Implicit skinning

Abstract

a) (b) Linear blending (c) Our with contact (d) Our with bulge (e) Real finger Figure 1: (a) Real-time animation of the index finger of a hand model composed of 31750 vertices. Two poses are shown in each column: (b) standard smooth skinning with linear blending at 95 frames per second (fps), (c) our method which compensates the loss of volume on top of joints and models contact in the fold at 37 fps, (d) our method with an additional bulge mimicking tissues inflation at 35 fps, and (e) a picture of a real bent finger. AbstractGeometric skinning techniques, such as smooth blending or dualquaternions, are very popular in the industry for their high performances, but fail to mimic realistic deformations. Other methods make use of physical simulation or control volume to better capture the skin behavior, yet they cannot deliver real-time feedback. In this paper, we present the first purely geometric method handling skin contact effects and muscular bulges in real-time. The insight is to exploit the advanced composition mechanism of volumetric, implicit representations for correcting the results of geometric skinning techniques. The mesh is first approximated by a set of implicit surfaces. At each animation step, these surfaces are combined in real-time and used to adjust the position of mesh vertices, starting from their smooth skinning position. This deformation step is done without any loss of detail and seamlessly handles contacts between skin parts. As it acts as a post-process, our method fits well into the standard animation pipeline. Moreover, it requires no intensive computation step such as collision detection, and therefore provides real-time performances.

Dynamic implicit muscles for character skinning

“…This segmentation associates a part defined by a set of mesh vertices to each bone, each of them representing an articulated body part( finger phalanx, upper and lower arm, thigh, leg, torso, etc.). In Implicit Skinning, each part is approximated with an isosurface in a 3D scalar field with compact support f j : R 3 → R. Vaillant et al [7] use Hermite-Radial-Basis-Functions (HRBF) [62] to define these scalar fields f j for their natural ability to approximate positions and normals with smooth scalar fields. Following the standard convention used in compact support implicit surface modeling [63], the approximating isosurface of f j is the 0.5-isosurface.…”

“…Implicit Skinning relies on compactly supported field functions and an homogeneous formulation is required to adequately integrate our functions [63]. We thus convert our muscles to compact support by composing f M with a fall-off transfer function as done for the HRBF fields described by Vaillant et al [7]. We then assemble together all muscular fields associated with a given animation bone with a union operator before blending them with the HRBF to produce the new fields f j .…”

“…Our contribution is an approach that combines the advantages of muscle primitive deformers with an interactive geometric skinning technique producing high-quality skin deformation including contact handling ( Figure 1). We rely on Implicit Skinning [7,8] to resolve self-intersections and represent skin elasticity. However, unlike Implicit Skinning, in this paper we also consider several important phenomena contributing to muscle and skin shape, such as muscle-muscle and muscle-bone collisions and dynamic effects induced by the skeletal motion.…”

N-ary implicit blends with topology control

“…Skeleton-based implicit surfaces, built by blending primitive shapes, where introduced as an easy way to model complex and dynamic topology [2,3]. They have been used since then for rendering water and viscous material [4,5,6], for combining shape components in sketch-based modeling applications [7], for animating garment folds that merge rather than collide [1] and recently, for improving character skinning [8].…”

Surface deformation over flexible joints using spline blending techniques

“…However, the dual quaternions method is unable to produce realistic musculature and dynamics effects [8]. In recent years new ways and methods have been proposed, including the volume preserving method implicit skinning [10].…”