In the last years many attempts were taken to simulate lifelike character
behaviour in real-time applications like computer-games.
In a hierarchic organized 3D character, different body parts of the
articulated object are separate objects, stored in a hierarchy and
joined to each other at pivot points, each referencing child objects
(= attached objects of a lower hierarchic order). The flexibility
and adaptability of this method are its main benefits; however this
method also has a number of drawbacks: As the objects in the hierarchy
are all separate, it is inevitable that gaps between these objects
will appear when the character is animated [Lander1997].
Blending between Character Meshes, also called vertex-key-framing,
uses interpolation functions to generate the in-between positions
of the vertices from different poses. Tweening is the fastest way
of animating, but it requires the application to hold multiple copies
of the mesh in memory, one for each key frame, so its memory footprint
is very high. A more flexible solution would allow the artist to set
up the meshes for animation as they normally do, by attaching them
to a skeletal system and then letting the game perform the skeletal
deformation itself. This would enable the application to create unique
animation sequences based on user interaction, instead of interpolating
from pre-modelled and stored poses. Besides offering increased realism,
this technique can be more easily integrated with various physics
simulators.
After taking a look at the requirements of the mentioned animation
techniques, this paper will present an implementation showing the
combination of precomputed animation and real-time effects based on
a skeletal system.