NAME
     AddSheet - add sheet for schematic drawing

SYNOPSIS
     AddSheet

DESCRIPTION
     Create a surface that serves as schematic drawing of
     a beta sheet. The surface will approximate all
     selected atoms that belong to the same sheet. An atom
     is considered belonging to a sheet if the residue it
     belongs to has the 'sheet' property set. Even if
     multiple atoms of one residue are selected, only one
     of them is taken for determining the surface, it is
     recommended to select just the CA atoms.

     The surface will not exactly pass through the atoms,
     but a smoothing algorithm is applied. To get nice
     smoothing at the borders, it is good to select not
     just the sheet atoms, but also atoms that are adjacent
     to the sheet.

     The command is very easy to use for structures that
     have just one beta sheet. Then the user can just
     select all CA atoms and execute the command, provided
     that the secondary structure is known from the PDB
     file or calculated using the CalcSecondary command.

     If a structure has multiple beta sheets, they have to
     be created one after the other. It is best to start
     with all CA selected, create one sheet, deselect the
     atoms belonging to that sheet, creating the second
     sheet, etc.

     The created primitives have the property "sheet".

EXAMPLE
     AddSheet

SEE ALSO
     ReadPdb, CalcSecondary, SelectAtom, DefPropRes,
     AddRibbon, ColorPrim, TintPrim, ShadePrim,
     RemovePrim

DATE
     970723
