23 Nov
2007
23 Nov
'07
3:05 a.m.
[...] a spiral that would have 50 dark and light
strips over 3
revolutions. [...] Maybe it could be done with some postscript code
but I'm not sure how.
306 396 translate
0 1 50 {
gsave
dup 21.6 mul rotate
300 -15 moveto 0 0 lineto 300 15 lineto closepath clip newpath
dup 4 mul 50 add
0 0 2 index 350 45 arc
0 0 2 index 10 add 45 350 arcn closepath fill
pop
pop
grestore
} for
newpath
0 0 2 0 360 arc closepath fill
showpage
If everything is right, you'll see the blobs sliding smoothly in or
out, depending on which way it's turning. If the frequency is off,
they'll drift one way or the other circumferentially as well.
Add a line
0 0 moveto 275 0 lineto .05 setlinewidth stroke
just before the "grestore" line and you'll get a starburst of lines for
the blobs to slide along; this may help you detect slight frequency
error - the starburst will drift.
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