toonbanding

Toonbanding, or toon banding, is a digital image artifact that occurs in toon shading (cel shading) or stylized rendering when smooth tonal gradients are represented with a limited number of discrete color levels. In such images, regions that should transition gradually between light and dark instead display visible bands or steps, producing a posterized or segmented look.

Causes of toonbanding include low color depth, aggressive quantization in the shading pipeline, and compression that reduces color information. It is common in real-time rendering for video games and interactive applications that use simplified shading models, as well as in static images processed with limited palette constraints. The problem is exacerbated when gradients are mapped to a small set of presets or when gamma and color space are not handled consistently through the rendering pipeline.

Mitigation strategies involve increasing color precision and reducing quantization. Practical approaches include using higher bit depth per channel (for example, 16-bit or 32-bit), enabling dithering (spatial or temporal) to mask steps, and increasing the number of shading levels in the toon ramp or gradient. Adjusting gamma and working in an appropriate color space can also reduce perceptible banding. In real-time applications, temporal dithering or adding subtle noise across frames can lessen the visibility of bands during animation and motion.

In some cases, toonbanding is an intentional aesthetic choice, reflecting retro or stylized objectives. When it is unintentional, addressing the rendering pipeline, color management, and post-processing settings is the typical course of action. Related concepts include color quantization and gradient banding.