PC Graphics Options Explained
HARDWARE
Trilinearfilteringhelps,buttheground
still looks all blurry. This is why we use
anisotropic filtering, which improves
texture quality at oblique angles.
To understand why, visualise a
square window – a pixel of a 3D model
- with a brick wall directly behind it as
our texture.
Light is shining through the window,
creating a square shape on the wall.
That’s our sample area for this pixel, and
it’s equal in all directions. With bilinear
Anisotropic filtering
and trilinear filtering, this is how
textures are always sampled. If the
model is also directly in front of us,
perpendicular to our view, that’s fine,
but what if it’s tilted away from us?
If we’re still sampling a square,
we’re doing it wrong, and everything
looks blurry. Imagine now that the brick
wall texture has tilted away from the
window. The beam of light transforms
into a long, skinny trapezoid covering
much more vertical space on thetexture than horizontal. That’s the
area we should be sampling for this
pixel, and in the form of a rough analogy,
this is what anisotropic filtering takes
into account. It scales the mipmaps in
one direction (like how we tilted our
wall) according to the angle we’re
viewing the 3D object.
This is quite a difficult concept to
grasp, and I have to admit that my
analogy does little to explain the actual
implementation of it.PERFORMANCE
Anisotropic filtering it’s not nearly as much of a hit as anti-aliasing, which is why it rarely appears in
menus these days – it’s just on, no matter what. Using the BioShock Infinite benchmarking tool, I only
saw average FPS drop by six between bilinear filtering and 16x anisotropic filtering. That’s not much of
a difference considering the huge quality increase. High texture quality is pointless with poor filtering.
WHATdOTHE
NuMBERSMEAN?Anisotropic filtering isn’t common in
modern settings menus anymore,
but where it does appear, it generally
comes in 2x, 4x, 8x, and 16x flavours.
Nvidia describes these sample rates
as referring to the steepness of the
angle the filtering will be applied to,
“AF can function with anisotropy
levels between 1 (no scaling) and 16,
defining the maximum degree which
a mipmap can be scaled by, but AF is
offered to the user in powers of two:
2x, 4x, 8x, and 16x. The difference
between these settings is the
maximum angle that AF will filter the
texture by. For example: 4x will filter
textures at angles twice as steep as
2x, but will still apply standard 2x
filtering to textures within the 2x
range to optimise performance.
There are diminishing returns with
the use of higher AF settings
because the angles at which they are
applied become rarer.”Trilinear filtering Anistropic filteringBilinear filtering 16x Anistropic filtering