Question: How Can 3D Animation Be Rendered As 2D Animation?
Numerous animated television shows and movies make use of 3D animation rendered to look 2D, inked lines and all. A prominent example is Family Guy; a few of my favorites that use this technique are Pucca and Blassreiter. Some use wholly 3D-rendered animation; others combine it with hand-drawn 2D. But how is it done?
Answer: There are numerous software packages that can create this effect, and each has a different methodology, but it boils down to determining the edges, base color, and shadow/highlight threshold of a shape. In the old days, it was possible to create a crude version of this in 3D Studio Max by playing with reflectivity and matte for applied textures, so that scene lighting displays on a surface so evenly it either seems to be a single color, or broken into a primary color, a single shadow color, and a single highlight color. This technique often uses an extreme shadow threshold to create the illusion of an outline.
More sophisticated software uses special algorithms to determine the edges of a shape, based on the scene lighting and the position of the camera. Shadow falloff often plays a key part in where the software will perceive the edge outline. The algorithm can apply edges to the outline, with control over the line style and weight. It also determines the optimal fill color, whether you're working with flat fill or with shaded fill. Usually the animator has control over the color fill.
This technique is often used to avoid having to animate complex figures by hand, such as machines with many parts. When used well, it can blend seamlessly into the 2D animation, until only a trained eye can tell the difference. When used poorly, it can detract from the overall animation by using poor-quality substitutes. (Speed Racer revamp, I'm looking at you.)
