Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!uxc.cso.uiuc.edu!garcon!altair!george
From: george@altair (John George)
Newsgroups: comp.graphics
Subject: Re: Mathematica
Summary: Here's a toy.  Enjoy.
Message-ID: <1868@garcon.cso.uiuc.edu>
Date: 28 Aug 89 15:29:47 GMT
References: <58589@tut.cis.ohio-state.edu>
Reply-To: george@symcom.math.uiuc.edu (John George)
Organization: Dept. of Mathematics, Univ. of Illinois at Urbana-Champaign
Lines: 31

In article <58589@tut.cis.ohio-state.edu> <ray@cis.ohio-state.edu> writes:
>(hope both these newsgroups are appropriate here)
>
>does anyone know what it's good for?  (Ok I can read the instructions,
>anyone have any novel ideas, interesting custom packages, hints & tips, 
			      ^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
>Thanx
>Will Ray

 spirograph[p_Integer, q_Integer, a_, start_:0, opts___Rule] :=
	Block[ {m = (q-p)/q, n = (q-p)/p, x = Cos[start], y = Sin[start]},
        ParametricPlot[{
			x(m Cos[t] + a Cos[n t]) - y(m Sin[t] - a Sin[n t]),
        		y(m Cos[t] + a Cos[n t]) + x(m Sin[t] - a Sin[n t])
			},
        {t, 0, 2 p Pi}, opts, AspectRatio -> Automatic,
        PlotPoints -> 24, Axes->None]
	];
spirograph::usage="spirograph[p, q, a, rot:0, (optionlist)]
displays the spirograph design formed by an outer wheel of
radius one and an inner wheel of radius p/q, with a pen placed 
a units from the center; beginning at start radians above the 
x-axis.";
Null;

Try something like, spirograph[2, 3, .1]; spirograph[2, 3, .15];
and then Show[ %<line number of first output>, %<line number of second output>].
The latter command writes one design over the other.

--John C. George