       Each  object primitive which can be created in SIPP has an
       argument that describes what kind of  texture  coordinates
       should  be  assigned  to  the  surface of the object. This
       parameter can have one of the following predefined values:

                 o  NATURAL  -  This value tell SIPP to use a two
                 dimensional mapping which is "natural" for  this
                 particular  object. It might be one of the other
                 available mappings  or  it  might  be  something
                 unique  for  the object.  The description of the
                 functions for creating  the  individual  objects
                 specifies how this mapping is done.

                 o  CYLINDRICAL  - A two dimensional mapping. The
                 coordinates are assigned as if the  object  were
                 projected  on  a cylinder surrounding the object
                 and centered on the z-axis object.  The  coordi-
                 nates  are  mapped  so that `x' goes from 0 to 1
                 around the base of the  cylinder  and  `y'  goes
                 from 0 to 1 from bottom to top on it.

                 o  SPHERICAL  -  Same  as `CYLINDRICAL', but the
                 object are projected on a sphere surrounding  it
                 instead.

                 o  WORLD - A three dimensional mapping. The tex-
                 ture coordinates are the same three  dimensional
                 coordinates  as  the  world  coordinates  of the
                 object at creation time.
