Do btex labels work?
Not here. btex … etex runs TeX as a second program, which the sandbox does not allow. Plain string labels such as label("A", z) and defaultfont text work.
Tools · MetaPost
Online MetaPost editor
Write a MetaPost figure between beginfig and endfig and get it drawn without a TeX installation. Loops, recursive macros and exact geometry all work; download it as SVG or PNG.
See the examplesHave Forma write one
Or describe it in words and get source you can edit, checked before you see it.
Part of Forma Visuals: Draw a technical or research figure · Draw a geometry figure
⌘ or Ctrl + Enter draws. Sent to Forma's renderer, which keeps nothing
loadingStarting the renderer…
Koch snowflake A recursive macro replaces every edge with four edges a third as long, four levels deep: a finite area inside an ever longer perimeter.
In your browser, drawn with Plotly.js (MIT), Apache ECharts (Apache-2.0, notice), Chart.js (MIT).
01 Examples
MetaPost examples to start from.
Koch snowflake
A recursive macro replaces every edge with four edges a third as long, four levels deep: a finite area inside an ever longer perimeter.
Source
% The Koch snowflake: each edge replaced by four edges a third as long,
% four times over. Finite area, but a perimeter that grows without bound.
vardef koch(expr a, b, n) =
if n = 0: a -- b
else:
save p, q, r; pair p, q, r;
p := a + (b - a) / 3;
r := a + 2(b - a) / 3;
q := p + ((r - p) rotated 60);
koch(a, p, n - 1) & koch(p, q, n - 1) & koch(q, r, n - 1) & koch(r, b, n - 1)
fi
enddef;
beginfig(1);
pair A, B, C; A := (0,0); B := (6cm,0); C := A + ((B - A) rotated 60);
path flake; flake := koch(A, C, 4) & koch(C, B, 4) & koch(B, A, 4) -- cycle;
fill flake withcolor (0.86,0.93,1);
draw flake withpen pencircle scaled 0.4pt withcolor (0.15,0.35,0.7);
endfig;
end
Function graph with axes
y = 1.6√x on arrowed axes with tick marks and numbers placed by for loops, the curve joined smoothly through sampled points, and one point marked and labelled.
Source
beginfig(1);
u := 1cm;
% axes with arrowheads
drawarrow (-0.5u, 0) -- (6.5u, 0);
drawarrow (0, -0.5u) -- (0, 4.5u);
label.bot("x", (6.5u, 0));
label.lft("y", (0, 4.5u));
% tick marks and numbers from a loop
for i = 1 upto 6:
draw (i*u, -2pt) -- (i*u, 2pt);
label.bot(decimal i, (i*u, -2pt));
endfor
for j = 1 upto 4:
draw (-2pt, j*u) -- (2pt, j*u);
label.lft(decimal j, (-2pt, j*u));
endfor
% y = sqrt(x) * 1.6, joined smoothly through sampled points
path p;
p := (0, 0) for x = 0.25 step 0.25 until 6: .. (x*u, 1.6*sqrt(x)*u) endfor;
pickup pencircle scaled 1.2pt;
draw p withcolor (0.1, 0.3, 0.7);
% mark and label one point on the curve
z1 = (4u, 3.2u);
draw (4u, 0) -- z1 -- (0, 3.2u) dashed evenly withcolor 0.6white;
pickup pencircle scaled 4pt;
drawdot z1 withcolor (0.8, 0.1, 0.1);
label.ulft("(4, 3.2)", z1);
label.rt("y = 1.6 sqrt(x)", (0.6u, 3.8u)) withcolor (0.1, 0.3, 0.7);
endfig;
end
Pythagoras' theorem
A 3-4-5 right triangle with a square on each side, where 9 plus 16 makes 25, drawn with MetaPost pairs and rotations.
Source
beginfig(1);
% a right triangle with the square on each side: a*a + b*b = c*c
u := 6mm;
pair A, B, C; A := (0,0); B := (4u,0); C := (0,3u);
pair n; n := (C - B) rotated -90;
fill A -- B -- B + (0,-4u) -- A + (0,-4u) -- cycle withcolor (0.85,0.9,1);
fill A -- C -- C + (-3u,0) -- A + (-3u,0) -- cycle withcolor (1,0.88,0.85);
fill B -- C -- C + n -- B + n -- cycle withcolor (0.86,0.95,0.86);
draw A -- B -- C -- cycle withpen pencircle scaled 1pt;
draw A -- B -- B + (0,-4u) -- A + (0,-4u) -- cycle;
draw A -- C -- C + (-3u,0) -- A + (-3u,0) -- cycle;
draw B -- C -- C + n -- B + n -- cycle;
label("16", A + (2u, -2u));
label("9", A + (-1.5u, 1.5u));
label("25", 0.5[B, C] + 0.5n);
label.top("4", 0.5[A, B]);
label.rt("3", 0.5[A, C]);
label.llft("5", 0.5[B, C]);
endfig;
end
Clock face
Sixty ticks and twelve numbers placed by a loop using polar directions, with the hands at ten past ten, the time watchmakers like to show.
Source
beginfig(1);
r := 2cm;
draw fullcircle scaled 2r withpen pencircle scaled 1.2pt;
for i = 0 upto 59:
if i mod 5 = 0:
draw (dir (90 - 6i)) scaled 0.86r -- (dir (90 - 6i)) scaled r withpen pencircle scaled 1.2pt;
label(decimal (if i = 0: 12 else: i div 5 fi), (dir (90 - 6i)) scaled 0.72r);
else:
draw (dir (90 - 6i)) scaled 0.94r -- (dir (90 - 6i)) scaled r;
fi
endfor;
% ten past ten, the watchmaker's favourite time
draw origin -- (dir (90 - 305)) scaled 0.5r withpen pencircle scaled 2.4pt;
draw origin -- (dir (90 - 60)) scaled 0.8r withpen pencircle scaled 1.4pt;
fill fullcircle scaled 4pt;
endfig;
end02 About MetaPost
What MetaPost is good for.
MetaPost is John Hobby's language for technical drawings, descended from Knuth's METAFONT. You state equations and paths and it solves for the points, which makes precise geometry, loops of repeated shapes and recursive figures short to write.
What must the source contain?
At least one beginfig … endfig, and end at the close. The first figure is the one drawn.
Can a figure read files?
No. The renderer runs in a sandbox with no access to files outside its own folder and no network, and nothing you send is kept.