GeForce GTX 980 Whitepaper
ADVANCING THE STATE-OF-THE-ART
IN IMAGE QUALITY
27
Advancing the State-Of-The-Art in Image Quality
Game developers and GPU vendors are increasingly implementing more advanced forms of anti-aliasing
(AA) to enhance image quality. GM2xx GPUs have a number of new features for much more flexible
sampling, enabling further advancements in AA quality and efficiency.
Today’s GPUs ship with fixed sample patterns for AA that are stored in ROM. When gamers select 2x or
4xMSAA for example, the pre-stored sample patterns are used. While many current games implement
deferred, post-processed AA techniques such as FXAA or SMAA, there are still many others that
continue to use traditional hardware-based multi-sample AA (MSAA). GM2xx GPUs support multi-pixel
programmable sampling for rasterization, providing opportunities for more flexible and novel AA
techniques to be implemented in the context of both deferred and conventional forward rendering.
With programmable sample positions, the ROMs that were used to store the standard sample positions
are replaced with RAMs. The RAMs may be programmed with the standard patterns, but the driver or
application may also load the RAMs with custom positions which are free to vary from frame to frame or
even within a frame. In a 16x16 grid per pixel, we have 256 different locations to choose from for each
sample. We’ve also extended this programmable sample location support to span multiple pixels, so for
example in 4x MSAA rendering, all 16 samples within a 2x2 pixel footprint can be located arbitrarily. This
sample randomization can greatly reduce the quantization artifacts (like stair-stepping) that occur with
more traditional forms of AA. These freely specified sampling positions may be used in the development
of effective new algorithms.
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