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NVIDIA's next-gen gaming graphics card, GeForce GTX 980 revealed!

By Vijay Anand - 19 Sep 2014

Multi-Pixel Programmable Sampling with Multi-Frame Sampled AA (MFAA)

Multi-Pixel Programmable Sampling with Multi-Frame Sampled AA (MFAA)

The previous feature dealt with improving gaming quality when you have excess image processing horsepower for the game played. This next feature deals with the opposite scenario such as in Battlefield 4 that simply saps up your frame rates if you crank up the image quality setting all the way up. In this case, you would wish you had a more powerful graphics subsystem. But what if there was a way to deliver a similar level of image quality, but with more performance headroom?

Multi-Frame Sampled AA (MFAA) is NVIDIA's next trick up their sleeves to accomplish this. Unlike traditional MSAA that uses a fixed number of coverage samples per pixel on a rotated grid pattern, MFAA will use half the number of coverage samples but the coverage sample pattern differs per pixel and per frame. The resultant per-frame outcome will then be treated with a Temporal Synthesis Filter between these frames that would then seem to rival or equal what MSAA achieves, but at nearly half the performance penalty. Hence the namesake of this AA mode, which relies on multiple frames to derive its cumulative benefit.

Taking the most commonly used antialiasing level of 4x MSAA, 4x MFAA can rival 4x MSAA image quality but at 2x MSAA processing requirements. You could also benefit from the reduced performance overhead to get better imaging quality at no extra penalty (such as 8x MSAA quality at 4x MSAA performance levels). Let's step through this visually.

The difference between no antialiasing (AA) and 4x MSAA should be pretty straightforward to most gamers and graphics card enthusiasts.

As iterated earlier, MFAA uses less coverage samples but alters the sample pattern per pixel and in every frame. Take note of the math that indicates what level of the pixel is covered based on the coverage sample locations.

Applying a temporal filter between frames to counter frame variations, the final outcome of MFAA is unveiled. Take note of the math that determines the resultant level of pixel coverage.

As such, a "4x MFAA" setting achieves the equivalent of 4x MSAA from a visual standpoint but with much less processing overhead. Efficiency is the key here to unlock more performance by achieving the same or similar result.

To prove this point further, NVIDIA showed us a side-by-side comparison using the Portal 2 game. The resulting quality is indistinguishable on MSAA or MFAA.

In an actual in-game photo taken off a monitor, this is a 100% crop of 2x MSAA...

… while this is 4x MFAA which gives superior antialiasing that rivals 4x MSAA but at far less processing overhead; about equivalent to 2x MSAA.

Yet again, here's another example with a pinwheel - on the left half is 4x MSAA while the right half with the green border signifies 4x MFAA. It's practically impossible to tell them apart.

To get MFAA working, you'll need at least 40 FPS sustained with the new AA technique, otherwise you'll end up noticing flickering effects since the sample patterns will differ between frames. To manage this, MFAA will once again be left to GeForce Experience to determine whether your system has enough power to deliver this experience in your respective game. This will take away the guesswork and trial-and-error on your part, while giving gamers what they need most.

In terms of exact details on how much you stand to gain, NVIDIA estimates you'll get at least 30% more performance on 4x MFAA than if you were still running it on 4x MSAA. At 4x MFAA, since NVIDIA states its workload is similar to 2x MSAA, we queried if the extra Temporal filtering needs contribute to higher processing needs. In short, 4x MFAA will be a tad slower than 2x MSAA only because the Temporal filtering would sap up another 1 or 2% more performance overhead than standard 2x MSAA.

MFAA nets you more performance than MSAA can accord you. Fortunately, AA quality doesn't get compromised.

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