Cel Shading

I decided to research several books to have some research into cel shading. The first book I read was.

Cel-shaded Animation:

Frederic P. Miller, Agnes F. Vandome, John McBrewster

"Cel-shaded animation (also called cel-shading or toon shading) is a type of non-photorealistic rendering designed to make computer graphics appear to be hand-drawn. Cel-shading is often used to mimic the style of a comic book or cartoon. It is a somewhat recent addition to computer graphics, most commonly turning up in console video games. Though the end result of cel-shading has a very simplistic feel like that of hand-drawn animation, the process is complex. The name comes from the clear sheets of acetate, called cels, which are painted on for use in traditional 2D animation, such as Disney classics."

 I also researched the book

 

Lightwave 3D 8 Texturing

 By Leigh Van der Byl

It states that cel shading is a process of rendering 3D objects so they appear flat or 2D as if part of a cartoon. Cel  is a term given to individual frames of drawn animation. A lot of television shows use subtle cel shading in their animation such as Futurama for example where it's used to integrate parts that are done in 3D into the 2D animation of the show itself. 
The cel shader works by altering the algorithm so that the surface no longer has smooth transitions between colours, turning them instead into flat bands of colour.
To use cel shading to its full potential, any objects being used with this shader should also be used with silhouette edges, unshared edges, sharp creases and surface borders.


And I also researched the book.

Manga Clip Art:

By Hayden Scott-Baron

It states that cel shading can be seen as a digital form of manga and that it refers to the style of using flat block colours to represent areas of light and shadow on a picture. This relates to the use of animation cels in Japanese anime. And the way that colours are used to define depth. The use of darker and lighter tones to define shape and shadow was so unique it says that it became intrinsically associated with Japanese animation. Western studios have also now adopted the technique; it is still something that helps to make authentic looking and aesthetically pleasing anime characters.

The appearance of cel shading is also very easy to emulate using photoshop by making the most of layers; it is possible to achieve a high quality look very quickly. The time can be spent focusing on the details rather than getting the overall cel look to work effectively.

It goes on to the say that cel shading is often the basis for many other visual styles, such as airbrush or natural media, and acts as the basis of lighting for most images. Time spent on the cel shading process will improve the look of a lot of images it says, whatever look you hope of achieving in the final piece.

 

Here are some screen captures of the book with an example and the importance of things such as shading, highlights and shadows in cel shaded animation.

 

 The pig has no shading, just simple base colors. The most important aspect of cel shading is understanding how light falls and how the shape of an object will affect the shading. 

 

The lightest parts of an object are those that face the light source and the darkest parts are those that face away from the light. Unless the light source is very small and weak the light will affects the object equally. In other words, about the same amount of light falls on all the areas that point toward the light.
The light source on this pig is originating from the top left, so any areas facing away from there have been shaded more darkly.

Effective definition of shadows can make all the difference to how solid your object looks. Firstly the pig casts a shadow onto the floor so the shape of its body has been defined. Secondly the pig is also casting a shadow onto itself you can see how some features of the pig are blocking the light onto the rest of its body. Sometimes you may wish to further define the shadows. Giving some areas heavier shadows can help define the shape of the object more vividly.

Highlights are only necessary on shiny materials and can be used a lot or a little depending on how you want the image to look and what effects is desired. In this image the main light source has been used as the main source of the highlights. However additional highlights have been added to imply another light source nearby. This can be used to give the object more volume.