Super-sampling (SSAA or FSAA)
The first and most brute-force approach to
anti-aliasing in a 3D scene is super-sampling
AA (SSAA), which is also known as full-scene
AA (FSAA). Here, for every pixel of the final
image, instead of sampling the 3D scene
once, multiple samples of the scene are taken
at different locations within each pixel (sub-
samples). The result of these multiple tests is
thencombinedtoformthecolourofthefinal
pixel. Essentially, it’s the equivalent of rendering
the entire scene at a higher resolution, then
downsampling it to the final lower resolution.
This approach works very well, providing
a consistent AA effect across a broad range
of games that adds significantly to the
overall image quality. As a result, scenes look
more realistic and have more depth, lending
a smooth, almost filmic quality to them.
Older games that don’t employ particularly
sophisticated post-processing techniques
to improve image quality can be greatly
improved with the addition of SSAA.
However, there are a couple of major
downsides. The first is that it makes the whole
image look slightly soft, as the anti-aliasing
technique blends all pixels to the same level.
This effect is most noticeable on vertical or
horizontal lines, or on the textures used to
paint the outside of polygons that make up
a 3D scene. Some people find this softness
particularly distracting, while for others it’s far
less of an issue. We tend to feel the overall
image quality improvement compensates for
the slight loss in sharpness.Theother,morepressing,problemis the
huge performance cost. Because you’re
rendering every aspect of a scene multiple
times for each pixel, it takes far more
processing power. Although it doesn’t quite
scale linearly – as there are a few other factors
that determine overall performance – it’s a
rough rule of thumb that 2x SSAA will nearly
halve normal performance, 4x SSAA will
halve it again and 8x will, you’ve guessed it,
halve it again. In our testing, we saw a drop in
frame rate of 85 per cent between no AA and
8x SSAA. For this reason, it’s an option that’s
seldom offered in games, and Nvidia doesn’t
even include a way to force it on in its driver.
As a general tip, though, some games can
be made to look much better by turning downsome of the in-game detai
on SSAA in the driver. The overall smoothness
can make up for the loss of a few effects.Dynamic Super Resolution (DSR)
Nvidia doesn’t offer a conventional SSAA
option in its driver. Instead it has Dynamic Super
Resolution, which essentially offers the same
idea but almost in reverse. Here, Nvidia renders
the whole game – menus and all – at the higher
resolution and scales it back down. As a result,
this feature doesn’t work on games that don’t
support scalable user interfaces, or games with
maximum resolutions of 1,920 x 1,080.
You also have to jump through more hoops
than with conventional SSAA to get it working.
Rather than just enabling SSAA in the driver,
as with AMD, you have to jump into the Nvidia
driver and enable the DSR factors that you’d
like the game to be able to use. The driver then
tells the game that it can run at resolutions that
equate to the native resolution of your display
multiplied by that factor. So, for a 1.2x factor on
a 1,920 x 1,080 screen, you’re telling the game
that it can offer a resolution of 2,304 x 1,296,
which DSR will then scale back down to 1080p.
You can also select the smoothness of the final
image via a sliding scale.
On the other hand, it does offer the ability
to scale the game at peculiar resolutions, so
you can potentially find a better balance of
performance and image quality than with the
strict 2x, 4x and 8x modes for conventionalFOR EVERY PIXEL OF THE FINAL IMAGE, MULTIPLE
SAMPLES OF THE SCENE ARE TAKEN AT DIFFERENT
LOCATIONS WITHIN EACH PIXEL
From left to right: No AA, 2x SSAA, 4x SSAA and 8x SSAA