Game Development Reference
In-Depth Information
-13-
Layered Skin Simulation
Kiaran Ritchie
13.1
Introduction
This article proposes a multilayered, artist-controlled, modular approach to the
problem of creating believable mesh-based skin deformations. The general idea
is to create a chain of layered deformations, the result of which approximates
the behavior of skin. It is well known that traditional smooth skinning produces
unsightly artifacts and fails to capture the full range of desired effects, namely,
skin sliding, volume preservation, and jiggling.
To fix this, volume preservation is enforced as a postprocess by forcing colli-
sion between the deformed skin and an artist-built underlying polygonal anatomy
using an optimized ray-casting technique. The resulting mesh is passed to a relax-
ation phase that enforces an elastic behavior using a modified Jakobsen constraint
solver. The relaxed vertex positions are sent to the final phase, where a jiggle ef-
fect is added to the skin. This phase computes a per-vertex force vector and uses
a simple Euler-integration step to provide some temporal coherence.
I will show that a layered combination of simple modules is sufficient in re-
producing the macroscale volume changes observed in moving creatures. Due to
the rapid advancement of many-core CPU/GPGPU architectures, these techniques
will soon be applicable to real-time environments. It is encouraging that these al-
gorithms are simple to implement, intuitive to work with, and trivially optimized
for parallel processors.
13.2
Layered Deformation Architecture
In this article, I would like to introduce physics and animation programmers to
the concept of layered deformations. The aim of this section is to convince you
that a slight shift in the way we organize our deformation pipelines could usher
in a floodgate of much-needed improvements in the fidelity of real-time character
animation.
 
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