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We present a new interactive automatic
skinning method,

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which produces plausible skin elasticity,

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and improves stability over earlier methods such as implicit skinning.

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The new technique also allows for more complex shape motions including large angle joint bends,

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and handle skin contact and muscles bulges.

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Popular approaches like dual quaternion skinning is very fast to compute,

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but it introduces unwanted bulges, self-intersections, and large parametric distortions.

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The recent implicit skinning approach

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fixes the common twisting and bending
artifacts

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while introducing plausible skin contacts in real time.

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Unfortunately, parametric distortions are still evident in extreme bends

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In contrast, our technique twists and bends
robustly 

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while producing skin contacts, controls
parametric distortions,

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and also includes a global elasticity model.

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In all the following results: we use
automatic skinning weights

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computed with heat diffusion.

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We first show dual quaternion skinning with large self-intersecting areas,

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here between the arm the torso.

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Next implicit skinning performs skin contacts,

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but is unable to correct
the skin crease at the shoulders.

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In addition, the effect of skin
elasticity is limited

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and only visible in the upper part of the back.

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Our method avoids the crease and produces the effect of global skin elasticity.

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Notice how the skin moves in the lower part of the back.

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When leaning sideways, dual quaternions exhibit a crease in the torso

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together with an unwanted loss of volume.

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Implicit skinning compensates for this loss,

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but also produces the unwanted crease.

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Our method, automatically distributes the vertices over the implicit skin.

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The crease disappears

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and the global elasticity effect can be seen on the belly.

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Our approach improves stability and
robustness in two ways.

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Firstly, for a large bend,

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dual quaternions typically produce self-intersections.

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Notice how the mesh is stretched at the elbow.

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Implicit skinning is also unable to correct
the meshes distortions,

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and when self-intersections of dual quaternions are too deep,

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the projection on the implicit
surface fails to produce the proper skin contact

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Unlike implicit skinning,

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our method is free from these problems

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 as we don't rely on an initial dual quaternion approximation.

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Secondly, implicit skinning generates
discontinuous gradient in the scalar field

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at the composition stage,

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 this can lead to flickering artifacts seen below the character's breast.

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Our new composition operators produces smooth scalar field

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and avoid this problem.

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Notice also the belly button stretch produced by the global skin elasticity model.

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In the animation of the hand, dual quaternions introduce the self-intersection problem.

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Implicit skinning does not correct this due
to gradient discontinuities in the scalar field.

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Our method doesn't exhibit this creasing or flickering artifacts.

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For detailed characters dual quaternions do not produce plausible results.

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Implicit skinning goes a step further toward
realism,

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but restricts the size of the bending angle due to problems with the generated implicit field.

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Our approach allows large bending angles

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so that an artist using this technique can add primitives

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representing muscles without worrying
about intersection problems.

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In the last example,

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we show the overall robustness of our method

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on a fully skinned armadillo model with a
complex animation.