mfpic-doc.pdf.

4.2 COMMON OBJECTS. 14
4.2.1 POINTS, LINES, AND RECTANGLES
\point[〈size〉]{〈p 0 〉,〈p 1 〉,...}
Draws small disks centered at the points specified in the list of ordered pairs. The optional
argument 〈size〉 is an absolute dimension that determines the diameter of the disks. The default
is the TEX dimension \pointsize, initially 2pt. The disks have a filled interior if the command
\pointfilltrue has been issued (the initial behavior). After the command \pointfillfalse,
\point commands will produce outlined circles with the interiors erased. The color of the circles
is the value of the predefined variable pointcolor, and the color inside of the open circles is the
value of the variable background. 10
\plotsymbol[〈size〉]{〈symbol〉}{〈p 0 〉,〈p 1 〉,...}
Draws small symbols centered at the points 〈p 0 〉, 〈p 1 〉, and so on. The symbols must be given
by name, and the available symbols are:
Asterisk, Circle, Diamond, Square, Triangle, Star, SolidCircle,
SolidDiamond, SolidSquare, SolidTriangle, SolidStar, Cross, and Plus.
The names should be self-explanatory, the ‘Solid’ ones are filled in, the others are outlines. Under
metapost, symbols are drawn in pointcolor. The 〈size〉 defaults to \pointsize as in \point
above. Asterisk consists of six line segments while Star is the standard five-pointed star formed
from ten straight line segments. Cross is a × shape. The name ‘\plotsymbol’ comes from the fact
that the \plot command (see subsection 4.5.1), which was written first, utilizes these same symbols.
The command \symbol was already taken (standard LATEX).
While one would rarely want to use them for this purpose, the following symbols are also available:
Arrowhead, Crossbar, Leftbar, Rightbar, Lefthook, Righthook, Leftharpoon,
Rightharpoon.
These are mainly intended for making arrows. See subsection 4.4.3 for a further description.
The difference between \pointfillfalse\point and \plotsymbol{Circle} is that the inside
of the circle will not be erased in the second version, so whatever else has already been drawn
in that area will remain visible. This is the default (for backward compatibility), but that can be
changed with the commands below.
\clearsymbols
\noclearsymbols
After the first of these two commands, subsequent \plotsymbol commands will draw the open
symbols with their interiors erased. After the second, the default behavior (described above) will
be restored. These commands have no effect on \point. \plotnodes (see subsection 4.5.1) also
responds to the settings made by these commands. The \plot command (also in subsection 4.5.1)
does not.
You can design your own ‘symbols’. See the discussion of arrowheads in subsection 4.4.3, and
of storing paths in subsection 4.10.2.
\pointdef{〈name〉}(〈xcoord〉,〈ycoord〉)
Defines a symbolic name for an ordered pair and the coordinates it contains. 〈name〉 is any legal
TEX command name without the backslash; 〈xcoord〉 and 〈ycoord〉 are any numbers. For example,
10 METAPOST cannot actually erase. The illusion of erasing is created by painting over with background.