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Sketch Express: Facial Expressions Made Easy
Jose Carlos Miranda, Xenxo Alvarez, Joao Orvalho, Diego Gutierrez, A. Augusto Sousa, Veronica Orvalho
Sketch based interface where strokes drawn on a canvas pose a face directly, independent of the underlying rig, so poses can be stored and reused across characters.
Abstract
Finding an effective control interface to manipulate complex geometric objects has traditionally relied on experienced users to place the animation controls. This process, whether for key framed or for motion captured animation, takes a lot of time and effort. We introduce a novel sketching interface control system inspired in the way artists draw, in which a stroke defines the shape of an object and reflects the user's intention. We also introduce the canvas, a 2D drawing region where the users can make their strokes, which determines the domain of interaction with the object. We show that the combination of strokes and canvases provides a new way to manipulate the shape of an implicit volume in space. And most importantly, it is independent from the 3D model rig. The strokes can be easily stored and reused in other characters, allowing retargeting of poses. Our interactive approach is illustrated using facial models of different styles. As a result, we allow rapid manipulation of 3D faces on the fly in a very intuitive and interactive way. Our informal study showed that first time users typically master the system within seconds, creating appealing 3D poses and animations in just a few minutes.
How to read this
- Category
- Academic paper proposing a sketch based control interface for posing faces
- Contributions
- Replaces placed animation controls with strokes: the artist draws the shape they want and the stroke reflects the intention directly
- Introduces the canvas, a 2D drawing region that scopes which part of the object a stroke acts on
- Makes the control layer independent of the 3D model rig, which is the claim that matters most for a rigger
- Because strokes are rig independent they can be stored and reused on other characters, giving pose retargeting for free
- Reports that first time users mastered the system within seconds in an informal study, producing poses and short animations in minutes
- Context
- This comes from the Porto group around Veronica Orvalho, and it is the interaction side of the same programme as their rig transfer work: if a rig can be moved between characters, so should the way you drive it. It also sits early in the sketch based posing line that later shows up in production at Pixar with Sketch to Pose and in research with SketchiMo.Builds on: Transferring the Rig and Animations from a Character to Different Face Models
- Correctness
- The usability claim rests on an informal study rather than a controlled one, and the authors say so, so read the seconds to master figure as an encouraging anecdote and not a measurement. The rig independence claim is the substantive one and is demonstrated across facial models of different styles. Note the scope: this is faces, and the strokes drive an implicit volume, so do not assume it transfers unchanged to a body rig.
- Clarity
- Short, readable and heavily illustrated, as sketch interface papers tend to be. The idea lands in a couple of figures, which is a good sign for something meant to be intuitive.
- How to read it
- First pass, look at the stroke and canvas figures, since the whole proposal is visual and you will understand it faster from the pictures than from the text. Second pass, read the section on independence from the rig, which is where the value for a character pipeline actually sits. A third pass is only worth it if you build animation UI, in which case compare its stroke model against what Presto ended up shipping.
Related work
Keywords
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