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Linear blending skinning is popular for its very high performance,

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but is prone to very well known artifacts: such as the loss of volume.

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In addition geometric skinning does not generate contact when the joint bends,

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but rather a smooth fold followed by self intersections.

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Dual Quaternions skinning improve volume preservation,

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but bulges the shape at joints,

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does not generate contact and is also prone to self-intersections.

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In practice we would like a skinning technique to generate contact when joints bend,

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and preserve the rigid appearance articulated bodies in a plausible manner,

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as shown in the video.

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Our implicit skinning technique computed in real time,

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enables interactive deformation while improving the realism of the results

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over real-time state of the art approaches.

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We start with standard inputs: the mesh and its animation skeleton, the skinning weights,

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and the mesh's partition with respect to the skeleton's bones.

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We precompute a field function whose 0.5 iso-surface approximate the mesh part

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associated with each bone, then combined with implicit composition operators

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to define an implicit surface approximating the whole mesh.

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During the animation the mesh is deformed with geometric skinning,

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while the field functions are rigidly transformed.

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The Dual Quaternions solution is corrected by projecting the mesh's vertices

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on the deformed iso-surface following the field function gradients.

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Contact is performed in the folds.

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Our method provide predefined parameters enabling artistic control of the resulting shape.

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In this example we first show how the union operator produces a plausible deformation

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at joints such as: elbows or knees.

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The realism can be enhanced using the predefined gradient-based blending operator

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that keeps the fold surface further from the joint, for large bending angles,

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and produces a small blend for small angles.

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Here again the union operator provides a plausible result.

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A real finger joint generates a fold and contacts surounding by organic bulges.

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This effect can be reproduced using the pre-defined gradient-based bulge-in-contact operator.

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While the automatic settings provided with our method allow us to generate our results,

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it can happen that a complicated joint is inadequatly partitionned.

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A user interaction is then required to add or remove vertices from the set reconstructing the field function.

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This is done with interactive feedback in our system.

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We provide a set of preset parameters.

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These parameters have been set intuitively using the interactive feedback

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provided by our system when their values are modified.

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Here we show the interactive preset of the bulge-in-contact composition operator.

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We now demonstrate the robustness of our method when animating various characters.

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The armadillo model is composed of more than a hundred and seventy thousand vertices.

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The mesh is highly detailed and the joints have features

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that make them very challenging to skin in a acceptable manner.

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The knee is animated and skinned with our method at 36 frame per seconds.

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At extreme postures Dual Quaternions produced deep self-intersections,

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while our method generates the contacts and preserve details.

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We now present several models with complete animations skinned with our method.

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The number of bones and vertices of the models as well as the average frame rates

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are given at the beginning of each animation.

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Each animations includes a comparisons between: our method, Linear Blending and Dual Quaternions.