Cel-shaded animation

Cel-shaded animation or cel-shading is the art of turning computer graphics into cartoon and comic book style art and attempting to mimic a more stylistic cartoon style, such as charcoal, watercolors or etching. Cel-shading is a sharp contrast to photorealistic graphics. It is a relatively recent addition to computer graphics, most commonly turning up in console video games. Though the end result of cel-shading has a very simple and retro feel, reminiscent of older hand drawn animation, the process is complex.

Process

The cel-shading process starts with typical 3D modelling under the hood. The difference occurs when a cel-shaded object is drawn onscreen. The rendering engine only selects a few shades of each color for the object, producing a flat look. This is not the same as using only a few shades of texture for an object, as lighting and other environmental factors would come into play and ruin the effect. Therefore, cel-shading is often implemented as an additional rendering pass after all other rendering operations are completed.

In order to draw the black ink lines outlining an object's contours, the back-face culling is inverted to draw back-faced triangles with black-coloured vertices. The vertices must be drawn either multiple times with a slight change in translation to make the lines "thick". This produces a black-shaded silhouette. The back-face culling is then set back to normal to draw the shading and optional textures of the object. Z-buffering does the magic because the back-faces always lie deeper in the scene than the front-faces, so the result is the object drawn with black outlines, even contours that reside inside the object's surface in screen space.

Appearances

Cel-shaded art has appeared in the following places:

• Cel-shaded video games
  • Tales of Symphonia
  • The Legend of Zelda: The Wind Waker
  • Wacky Races
  • Jet Set Radio series
  • Looney Tunes Space Race
  • Viewtiful Joe series
  • Cel Damage
  • Auto Modelista
  • Killer 7
  • XIII
  • Sly Cooper series
  • Tokimeki Memorial3 ~ Yakusoku no Ano Basho de ~
  • The Animatrix short films
  • ICO (for the character of Yorda)
  • Ostrich Runner