Transparency antialiasing is a desirable feature that antialiases objects that are derived from alpha textures. The following example from 3Impact demonstrates how an alpha texture is created. Objects in the game world typically originate from basic geometric shapes, or primitives, which are antialiased using traditional multisampling algorithms. However, multisampling does not antialias objects that exist inside the geometry, such as an alpha texture.
Alpha Texture Mapping
Transparency antialiasing is configured through the driver by changing the view to advanced settings. After the advanced settings are enabled, the transparency antialiasing setting will appear near the end of the settings list. When checked, transparency antialiasing can be set to off, multisampling, or supersampling. Supersampling transparency antialiasing covers alpha test, alpha blend, and certain pixel shader functions, making it more effective than multisampling.
Transparency Antialiasing Setting
The following demonstration shows the effects of the various antialiasing settings in a scene from Far Cry's Regulator map. Click the links underneath the image to display the respective screenshot. Notice that in this example, both the 2X AA and 4X AA multisampling modes are ineffective in removing the jagged edges that appear on the tree and the crane's boom and wires.
Notice the effects of 8XS AA, which is also based on supersampling, but works on the entire scene or frame buffer. Supersampling is computationally and memory intensive because each frame is rendered at a much higher resolution than the resolution being displayed on the monitor.
The high resolution image data is saved in a special buffer, or area of graphics memory, and is then filtered and scaled back down to the display resolution. The best image quality was delivered by combining 8XS AA with supersampling transparency AA.
BENCHMARK RESULTS
How much graphics horsepower does it take to accelerate Far Cry under a high image quality setting at 1600x1200 with 8XS AA and supersampling transparency AA and the highest quality in-game settings enabled?
Far Cry Settings
A lot, but the GeForce 7900 GTX was up to the challenge as it provided excellent performance on the Athlon 64 X2 4800+ system in both single and SLI modes.
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