fragments involved, the data stream may increase so tremendously that the bandwidth of the PCI bus AGEIA PhysX uses to communicate with the graphics accelerator of the system may turn out insufficient to handle it. As a result, you will notice delays and jumps in the smooth gameplay process that will certainly affect the gamily experience in a negative way. It is pretty hard to estimate how probable this outcome actually is, but theoretically it is quite possible especially in the upcoming games that will use a lot of complex effects like that. This issue may only be resolved in the new model of PhysX solution supporting more high-performance PCI Express x1 interface.
• Finally, the last limiting factor may be the low-quality implementation of the physics engine in the game itself (of the hardware driver issues).