|
Anisotropic
Filtering :::...
One
of the fundamental elements of image quality is the
use of anisotropic filtering. Unlike the NV3x series
GPUs, the 6800 performa angle dependant filtering
that looks strikingly similar to the Radeon 9800's
way of doing things.
Optimised
trilinear filtering is still enabled by default though
this can now be disabled in the drivers.
The
examples below show how harsh the MIP transitions
are when optimised filtering is used (left) compared
to using regular filtering (right).
If
you look at that last example where we've combined
16x anisotropic filtering with 8xS antialiasing you'll
notice how the LOD bias has increased in keeping with
the 2x Super Sampling part of this mode. Texture noise
with this increased LOD didn't seem to be a major
issue but more time to test would have been preferred.
Being
angle dependant there are naturally some compromises
to image quality at certain angles though this was
something I didn't have sufficient time to demonstrate.
This isn't a big issue as we've all happily accepted
this mode of operation from ATi for the past few generations
and on blance it's a perfectly reasonable way to balance
performance with quality.
The
new 16x filtering mode was generally difficult to
warrant using in most cases as the visual differences
were minimal at best. I'm sure there are situations
where it will come into its own bust for most users
most of the time I see no reason to push the slider
past the "8x" mark.
Overall
it was hard to fault the quality of the filtering,
and the option to disable adaptive filtering and trilinear
optimisations now lets users dial in maximum image
quality when it's needed. What took them so long?
|
