Anti-Aliasing Menu

The Anti-Aliasing menu (Filter > Anti-Aliasing > ...) controls the level of anti-aliasing applied to an image during the rendering. Anti-aliasing is a technique that improves the image quality by reducing the edge pixelation effect that may appear in filters whose output includes hard edges, lines or shapes:

For rendering, Filter Forge uses the procedural approach – it builds an image function based on the filter component tree and evaluates it for every pixel of the resulting image. When anti-aliasing is turned on, a single pixel is rendered using multiple evaluations – or 'samples' – of the image function. The results of these samples are averaged to produce the anti-aliased pixel. In Filter Forge, there are 7 levels of anti-aliasing ranging from 5 to 65 samples per pixel:

Off – no anti-aliasing is performed, the image is rendered with one sample per pixel.

5 Samples – 65 Samples – these options define the number of samples used to evaluate each anti-aliased pixel of the image. The higher the number of samples, the better the result. However, higher number of samples slows down the rendering – for example, 16 samples per pixel make the rendering of that pixel 16 times longer than the rendering with 1 sample per pixel. The recommended setting is 5 to 9 samples. For filters that output hard edges, geometric patterns, or highly detailed reflective surfaces, the recommended setting is 17 to 25 samples.

Edges Only – activates the smart anti-aliasing algorithm. In this case, anti-aliasing is applied only to pixels that are located near the hard edges, and, for Surface filters (those that use Lighting), in high-frequency areas of the height map. In the majority of filters, such areas usually occupy a small percentage of the entire image area, so turning the Edges Only option on can significantly speed up the rendering without a visible loss in the image quality.

All Pixels – when this option is selected, anti-aliasing is applied to all pixels of the image, the smart anti-aliasing algorithm is not used. Turning this option on can significantly slow down the rendering, while the quality improvement is usually marginal.

Jittered Sampling

Normally, Filter Forge uses a regular grid pattern for placing samples within a pixel which is being anti-aliased. For filters that output high-frequency geometric patterns, the grid-based sampling may result in undesirable artifacts such as bands or moire-like patterns. This effect can be reduced by using jittered sampling which randomizes the sample positions within an anti-aliased pixel – this breaks the unwanted patterns by replacing them with noise. To turn jittered sampling on, use the Jittered Sampling option in Rendering Options.