Custom PC - UK (2020-02)

Temporal AA (TAA)

There’s yet another general type of AA

that’s fundamentally different from both

the classic and the post-processing AA

techniques we’ve previously discussed, and

that’s because this type work across time.

No, we’re not talking time-travelling pixels

here, but TAA-type algorithms compare

aspects of a previous frame to the current

one, to help identify the colour of each pixel.

There are several techniques that use

the temporal AA principle. The first is the

most general form, which you’ll often find

labelled as just TAA in games. This is a

variation on post-processing techniques,

and it compares the previous frame to the

current one to help determine the best

colour for each pixel.

It does this by shifting the sampling

positions for each pixel in each frame,

and then averaging out the results when

calculating the final colour for each pixel.

There’s an exponential quality to this

algorithm, as each pixel is informed by the

last one, which in turn was informed by the

last one and so on.

In theory, this approach can make it quite

accurate. Where motion is involved, the

algorithm finds the history of any given

pixel by tracking the motion vector of that

pixel (an attribute that the game’s engine

can add to each sample location), in order

to find the current pixel’s location in the

previous frame. If the two are significantly

different, the algorithm performs a more

basic FXAA-style ‘nearest neighbour’

averaging technique.

The results of TXAA or TAA can be

impressive, with jaggies significantly

reduced and shimmering or pixel crawl

all but eliminated, without introducing a

distracting level of softness. However,

where fast motion is involved, TAA can look

blurry, making fast-response games, such

as first-person shooters, feel less clear and

more sluggish in action. Otherwise, though,

it’s a big step forwards in overall fidelity.

Multi-fra ed AA (MFAA)

MFAA is anoth hat adds an

element of time i r cessing but, unlike

TAA, it isn’t based on analysing previous

WE’RE NOT TALKING

TIMETRAVELLING

PIXELS HERE, BUT

TAATYPE ALGORITHMS

COMPARE ASPECTS OF A

PREVIOUS FRAME TO

THE CURRENT ONE

From left to right: No AA, FXAA, TAA