mfpic-doc.pdf.

4.11 PARAMETERS. 60
(notably those that set the axismargins and \tlabel parameters) change both TEX parameters and
METAFONT parameters, and it is important to keep them consistent.
There are a few parameters that do obey TEX grouping, but only inside mfpic environments.
These are noted where the parameter is described.
All parameters are initialized when MFPIC is loaded. We give the initial value or state in each of
these descriptions.
\mfpicunit
This dimension stores the basic unit length for MFPIC pictures. The x and y scales in the \mfpic
macro are multiples of this unit. The initial value is 1pt. It is global outside an mfpic environment.
Changes made to it inside an mfpic environment have no effect and are lost at the end of the
environment.
\pointsize
This dimension stores the diameter of the circle drawn by the \point macro and the diameter
of the symbols drawn by \plot, \plotsymbol and \plotnodes. The initial value is 2pt.
\pointfilltrue, \pointfillfalse
This TEX boolean switch determines whether the circle drawn by \point will be filled or open
(outline drawn, inside erased). The initial state is true: filled. This value is local to any TEX group
inside an mfpic environment. Outside such it is global.
\pen{〈size〉}
\drawpen{〈size〉}
\penwd{〈size〉}
These commands establishes the width of the normal drawing pen (that is, the thickness of lines,
whether solid or dashed). The initial value is 0.5bp. This width is stored by METAFONT. This has
no effect on the size of dots for \dotted, \shade, \grid, etc. It also has no effect on the lines
drawn for hatching. There exist three aliases for this command, the first two to maintain backward
compatibility, the last one for consistency with other dimension changing commands. Publishers
generally recommended authors to use at least a width of one-half point for drawings submitted for
publication.
\shadewd{〈diam〉}
This command sets the diameter of the dots used in the shading macro. The drawing and hatching
pens are unaffected by this. The initial value is 0.5bp, and the value is stored by METAFONT.
\hatchwd{〈size〉}
This sets the line thickness used in the hatching macros. The drawing pen and shading dots are
unaffected by this. The initial value is 0.5bp, and the value is stored by METAFONT.
\polkadotwd{〈diam〉}
This sets the diameter of the dots used in the \polkadot macro. The initial value is 5bp, and the
value is stored by METAFONT.
\headlen
This dimension stores the length of the arrowhead drawn by the \arrow macro. The initial value
is 3pt.