Fast approximate anti-aliasing

Comparison between (from left to right)Without anti-aliasing, 4x MSAA, and FXAA.

Fast Approximate Anti-Aliasing (FXAA) is an anti-aliasing algorithm created by Timothy Lottes under NVIDIA.^[1]

Advantages

• Does not require large amounts of computing power, achieved by smoothing jagged edges ("jaggies")^[2] according to how they appear on screen as pixels, rather than analyzing the 3D models itself as in conventional anti-aliasing.^[1]
• Smooths edges in all pixels on the screen, including those inside alpha-blended textures and those resulting from pixel shader effects, which were previously immune to the effects of multisample anti-aliasing (MSAA).^[3]

Disadvantages

• Textures may not appear as sharp if they are included in the edge detection.
• Must be applied before rendering the HUD elements of the game, lest it affect them too.

Processes

FXAA processing illustrations

The processes of FXAA are listed as follows:

• Find all edges contained in the image.

Finding edges is typically a depth-aware search, so that pixels which are close in depth are not affected. This helps to reduce blurring in textures, since edges in a texture have similar depths.

• Smooth the edges.

Smoothing is applied as a per-pixel effect. That is, there is no explicit representation of the edges. Rather, the first step is a depth-aware edge filter, which marks pixels as belonging to edges, and the second step filters the color image values based on the degree to which a pixel is marked as an edge.

References