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Direct manipulation of blendshapes using a sketch-based interface
Confines blendshape direct manipulation to a geodesic neighbourhood and drives it from a sketch interface, so a drag edits local geometry instead of the whole face.
Abstract
We introduce a method that localizes the direct manipulation of blendshape models for facial animation with a customized sketch-based interface. Direct manipulation methods address the problem of cumbersome weight editing process using the traditional tools with a practical "pin-and-drag" operation directly on the 3D facial models. However, most of the direct manipulation methods have a global deformation impact, which lead to unintuitive and unexpected results. To this end, we propose a new way to localize the theory of direct manipulation method, using geodesic circles for confining the edits to the local geometry. Inspired by artists' brush painting on canvas, we additionally introduce a sketch-based interface as an application that provides direct manipulation and produces expressive facial poses efficiently and intuitively. Our method allows the artists to simply sketch directly onto the 3D facial model and automatically produces the expeditious manipulation until the desired facial pose is obtained. We show that localized blendshape direct manipulation has the potential to reduce the time-consuming blendshape editing process to an easy freehand stroke drawing.
How to read this
- Category
- Conference paper combining localized blendshape direct manipulation with a sketch interface.
- Contributions
- Localization of direct manipulation using geodesic circles, which confines an edit to nearby geometry.
- A diagnosis that most direct manipulation methods deform globally, which is what makes their results unintuitive.
- A sketch-based interface, modelled on brush painting, layered on top of the localized manipulation.
- The claim that blendshape editing can be reduced to freehand stroke drawing, shown across a range of facial poses.
- Context
- Joins the two threads Cetinaslan had been running separately. The stability work comes from cetinaslan-transposition-blendshape-2017, and the pin-and-drag formulation underneath both comes from lewis-direct-manipulation-blendshapes-2010. The geodesic locality is borrowed from the author's own Verlet framework two years earlier. This is the paper the journal version, cetinaslan-sketching-manipulators-2020, expands.Builds on: Transposition Based Blendshape Direct Manipulation · Direct Manipulation Blendshapes
- Correctness
- Locality is the contribution and also the thing to test: a geodesic radius is a proxy for anatomical influence, and faces do not deform in geodesic circles. The paper shows the proxy works well enough on its examples. What is not shown is behaviour on rigs whose blendshape targets already overlap heavily, where a local edit and a global basis are in tension. Evaluation is by demonstration, no user study.
- Clarity
- Well organised and honest about what it inherits. The brush painting analogy makes the interface easy to picture.
- How to read it
- First pass: abstract, the geodesic circle figure, the pose gallery. Second pass: how the locality term enters the manipulation solve. Third pass: read cetinaslan-sketching-manipulators-2020 instead, which is this paper with more room.
Builds on
Built upon by
Related work
- Sketching Manipulators for Localized Blendshape Editing 2020 / GMOD
- Stabilized blendshape editing using localized Jacobian transpose descent 2020 / GMOD
- Position Manipulation Techniques for Facial Animation 2016 / PhD Thesis
- Sketch-Based Controllers for Blendshape Facial Animation 2015 / Eurographics
Keywords
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