       Re: Re: coloring eveerything outside a circle

• To: mathgroup at smc.vnet.net
• Subject: [mg31866] Re: [mg31819] Re: coloring eveerything outside a circle
• From: BobHanlon at aol.com
• Date: Sat, 8 Dec 2001 05:51:41 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```In a message dated 12/5/01 9:55:54 AM, mipam at ibb.net writes:

>> Making something like a black inner tube (whith a white center) is trivial.
>> To do that you show a circle and then a smaller white circle on-top of
>the
>> first circle.  However, it's a little tricky if you want to "see" the
>> graphics behind the center of the inner tube.  Below I show how that
>can be
>> done.
>> --------------------------
>>
>> Block[{\$DisplayFunction=Identity},
>>     gr1=ParametricPlot[ {2*Sin[t], 2*Cos[t]+2}, {t, 0, 2 Pi} ];
>>     gr2=ParametricPlot[ {Sin[t]+1/2, Cos[t]+2}, {t, 0, 2 Pi} ]
>> ];
>>
>> pnts=Join[ Part[gr1,1,1,1,1], Part[gr2,1,1,1,1] ];
>> gr3=Graphics[ { Hue, Polygon[pnts] } ];
>>
>> gr4=Graphics[ { Hue[0.6], Polygon[ {{-2.5,3.75}, {-2.5,3.5}, {3,0.75},
>> {3,1}} ] }];
>>
>> Show[{gr4,gr3}, AspectRatio->Automatic];
>
>Thanks for your answer, but i was looking for something like this:
>
>p1=ParametricPlot[ {Cos[t], Sin[t]}, {t, 0, 2 Pi} ];
>p2=ParametricPlot[ {Cos[t], 0.5+Sin[t]}, {t, 0, 2 Pi} ];
>
>Now, the thing is, i wish to show p2 only for the part which is contained
>inside p1. Normally to do this, i'd have to solve the two corresponding
>equations, equal the y value to Sin[t] for example and find the t and
>draw p2 restricted to those two t value's.
>But .... when you got lets say 20 p's to show and you wish to show only
>those parts which are contained inside p1, you'd have to calculate a lot
>of intersections and then the corresponding t's etc.
>However, i was thinking, why not just draw all these circles
>and paint everything white outside p1 so that it has the same effect.
>It was save mathematica a LOT of calculating time.
>Any ideas?
>Bye,
>
>Mipam.
>
>
>
>

\$Version

"4.1 for Power Macintosh (November 2, 2000)"

Needs["Graphics`Graphics`"];
Needs["Graphics`Colors`"];
Needs["Graphics`InequalityGraphics`"];

DisplayTogether[
Plot[x, {x,0,10}],
InequalityPlot[And[
(x-5)^2+(y-5)^2>9,
(x-5)^2+(y-5)^2<25],
{x, 0, 10}, {y,0,10}],
AspectRatio -> Automatic];

DisplayTogether[
ParametricPlot[
{Cos[t],0.5+Sin[t]},
{t,0,2 Pi}, PlotStyle->Red],
InequalityPlot[And[x^2+y^2>1,
-1< y<2,
-1.5< x<1.5],
{x, -1.5, 1.5}, {y,-1,2},
PlotStyle->White, Fills->White],
Frame -> True, Axes ->False,
AspectRatio -> Automatic];

Bob Hanlon
Chantilly, VA  USA

```

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