NAME
     AddCylinder - add cylinder for schematic drawing

SYNOPSIS
     AddCylinder ( least_square | spacing )

DESCRIPTION
     Add a cylinder that approximates the selected atoms.
     The argument selects between two fit criteria.
     'least_square' does a least square fit of the cylinder
     surface to the atoms, 'spacing' takes the axis
     direction that gives the most regular spacing of
     atoms. The results are normally very similar, but
     'spacing' works better than 'least_square' if very
     few atoms are given.

     A cylinder is added for each molecule that has
     selected atoms. A minimum number of atoms (5 for
     least_square, 4 for spacing) must be selected,
     otherwise the cylinder cannot be determined and an
     error message is issued.

     Cylinders can be used for showing alpha helices in
     schematic drawings. For good results, it is
     recommended to either select the CA or all backbone
     atoms within a helix region.

     The created primitives have the property "cylinder".

EXAMPLE
     AddCylinder spacing

SEE ALSO
     SelectAtom, StyleCylinder, ColorPrim, LengthPrim,
     RemovePrim, AddRibbon, AddSolid, AddDipole

DATE
     970930
