creating slides
There are a number of contexts, and associated file types,
in which slides may be created:
- .t -- the ultimately generic format, uses all filters
- .tm -- limited .t format with VRML support, uses ht-ml.flt + vr-ml.flt
- .pvl -- VRML slides support, uses vr-ml.flt -pvl
- .es -- for the use of slides in worlds
See example makefiles for actual usage