Database Reference
In-Depth Information
Figure 8: Motion ptterns — Composed measure structures
•
Measure 5:
random structure
. This structure should be regarded as a composed
measure only if it appears several times in the “motion text”; otherwise it should be
regarded as a quasi measure.
An elementary measure is an ordered vector, made of repeated identical bit fi les. A
composed measure is an ordered matrix, in which the matrix rows are elementary measures.
The number of matrix rows is equal to the number of relevant links, and the length of the
elementary measure is according to the lowest “common denominator”.
STORAGE COMPARISON
To learn more about motion storage and performance, we conducted several compari-
sons between our binary model and a common system. Life Forms, a desktop application
developed at Simon Fraser University (Calvert, Bruderlin, Dill, Schiphorst & Welman, 1993),
is a representative system based on the key frames approach. A collection of convenient
tools for the development of multiple human fi gure animation, it runs on platforms ranging
from a low-end Macintosh up to a high-end Silicon Graphics Iris.
The Key Frames Approach
In the key frames approach, motion is represented by the absolute
position
of every
limb while in the binary model storage is based on the internal geometric
relations
between
the creature
links
, i.e., on
relative changes
. Position in our model is a derivative of motion.
This difference is more than conceptual; it affects storage in terms of data redundancy, as
described below.
Movement and Dragging
The key frames approach does not distinguish between movement and dragging. Drag-
ging occurs when a given limb changes its location in space; i.e., it is a change in position,
without changing the internal geometric relation with adjacent links. Consider for example
