MetaFun - Pragma ADE

13 A few applications
For those who need to be inspired, we will demonstrate how METAPOST can be used to enhance your document
with simple graphics. In these examples we will try to be not too clever, simply because we lack the experience
to be that clever. The real tricks can be found in the files that come with METAPOST.
13.1 Simple drawings
In the words of John Hobby, the creator of METAPOST, “METAPOST is particularly well--suited for
generating figures for technical documents where some aspects of a picture may be controlled
by mathematical or geometrical constraints that are best expressed symbolically. In other words,
METAPOST is not meant to take the place of a freehand drawing tool or even an interactive graphics
editor”.
An example of such a picture is the following one, which is dedicated to David Arnold, who asked
me once how to draw a spring. So, imagine that we want to draw a schematic view of a system of
four springs.
A rather natural way to define such a system is:
z1 = (+2cm,0) ; z2 = (0,+2cm) ;
z3 = (-2cm,0) ; z4 = (0,-2cm) ;
pickup pencircle scaled 1.5pt ;
drawoptions (withcolor .625red) ;
draw spring (z1, z2, .75cm, 2, 10) ; draw z1 -- 1.5 z1 ;
draw spring (z2, z3, .75cm, 2, 9) ; draw z2 -- 1.1 z2 ;
draw spring (z3, z4, .75cm, 2, 8) ; draw z3 -- 1.5 z3 ;
draw spring (z4, z1, .75cm, 2, 7) ; draw z4 -- 1.1 z4 ;
Here, the macro spring takes 5 arguments: two points, the width of the winding, the length of
the connecting pieces, and the number of elements (half windings). The definition of spring is
less complicated than readable.
Simple drawings A few applications
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