Re: Model the surface of an ellipsoid

*To*: mathgroup at smc.vnet.net*Subject*: [mg93623] Re: Model the surface of an ellipsoid*From*: Mayneord <xrayspectrum at googlemail.com>*Date*: Tue, 18 Nov 2008 07:22:08 -0500 (EST)*References*: <gfgqib$dm1$1@smc.vnet.net> <gfh3ca$g1d$1@smc.vnet.net>

On Nov 14, 12:36 pm, Jens-Peer Kuska <ku... at informatik.uni-leipzig.de> wrote: > Hi, > > after simple algebra you end up with > > R^2 == r^2 + R^2*d^2/D^2 > > and since you have 4 variables, you > can fix one of the variables > > With[{D = 1}, > ContourPlot3D[ > R^2 == r^2 + R^2*d^2/D^2, {r, -2, 2}, {R, -2, 2}, {d, -2, 2}]] > > or make an interactive version. > > Manipulate[ > ContourPlot3D[ > R^2 == r^2 + R^2*d^2/D^2, {r, -2, 2}, {R, -2, 2}, {d, -2, > 2}], {D, -2, 2}] > > Regards > Jens > > Mayneord wrote: > > On Nov 13, 12:34 pm, Jens-Peer Kuska <ku... at informatik.uni-leipzig.de> > > wrote: > >> Hi, > > >> and > > >>http://mathworld.wolfram.com/Ellipsoid.html > > >> has no parametric or implicit equation for you ? > >> And you can't even download the notebookhttp://mathworld.wolfram.com/n= ote= > > books/Surfaces/Ellipsoid.nb > >> ?? > >> Too bad > > >> Regards > >> Jens > > > Hi Jens, > > > Thank you so much for your reply. > > when i wrote this post, I was sure that i will get a reply from you > > first ;-) > > > I already download the notebook long ago. > > I did not understand anything from that it seems to be too much of > > mathematics to me. > > In my case i have only 4 unknown parameters ( 1 = Sqrt[r^2/R^2 + d^2/ > > D^2] ). Typically, also shown in the websitehttp://mathworld.wolfram.co= m/El= > > lipsoid.html, > > for a ellipsoidal there must at least three coordinates. But the > > equation which is i have seems to be different. please tell me if am > > wrong. Please understand i am using mathematica 5.2. > > > I used an ImplicitPlot like this i get only 2D plot. > > ImplicitPlot[Sqrt[(x^2/9) + (y^2/4)] == 1, {x, -3, 3}] > > > My question is for 3D it is more complicated? do i need to use much > > of trigonometry for the angles? > > > thanks again > > > May Hi Jens, Thanks a lot for you help! With ContourPlot3D it was very simple to model the whole volume of the ellipse. Thanks again ! With Regards, Mayneord.