This paper presents a method for creating coherently animated line
drawings that include strong abstraction and stylization effects.
These effects are achieved with active strokes: 2D contours that
approximate and track the lines of an animated 3D scene. Active
strokes perform two functions: they connect and smooth unorganized
line samples, and they carry coherent parameterization to support
stylized rendering. Line samples are approximated and tracked
using active contours (“snakes”) that automatically update their arrangment
and topology to match the animation. Parameterization
is maintained by brush paths that follow the snakes but are independent,
permitting substantial shape abstraction without compromising
fidelity in tracking. This approach renders complex models
in a wide range of styles at interactive rates, making it suitable for
applications like games and interactive illustrations.