Relevant to Blender v2.32

A computer generated image is made up of pixels, these pixels can of course only be a single colour. In the rendering process the rendering engine must therefore assign a single colour to each pixel on the basis of what object is shown in that pixel.

This often leads to poor results, especially at sharp boundaries, or where thin lines are present, and it is particularly evident for oblique lines.

To overcome this problem, which is known as Aliasing, it is possible to resort to an Anti-Aliasing technique. Basically, each pixel is 'oversampled', by rendering it as if it were 5 pixels or more, and assigning an 'average' colour to the rendered pixel.

The buttons to control Anti-Aliasing, or OverSAmple (OSA), are below the rendering button in the Render Panel (Figure 17.12, “Render Panel.”). By pressing the OSA button antialiasing is activated, by selecting one of the four numeric buttons below it, the level of oversampling (from 5 to 16) is chosen.

Figure 17.12. Render Panel.

Blender uses a Delta Accumulation rendering system with jittered sampling. The values of OSA (5, 8, 11, 16) are pre-set numbers that specify the number of samples; a higher value produces better edges, but slows down the rendering.

Another parameter that can improve picture quality when using OSA is the Gaussian filter, also located in the Render panel. By pressing the Gauss button the filter is activated. The numeric slider to the right of the Gauss button defines the size of the sample mask. The sub-pixel sample creates a small weighted mask with the defined size, which also can affect neighbouring pixels as well. The result is smoother edges, less sensitive for gamma, and well suited to reduce motion-aliasing. (Figure 17.12, “Render Panel.”)

Figure 17.13, “Rendering without OSA (left) with OSA=5 (center) and OSA=8 (right).” shows a rendering with OSA turned off and with 5 or 8 OSA samples.

Figure 17.13. Rendering without OSA (left) with OSA=5 (center) and OSA=8 (right).