2.5D Cartoon Models

Paper by:

Alec Rivers – MIT CSAILTakeo Igarashi – The University of Tokyo

Frédo Durand – MIT CSAIL

Overview

In the past, the only way to create 3D cartoon models was to render it in a non-photorealistic

way so it resembled a cartoon. The problem was that generating a 3D model is time

consuming and there are many stylistic elements that can’t be reproduced in a 3D model.

Overview

The authors proposed a way to use 2D vector art drawings of a cartoon from different angles to generate a new type of 2.5D cartoon structure. They claim that believable rotations can be achieved of 2D vector models in this manner. In this way, the 2.5D models maintain the nature of the 2D vector drawings they were created from.

Vector Art

In this drawing, you can see the front, left side and top views of the 2D vector art drawing. These are used to render the 2.5D cartoon.

2.5D Cartoon

This 2.5D cartoon is created with each of the strokes from the original drawing positioned in the appropriate position.

3D Cartoon

The 2.5D cartoon is then used to render a 3D version of the cartoon, which can then be rotated.

2.5D Interpolation

This picture shows a 2.5D model being rotated from a front view through it’s side view. The arrangement of strokes on the left is what’s required to be able to end up with a believable 3D rendering.

Z-Ordering

Many methods have been designed for handling Z-ordering of parts of a 3D render. With the method the authors came up with, Z-ordering is determined by the 3D position of each stroke and is handled automatically, although it can be overridden by the artist if desired.

User InterfaceHere is what the user interface looks like.

Parameterized Orientation Space

The authors parameterize the possible views into yaw and pitch. Tilt is ignored, as it can be accounted for with a screen space rotation.

Failure Case

In this failure example, they show that their algorithm has problems rendering the hair because of the outline not being well approximated by 2D linear interpolation.

Conclusion

While their video clearly shows this method is useful in creating 3D models from 2D drawings, there are limitations as to what it can do. Their method, however, allows the artist the ability to manually compensate for any issues the 3D model may have, such as image popping, etc…