ATI Technologies X850 - Radeon Xt Platinum Edition 256 Mb Agp, Руководство пользователя

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CrossFire™ Rendering Modes 13
Some types of textures, especially those with transparent portions, can
exhibit aliasing that is not removed by MSAA techniques. Another form of
anti-aliasing, known as Super-sample Anti-aliasing (SSAA), can be useful
in these cases, because it affects every pixel in an image. Although it
normally operates more slowly than MSAA, the power of multiple GPUs
can make SSAA practical to use.
SSAA first renders a scene at a higher resolution than that which is output
to the display, which is then downsampled to the display’s resolution. This
approach normally has two main disadvantages: it requires rendering many
more pixels than normal, which can have a drastic impact on performance,
and that it results in an ordered grid sample pattern, which does a poor job
of anti-aliasing some types of jagged edges. CrossFire™’s Super Anti-
aliasing overcomes both of these problems. It takes advantage of the second
GPU to render the additional pixels required for each frame, so there is little
or no performance impact. It can also make use of a more effective sample
pattern that does a better job of anti-aliasing near-horizontal and near-
vertical edges, resulting in better overall image quality.
Two of the new Super Anti-aliasing modes use a combination of MSAA
and SSAA to achieve the ultimate in image quality. They work by not only
using different multi-sample locations on each GPU, but also by offsetting
the pixel centers slightly. In effect, each GPU renders the image from a
different viewpoint, about half a pixel width apart. The new 10x and 14x
Super Anti-aliasing modes operate in this manner, combining 2x SSAA
with 4x and 6x MSAA, respectively.
Both of these modes work together with SmoothVision™ HD Anisotropic
Filtering (AF). This filtering technique produces sharper, clearer textures
by blending multiple texture samples (2, 4, 8, or 16) for each pixel. Because
Super Anti-aliasing can render each pixel from two slightly different
viewpoints and combine them, the texture samples from each viewpoint are
combined as well. This means the number of texture samples per pixel is
effectively doubled, so up to 32x Anisotropic Filtering can be supported.
The new Super Anti-aliasing modes can be enabled by users through the
ATI Catalyst™ Control Center interface.
2 Radeon® X850 CrossFire Edition Master Graphics Card
3 Partial Frame Rendered on PCI Express® Slave Graphics Card
4 Partial Frame Rendered on PCI Express® Master Graphics Card
5 Final Rendered Frame on Display