## Direct Manipulation of Interactive Character Skins

Alex Mohr, Luke Tokheim, and Michael Gleicher

### Abstract

Geometry deformations for interactive animated characters are most
commonly achieved using a skeleton-driven deformation technique called
linear blend skinning. To deform a vertex, linear blend skinning
computes a weighted average of that vertex rigidly transformed by each
bone that influences it. Authoring a character for linear blend
skinning involves explicitly setting the weights used to compute
deformed vertex positions. This process is tedious, repetitive, and
frustrating not only because the deformed vertex positions are not
intuitively related to the vertex weights, but also because the range
of possible deformations is unclear. In this paper, we present a
method that lets users directly manipulate the deformed vertex
positions in a linear blend skin. We compute the subspace of possible
deformed vertex positions, display it for users, and let them place the
vertex anywhere in this space. Our algorithm then computes the correct
weights automatically. This method lets us provide a skin editing
interface that gives users as much direct control as possible and makes
explicit what deformations are possible.

Here is the pdf Here is
the
accompanying video