When taking samples within a pixel, the sample positions have to be determined in some way. The result of this method is that a higher number of samples are calculated only where necessary, thus improving performance. If these values are very similar, only these samples are used to determine the color. Initially only a few samples are taken within each pixel. A way around this problem is to use a technique known as adaptive supersampling, where only pixels at the edges of objects are supersampled. Supersampling is computationally expensive because it requires much greater video card memory and memory bandwidth, since the amount of buffer used is several times larger. Method Computational cost and adaptive supersampling As this approach would require a forward and inverse fourier transformation, computationally less demanding approximations like supersampling were developed to avoid domain switches by staying in the spatial domain ("image domain"). The number of samples determines the quality of the output.Īliasing is manifested in the case of 2D images as moiré pattern and pixelated edges, colloquially known as " jaggies".Ĭommon signal processing and image processing knowledge suggests that to achieve perfect elimination of aliasing, proper spatial sampling at the Nyquist rate (or higher) after applying a 2D Anti-aliasing filter is required. The result is a downsampled image with smoother transitions from one line of pixels to another along the edges of objects. This is achieved by rendering the image at a much higher resolution than the one being displayed, then shrinking it to the desired size, using the extra pixels for calculation. Color samples are taken at several instances inside the pixel (not just at the center as normal), and an average color value is calculated. The aim of supersampling is to reduce this effect. A line can only be shown as a collection of pixels, and therefore appears jagged unless it is perfectly horizontal or vertical. These pixels all have the same size, and each one has a single color. Aliasing occurs because unlike real-world objects, which have continuous smooth curves and lines, a computer screen shows the viewer a large number of small squares. a method used to remove aliasing (jagged and pixelated edges, colloquially known as " jaggies") from images rendered in computer games or other computer programs that generate imagery. Supersampling or supersampling anti-aliasing ( SSAA) is a spatial anti-aliasing method, i.e. (Not applying AA is analogous to a nearest-neighbor interpolation.) Comparison of a rendered scene without (left side) and with supersampling anti-aliasing applied (right).
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