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Sketch Express: Facial Expressions Made Easy

Miranda, J.M ; Alvarez, X. ; Orvalho, J. ; Gutierrez, D. G. ; Sousa, A.A.S ; Orvalho, V.

Computers and Graphics Vol. 36, Nº 6, pp. 585 - 595, March, 2012.

ISSN (print): 0097-8493
ISSN (online): 0097-8493

Journal Impact Factor: 1,176 (in 2016)

Digital Object Identifier:

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One of the most challenging tasks for an animator is to quickly create convincing facial expressions. Finding an effective control
interface to manipulate facial geometry has traditionally required experienced users (usually technical directors), who create and
place the necessary animation controls. Here we present our sketching interface control system, designed to reduce the time and
effort necessary to create facial animations. Inspired in the way artists draw, where simple strokes define the shape of an object,
our approach allows the user to sketch such strokes either directly on the 3D mesh or on two different types of canvas: a 2D fixed
canvas or more flexible 2.5D dynamic screen-aligned billboards. In all cases, the strokes do not control the geometry of the face,
but the underlying animation rig instead, allowing direct manipulation of the rig elements. Additionally, we show how the strokes
can be easily reused in different characters, allowing retargeting of poses on several models. We illustrate our interactive approach
using varied facial models of different styles showing that first time users typically create appealing 3D poses and animations in
just a few minutes. We also present in this article the results of a user study. We deploy our method in an application for an
artistic purpose. Our system has also been used in a pioneer serious game context, where the goal was to teach people with Autism
Spectrum Disorders (ASD) to recognize facial emotions, using real time synthesis and automatic facial expression analysis.