egment data obtained by
hidden-line elimination.
The former is faster and the only way for rendered images,
but not suitable for a long animation since it requires much memory
in the X server.
The latter is more memory efficient and suitable for storing data in disks,
but the performance is degraded
when the number of line segments increases.

<P>
In either way, the user provide a function which gives new configurations
to the objects to be drawn and generates drawing on <TT>*viewer*</TT>.
<B>pixmap-animati