Spatio-Temporal Analysis for Parameterizing Animated Lines
Bert Buchholz, Noura Faraj, Sylvain Paris, Elmar Eisemann and Tamy Boubekeur NPAR 2011
Abstract
We describe a method to parameterize lines generated from animated 3D
models in the context of animated line drawings. Cartoons and
mechanical illustrations are popular subjects of non-photorealistic
drawings and are often generated from 3D models. Adding texture to
the lines, for instance to depict brush strokes or dashed lines,
enables greater expressiveness, e.g. to distinguish between visible
and hidden lines. However, dynamic visibility events and the evolving
shape of the lines raise issues that have been only partially
explored so far. In this paper, we assume that the entire 3D animation is known ahead of time, as is
typically the case for feature animations and off-line rendering.
At the core of our method is a geometric formulation of the problem
as a parameterization of the space-time surface swept by a 2D line
during the animation. First, we build this surface by extracting
lines in each frame. We demonstrate our approach with silhouette
lines. Then, we locate visibility events that would create
discontinuities and propagate them through time. They decompose the
surface into charts with a disc topology. We parameterize each chart
via a least-squares approach that reflects the specific requirements
of line drawing. This step results in a texture atlas of the
space-time surface which defines the parameterization for each
line. We show that by adjusting a few weights in the least-squares
energy, the artist can obtain an artifact-free animated motion in a
variety of typical non-photorealistic styles such as painterly
strokes and technical line drawing.
Resources
BibTex Reference: @inproceedings{Buchholz:2011:tcoco,
author = {Bert Buchholz and Noura Faraj and Sylvain Paris and Elmar Eisemann and Tamy Boubekeur},
title = {Spatio-Temporal Analysis for Parameterizing Animated Lines},
booktitle ={International Symposium on Non-Photorealistic Animation and Rendering (NPAR) 2011},
year = {2011},
}
