Computing & the Arts

2. Computer Graphics and Drawing

Monet's 4 trees.

Remember... the "holy grail" of CG was :

"Computer Graphics creates realistic pictures by mimicking the physics of light interaction with a visible scene, its objects, its observer."

In recent years, however, CG has opened another door, entering the realm of artistic renderings of reality or otherwise.
This new field of play, where scientists collaborate closely with artists or try to study their way of rendering pictures, has been coined "Non-Photorealistic Rendering" or NPR for lack of a better name.

"Computer graphics is the most versatile medium to ever be placed into the hands of visual artists. I challenge us all to find new ways to make use of this new medium."
Doug Cooper, "Personnal Thoughts on NPR," in [SIGGRAPH:NPR:1999].

Lecture Notes by Jonathan Cohen on Rendering Techniques (John Hopkins):

NPR: Pen-and-Ink Illustration
NPR: Painterly Rendering
NPR: Technical Illustration

Lecture Notes on Rendering Techniques, JHU, 1999.

Lecture Notes by Fredo Durand & Julie Dorsey (MIT):

Photorealism versus non-photorealism in CG

Lecture notes from "The Art and Science of Depiction," MIT, Spring 2001.

An example:
"Painterly Rendering for Video and Interaction"

by Aaron Hertzmann and Ken Perlin at NYU, 2000.

Abstract

We present new methods for painterly video processing. Based on our earlier still image processing technique, we ``paint over'' successive frames of animation, applying paint only in regions where the source video is changing. Image regions with minimal changes, such as due to video noise, are also left alone, using a simple difference masking technique. Optionally, brush strokes may be warped between frames using computed or procedural optical flow.

These methods produce video with a novel visual style distinct from previously demonstrated algorithms. Without optical flow, the video gives the effect of a painting that has been repeatedly updated and photographed, similar to paint-on-glass animation. We feel that this gives a subjective impression of the work of a human hand. With optical flow, the painting surface flows and deforms to follow the shape of the world.
Videos (local copies) :

Interactive painting exhibit .
Topaz music videos I and II .
Tower sequence : no flow , with optic flow , constant flow .
Subway sequence with optic flow .

More examples:

What Dreams May Come (1998): painterly rendering
Other Movies using these techniques

References

Janzen:NPRsurvey:1998

Janzen, T., "Ten Papers on Non-Photorealistic Rendering ," 1998, revised 1999.

SIGGRAPH:NPR:1999

Special section: "Focus: Non-Photorealistic Rendering," ACM SIGGRAPH, vol. 32, no.1, Feb. 1999.

Links

Reynolds:Survey:2004

Reynolds, C., "Stylized Depiction in Computer Graphics," 2004.

NPR reading group at Berkeley:

http://www.cs.berkeley.edu/~eden/npr/meeting/

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Last updated: Nov. 17, 2005.