Re: coloring eveerything outside a circle

*To*: mathgroup at smc.vnet.net*Subject*: [mg31819] Re: coloring eveerything outside a circle*From*: Mipam <mipam at ibb.net>*Date*: Wed, 5 Dec 2001 06:51:42 -0500 (EST)*References*: <E1168E31432DD211AF990000F806EFD804E1E720@nems04.nawcad.navy.mil>*Sender*: owner-wri-mathgroup at wolfram.com

> 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[1], 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.