CPU Test 2 – Physics

Finally, we have the Physics CPU test, which isn’t purely a CPU test. This test can also take advantage of Ageia’s PhysX PPU, and Nvidia says that it will shortly be able to take advantage of Nvidia’s CUDA-based PhysX when it becomes available too.

The last version of 3DMark also used Ageia’s PhysX engine, but this is the first benchmark that’s supported the hardware. Although many people consider Ageia’s PhysX PPU a bit redundant now, this test could prove to be quite important if hardware-accelerated PhysX does take off in games.

As with the AI test, this test also features a number of planes, but this time they’re all crashing into a number of objects. These include the ground, other planes and, most importantly, a series of gates. There are two types of gates; the ring-shaped ones made from tough, pressurised cloth, and the pole gates, which are made from an elastic foamy material. The idea is that these will simulate how the physics resulting from collisions with both cloth and soft-body obstacles.

Interestingly, the number of gates in the test is all down to your hardware. This test will split pairs of gates into different ‘worlds,’ which are independent from each other but have the same number of planes. The test will then assign one pair of gates to each core of your CPU and a further three to your PhysX PPU if you have one. According to Futuremark, a ‘world’ assigned to a CPU core will do all the calculations on the CPU, while those assigned to a PPU will do all the work on the PPU, with the exception of rigid body simulations, which are still done on the CPU. The reason for this split is apparently to prevent the need for the PPU to wait for the CPU to catch up before it can continue working, and vise-versa.

As well as the obstacles, the planes themselves are also constructed from 12 rigid pieces, which are connected via 11 breakable joints. However, according to Futuremark, the way in which the planes break up is completely unscripted, and entirely driven by the PhysX engine. The number of gates scales with your hardware as follows:

2 cores = 2 pairs of gates, or 5 with PPU
4 cores = 4 pairs of gates, or 7 with PPU
8 cores = 8 pairs of gates, or 11 with PPU

As with the AI test, this test again calculates the number of OPS by adding the number of appropriate calculations together, and dividing this figure by the time taken for the test to complete. In this case, one physics simulation step of one physics ‘world’ counts as one OP, and all the physics simulation steps across all the worlds are added together once the fixed-time test has completed.

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