Cel shading. Cel shading or toon shading is a type of non-photorealistic rendering designed to make 3D computer graphics appear to be flat by using less shading color instead of a shade gradient or tints and shades.  A cel shader is often used to mimic the style of a comic book or cartoon and/or give the render a characteristic paper-like texture. There are similar techniques that can make an image look like a sketch, an oil painting or an ink painting. The name comes from cels (short for celluloid), clear sheets of acetate which are painted on for use in traditional 2D animation.

Basic process 

The cel-shading process starts with a typical 3D model.  Where cel-shading differs from conventional rendering is in its non-photorealistic shading algorithm.  Conventional smooth lighting values are calculated for each pixel and then quantized to a small number of discrete shades to create the characteristic "flat look", where the shadows and highlights appear as blocks of color rather than being smoothly mixed in a gradient.

Outlines

Wireframe method
Black ink outlines and contour lines can be created using a variety of methods. One popular method is to first render a black outline, slightly larger than the object itself. Back-face culling is inverted and the back-facing triangles are drawn in black. To dilate the silhouette, these back-faces may be drawn in wireframe multiple times with slight changes in translation. Alternatively, back-faces may be rendered solid-filled, with their vertices translated along their vertex normals in a vertex shader.  After drawing the outline, back-face culling is set back to normal to draw the shading and optional textures of the object.  Finally, the image is composited via Z-buffering, as the back-faces always lie deeper in the scene than the front-faces.  The result is that the object is drawn with a black outline and interior contour lines.  The term "cel-shading" is popularly used to refer to the application of this "ink" outlining process in animation and games, although originally the term referred to the flat shading technique regardless of whether the outline was applied.

The Utah teapot rendered using cel shading:

 The back faces are drawn with thick lines
 The object faces are drawn using a single color
 Shading is applied

Steps 2 and 3 can be combined using multitexturing (part of texture mapping).

Edge-detection method

In video games 

The Sega Dreamcast title Jet Set Radio, which was revealed at the 1999 Tokyo Game Show, drew media attention for its cel-shaded style. It used cel-shading for its characters and its vibrant visual style has had a lasting influence on the use of cel-shading in video games. Since the early 2000s, many notable video games have made use of this style, such as Cel Damage (2001), The Legend of Zelda: The Wind Waker (2002) and Ōkami (2006).

Cel shading, in contrast to other visual styles such as photorealism, is often used to lend a more artistic or fantastical element to a video game's environment. In developing Ōkami, director Hideki Kamiya described his vision for the game's graphics: "I wanted to create a game with the natural beauty of the Japanese countryside... to make a world that was glistening and beautiful." Producer Atsushi Inaba recalls in a 2004 interview that Clover Studios had "abandoned the realistic style" for Ōkami as they became inspired by traditional Japanese art.

Game studios might choose a style such as cel shading in their development for reasons beyond artistic vision. Cel shaded graphics are usually simple in visual information, which can be useful in some applications. In the case of The Legend of Zelda: The Wind Waker, developer Satoru Takizawa states that using this style allowed to "represent the mechanisms and objects for puzzles [in The Wind Waker] in a more easy-to-understand way." Takizawa also argues that photorealistic graphics, in contrast, would have "had the adverse effect of making information difficult to represent game-wise."

Lists of cel-shaded media

Film

 Technological Threat, a 1988 American animated short made by Brian Jennings and Bill Kroyer and was produced by Kroyer Films.
 DuckTales the Movie: Treasure of the Lost Lamp, a 1990 American animated adventure fantasy film based on the animated television series DuckTales.
 Tom and Jerry: The Movie, a 1992 American animated musical comedy film based on the characters Tom and Jerry created by William Hanna and Joseph Barbera. 
 Felidae, a 1994 German adult animated mystery film directed by Michael Schaack, written by Martin Kluger, Stefaan Schieder and Akif Pirinçci, and based on Pirinçci's 1989 novel of the same name.
 The Rugrats Movie (1998)
 Tarzan, a 1999 American animated adventure film based on the 1912 story "Tarzan of the Apes" by Edgar Rice Burroughs.
 The Adventures of Rocky and Bullwinkle (2000)
 Help! I'm a Fish, a 2000 Danish-German-Irish traditionally animated science fantasy musical film.
 Rugrats in Paris: The Movie (2000)
 The Land Before Time VII: The Stone of Cold Fire, a 2000 American direct-to-video animated adventure musical drama and the seventh film in The Land Before Time series, produced and directed by Charles Grosvenor.
 The Little Polar Bear, a 2001 German animated film based on Hans de Beer books.
 Spirit: Stallion of the Cimarron, a 2002 American animated Western film.
 Lilo & Stitch, a 2002 American animated science-fiction comedy-drama film.
 Treasure Planet a 2002 American animated science-fiction adventure film.
 Rugrats Go Wild (2003)
 Stitch! The Movie, a 2003 American direct-to-video animated science fiction comedy film
 Brother Bear, a 2003 American animated musical fantasy comedy-drama film.
 Hot Wheels: World Race, a 2003 animated direct-to-video film.
 Appleseed, a 2004 Japanese animated film.
 Mickey, Donald, Goofy: The Three Musketeers, a 2004 American animated direct-to-video musical adventure film based on the film adaptations of the 1844 novel The Three Musketeers by Alexandre Dumas and the Mickey Mouse film series by Walt Disney and Ub Iwerks. 
 Lilo & Stitch 2: Stitch Has a Glitch, a 2005 American direct-to-video animated science fiction comedy-drama film produced by the Australian office of Disneytoon Studios.
 Stuart Little 3: Call of the Wild, a 2005 American animated comedy film.
 Leroy & Stitch, a 2006 American animated science fiction comedy television film produced by Walt Disney Television Animation.
 Disney DVD Game World: Disney Dogs Edition (2006)
 The Simpsons Movie, a 2007 American animated comedy film based on the Fox animated sitcom The Simpsons by Matt Groening. 
 Garfield Gets Real (also known as Garfield 3D in some regions), a 2007 American animated adventure comedy film based on the comic strip Garfield. 
 Chocolate, a 2008 Thai martial arts film starring Yanin "Jeeja" Vismistananda in her debut film performance. It is directed by Prachya Pinkaew, with martial arts choreography by Panna Rittikrai. It also stars Hiroshi Abe and Pongpat Wachirabunjong.
 Paperman, a 2012 American black-and-white computer-cel animated short film.
 Sofia the First: Once Upon a Princess (2012)
 Khail Girban's The Prophet, a 2014 animated film computer cel.
 Feast, a 2014 American 2D animated romantic comedy short film.
 The Peanuts Movie (2015)
 Mutafukaz: Operation Blackhead, a 2017 crime short film that became the basis for the comic book for the same name produced by Run.
 Spider-Man: Into the Spider-Verse (2018)
 Tom & Jerry (2021)
 Chip 'n Dale: Rescue Rangers (2022)
 Spider-Man: Across the Spider-Verse (2023)
 Nimona (2023)
 Once Upon a Studio, a 2023 American live-action/animated fantasy comedy crossover short film.
 Wish, a 2023 American animated musical film.
 Big City Greens the Movie: Spacecation, a 2024 American animated science fiction musical comedy film directed by Anna O'Brian and based on the Disney Channel animated television series Big City Greens, created by The Houghton Brothers.
 Coyote vs. Acme (TBA)

Television
 TaleSpin - an American animated television series first aired in 1990 as a preview on Disney Channel and later that year as part of The Disney Afternoon. 
 Mighty Ducks - a 1996 American animated television series.
 Futurama - a 1999 animated science fiction sitcom created by Matt Groening for the Fox Broadcasting Company and later revived by Comedy Central, and then Hulu. 
 Molly, Star-Racer - a 2001 French television pilot produced by Sparx Animation Studios
 Finger Tips - a 2001 British children's television series that aired on CITV and was broadcast from 3 September 2001 to 14 December 2008. It was produced by The Foundation.
 Spider-Man: The New Animated Series - a 2003 Canadian-American television series produced by Mainframe Studios, Marvel Enterprises, Adelaide Productions, and Sony Pictures Television
 Boo! - a 2003 British television series produced by Tell-Tale Productions
 Lilo & Stitch - a 2003 American animated television series produced by Walt Disney Television Animation
 Dragon Booster - a 2004 Canadian television series produced by Nerd Corps Entertainment
 Handy Manny - a 2006 American-Canadian children's television series produced by Nelvana
 Z-Squad - a 2006 South Korean-Canadian magical girl television series produced by Enemes, SBS, CJ Entertainment, Daiwon C&A Holdings and Nelvana, SOVIK
 The Land Before Time - a 2007 American animated television series, based on The Land Before Time film series created by Judy Freudberg and Tony Geiss
 Storm Hawks - a 2007 Canadian television series produced by Nerd Corps Entertainment
 League of Super Evil - a 2009 Canadian television series produced by Nerd Corps Entertainment
 Max Steel a 2013 American-Canadian television series produced by Nerd Corps Entertainment, Mattel
 Bunny Maloney - a 2009 French television series produced by MoonScoop Group, France 2, and Telegael
 Iron Man: Armored Adventures - a 2009 French-American television series produced by Marvel Animation
 Hot Wheels Battle Force 5 - a 2009 Canadian television series produced by Nerd Corps Entertainment and Nelvana
 Rated A for Awesome - a 2011 Canadian television series produced by Nerd Corps Entertainment
 Slugterra a 2012 Canadian television series produced by Nerd Corps Entertainment
 Sofia the First, a 2013 American animated fantasy children's television.
 Last Week Tonight with John Oliver - a 2014 American late-night talk and news satire television series produced by HBO - Episode 7: Immigration Reform
 Alvinnn!!! and the Chipmunks - a French-American animated musical comedy television series created by Janice Karman. Produced by Bagdasarian Productions and Technicolor Animation Productions (formerly known as OuiDo! Productions in season 1) with the participation of M6, it features Alvin and the Chipmunks and the Chipettes and marks their first television appearance together since 1990. First announced by Bagdasarian Productions in 2010, a promotional trailer for the series was posted on YouTube.

Animation and half of the show's storyboards are handled by Technicolor Productions in France, while Bagdasarian Productions in the U.S. is in charge of voice recording and music production. The series is primarily distributed by PGS Entertainment, a French brand management company. It premiered on M6 on March 30, 2015. In August 2015, Nickelodeon acquired the American broadcast rights to the series. It also airs in Teletoon and Family Channel in Canada.
 Regal Academy - a 2016 Italian television series produced by Rainbow S.p.A.
 Disenchantment - a 2018 American animated satirical fantasy sitcom created by Matt Groening for Netflix.
 Star Wars Resistance - a 2018 American television series produced by Lucasfilm Animation
 Love, Death & Robots a 2019 American Adult animated anthology series produced by Blur Studio for Netflix
 What If...? - a 2021 Marvel Studios alternate history television series set in the Marvel Cinematic Universe
 Arcane - a 2021 an adult animated steampunk action-adventure television series created by Christian Linke and Alex Yee. It was produced by the French animation studio Fortiche
 Your Friendly Neighborhood Spider-Man - an upcoming American animated television series created by Jeff Trammell for the streaming service Disney+, based on the Marvel Comics character Spider-Man.

Video games

See also 
2.5D
Gooch shading
Low poly

References

External links 
 IGN: Jet Set Radio review. Retrieved August 4, 2005.
 GameDev.net – Cel-Shading. Retrieved August 5, 2005 (Wayback Machine copy).
 sunandblackcat.com – Cel-Shading. Retrieved August 7, 2014.

Animation techniques
 
Computer animation
Shading
Video game graphics