mfpic-doc.pdf.

4.12 FOR ADVANCED USERS. 64
\cbclosed...
\qbclosed...
These are modifying macros that close the following path. The first closes with a cubic B-spline,
the second with a quadratic B-spline. They will close any given curve, but the command \cbclosed
is meant to close a cubic B-spline (see above). That is, \cbclosed\cspline should produce the
same result as \closedcspline with the same argument. The corresponding statements are true of
\qbclosed: it is meant to close a quadratic B-spline and \qbclosed\qspline should produce the
same result as \closedqspline with the same argument.
4.12.2 BÉZIERS
The power user, having noticed that \curve and \cyclic insert some direction modifiers into the
path created, may have decided that there is no MFPIC command to create a simple METAFONT
default style path, for example (1,1)..(0,1)..(0,0)..cycle. If so, he or she has forgotten about
\mfobj: the command
\mfobj{(1,1)..(0,1)..(0,0)..cycle}
will produce, in the .mf file, exactly this path, but surround it with the TEX wrapping needed to
make MFPIC’s prefix macro system work. However, the syntax of more complicated paths can be
extremely lengthy, so we offer this interface:
\mfbezier[〈tens〉]{〈list〉}
\closedmfbezier[〈tens〉]{〈list〉}
These figure macros uses the METAFONT path join operator ‘..tension 〈tens〉..’ to connect
the points in the list. If the tension option [〈tens〉] is omitted, the value set by \settension (initially
1) is used. One can get a cyclic path by prepending \bclosed (with matching tension option),
but it will not produce the same result as \closedmfbezier. These are cubic Bézier’s (but you
know that if you are a power user). Quadratic Béziers (as in LATEX’s picture environment) can be
obtained with the following:
\qbeziers{〈list〉}
\closedqbeziers{〈list〉}
These figure macros produce quadratic Bézier curves, the equivalent of a sequence of LATEX
\qbezier commands. Note the plural forms, to distinguish the first from the LATEX command, and
to indicate that they can draw a series of quadratic Béziers.
In the 〈list〉, the first, third, fifth, etc., are the points to connect, while the second, fourth, etc., are
the control points. The open version requires an ending point, and so needs an odd number of points
in the list. The closed version assumes the first point is the ending, and so requires an even number
in the list. If the number of ponts is wrong, no error is produced: the last point is simply repeated to
get the required number.
The curve will not automatically be smooth; that depends on the choice of the control points.
\cbeziers{〈list〉}
\closedcbeziers{〈list〉}
These figure macros produce a series of cubic Bézier curves. In the 〈list〉, the first, fourth, seventh,
etc., are the points to connect, while the second and third, fifth and sixth, etc., are pairs of
control points. The closed version uses the starting point as the ending point, and so needs a number
of points divisible by 3 (n = 3k). The open version requires an explicitly given ending node (so
n = 3k + 1). If the number of ponts is wrong, no error is produced: the last point or last two points
are simply repeated to get the required number.