Non-linear Rough 2D Animation using Transient Embeddings
Non-linear Rough 2D Animation using Transient Embeddings
Computer Graphics Forum (Eurographics), 2023, 42, pp. 411-425
- Univ. Bordeaux, CNRS, Bordeaux INP, Inria, LaBRI
Our rough animation system supports the inbetweening of complex special effects with multiple topological events, here a flame splitting into smaller sparks. In (a), we show the input key drawings traced over a reference from Gilland’s book Gil09 and, in (b), their decomposition with a unique color per embedding – we made the colors consistent from one keyframe to the next for visualization purposes, but each embedding is effectively independent. Topological changes occur at the third and fifth keyframes. In (c), we display in magenta a subset of the inbetween frames generated by our system. Please see the supplemental video for the full sequence.
Abstract
Traditional 2D animation requires time and dedication since tens of thousands of frames need to be drawn by hand for a typical production. Many computer-assisted methods have been proposed to automatize the generation of inbetween frames from a set of clean line drawings, but they are all limited by a rigid workflow and a lack of artistic controls, which is in the most part due to the one-to-one stroke matching and interpolation problems they attempt to solve. In this work, we take a novel view on those problems by focusing on an earlier phase of the animation process that uses rough drawings (i.e., sketches). Our key idea is to recast the matching and interpolation problems so that they apply to transient embeddings, which are groups of strokes that only exist for a few keyframes. A transient embedding carries strokes between keyframes both forward and backward in time through a sequence of transformed lattices. Forward and backward strokes are then cross-faded using their thickness to yield rough inbetweens. With our approach, complex topological changes may be introduced while preserving visual motion continuity. As demonstrated on state-of-the-art 2D animation exercises, our system provides unprecedented artistic control through the non-linear exploration of movements and dynamics in real-time.
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Bibtex
@article{Even:2023,
title = {Non-linear Rough 2D Animation using Transient Embeddings},
author = {Even, Melvin and B{\'e}nard, Pierre and Barla, Pascal},
year = {2023},
journal = {Computer Graphics Forum},
month = may,
volume = {42},
number = {411-425},
articleno = {},
url = {https://doi.org/10.1111/cgf.14771},
doi = {10.1111/cgf.14771}
}