ARCH 481: 3D Modeling and Rendering, University of Washington, Department of Architecture
Glossary: Anti-aliasing
Anti-aliasing
DEFINITIONThe process whereby the "jaggies" or "stairstepping" caused by rasterization of geometric primitives is reduced through a blending or smoothing step that softens or slightly blurs the edges of the shape.
EXPLANATION
The term derives from the signal processing field. The term aliasing describes a phenomenon related to measuring recurrent processes. Your coo-coo clock may have a bird which pops out every hour on the hour, but if you only look up every 45 minutes, you might think it pops out only once every 3 hours.
OPERATION
There are two primary approaches to anti-aliasing, super-sampling and filtering.
The super-sampling approach rasterizes the image at a higher-than-displayed resolution, then blends pixel colors to create the displayed image.
The filtering approach rasterizes the image at display resolution, then smooths the image's edges with image-processing techniques. This is generally faster, but degrages the image more.
BENEFITS
At any spatial resolution an anti-aliased image will generally look "better" than one which has not been anti-aliased.
COSTS
As ever, the primary cost is TIME. The secondary cost is reduction in object definition. If you need to set an object's background to transparent, an anti-aliased edge is an irritation rather than a plus.
Last updated: May, 2014
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