thesis - Computer Graphics Group - Charles University - Univerzita ...

Chapter 1
Introduction
Computer animation of human-like figures has always been an interesting and no doubt challenging
topic pursued by many researchers and computer graphics since the very beginning of
modern computer graphics. The purpose of this work is to get reader acquainted with the theory
of physical-based animation of articulated figures, present the most recent results of the
research in that area and to demonstrate that the technology is ready to be used in the production
environment (animation systems, computer games). To prove this, industry standard
dynamics simulator, capable of running at interactive rates on today’s low-end computers, was
implemented.
The thesis consists of a theoretical part, describing the dynamics theory and some algorithms,
and an implementation part, describing the implementation of the simulator and a figure library
built on top of it. No prior awareness of the theory is required to read this thesis, however basic
knowledge of calculus and linear algebra are demanded.
This chapter provides the reader with a brief information on the character animation background,
gets the reader acquainted with the topics covered by the thesis and its goals. It is relied
upon the reader’s acquaintance with the computer animation basics as we will advance rather
quickly and informally.
1.1 Background
The mere purpose of this section is to identify the context of the area of dynamics discussed
throughout this thesis. We will briefly survey the most commonly used animation techniques of
human-like figures and point out their advantages and disadvantages.
We proceed from the oldest and the most primitive techniques to more advanced ones. Older
techniques are more “low level” as animators have to control every aspect of the produced animation
and their work much resembles the work of traditional animators. While “lower level”
techniques are very close to the raw figure representation (often assorted polygonal mesh), “higher
level” techniques attempt to abstract the figure representation and motion to be generated. Such
techniques are often domain specific (fit for a particular use only) and always use special properties
of the figure to be animated (for example, they are aware of the fact that the figure consists
of a torso, limbs, etc. and take advantage of it).
The most primitive approach, vertex key-framing, treats the whole figure as a polygonal
mesh, where each polygon vertex is animated independently on each other. Animators provide
the animation system with positions of polygon vertices in time (animation curves), defined at
key-frames, and the animation system computes in-between-frames automatically by interpolating
1