doubl.fig

animation created with the following code, then captured with recordmydesktop. code is licensed cc0, video is also licensed cc0.

#### license: creative commons cc0 1.0 (public domain)
#### http://creativecommons.org/publicdomain/zero/1.0/
proginf = "doublespiral 2017 mn"
function rgbcolour r g b c
python
figcgapal[c] = (r, g, b)
fig
fig
now lineinput
v 1
c 400
w 3.14159 divby 2
for r 490 300 -.25
e w minus 0.00413367105263 swap e w # 3.14159 / 4 / (490 - 300)
for p -3.14159 3.14159 .003067958984375
e w cos times 380 divby 2 int
rc r divby 2 int
rd 256 minus rc rgbcolour rc rc rc 11
x p times 2 cos times e plus c int
y p times 2 sin times e plus r minus 50 int
m 6.28 plus 1.57 divby 108.503 divby 2
now v plus m swap now v
rc r divby 4 int mod 2
iftrue rc
now v int mod 2 times 11 pset x y now
y2 y minus 1 pset x y2 now
fig
next
now display
next
now display lineinput