Inbetweening with Occlusions for Non-Linear Rough 2D Animation
Inbetweening with Occlusions for Non-Linear Rough 2D Animation
Research Report RR-9559
- Univ. Bordeaux, CNRS, Bordeaux INP, Inria, LaBRI
Starting from the head-turn animation in Even et al. 2023 (bottom), with input key drawings in dark blue and automatic inbetweens in light blue, we use different features of our system to pro- duce an animation (top) with occlusions (e.g., ears). From left to right: masks are automatically computed for all drawing parts to create occlusions among them; a stroke is appearing through a temporal visibility threshold; a partial drawing of the nose is created at an intermediate frame (it is stored at a keyframe, but is made to appear later on via visibility); a stroke is made to disappear on the opposite ear, and it is suddenly interrupted by the “pop” of the right ear in front, via a layout change between keyframes. The final result conveys a strong 3D-like sense as shown in our video.
Abstract
Representing 3D motion and depth through 2D animated drawings is a notoriously difficult task, requiring time and expertise when done by hand. Artists must pay particular attention to occlusions and how they evolve through time, a tedious process. Computer-assisted inbetweening methods such as cut-out animation tools allow for such occlusions to be handled beforehand using a 2D rig, at the expense of flexibility and artistic expression.
In this work, we extend the more flexible 2D animation framework of Even et al. 2023 to handle occlusions. We do so by retaining three key properties of their system that are crucial to speed- up the animation process: input rough drawings, real-time preview, and non-linear animation editing. Our contribution is two-fold: a fast method to compute 2D masks from rough drawings with a semi-automatic dynamic layout system for occlusions between drawing parts; and an artist-friendly method to both automatically and manually control the dynamic visibility of strokes for self-occlusions. Such controls are not available in any traditional 2D animation software especially with rough drawings. Our system helps artists produce convincing 3D-like 2D animations, including head turns, foreshortening effects, out-of-plane rotations, overlapping volumes and even transparency.
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Bibtex
@techreport{Even:2024,
title = {Inbetweening with Occlusions for Non-Linear Rough 2D Animation},
author = {Even, Melvin and B{\'e}nard, Pierre and Barla, Pascal},
year = {2024},
number = {RR-9559},
institution = {{Inria ; Univ. Bordeaux, CNRS, Bordeaux INP, LaBRI, UMR 5800}},
}