RE: ParamtricPlot3D

*To*: mathgroup at smc.vnet.net*Subject*: [mg32130] RE: [mg32119] ParamtricPlot3D*From*: "David Park" <djmp at earthlink.net>*Date*: Sat, 29 Dec 2001 00:46:50 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Erich, You are double covering the sphere because you are using too wide a domain for the v variable. Try ParametricPlot3D[{Sin[u]*Cos[v], Cos[u]*Cos[v], Sin[v]}, {u, -Pi, Pi}, {v, -Pi/2, Pi/2}]; Because of the approximate nature of the calculations, Mathematica obtains interweaved surfaces which it has a very difficult time in rendering. In general with 3D graphics in Mathematica it is best to avoid unnecessarily interweaved surfaces. David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ > From: Erich Neuwirth [mailto:erich.neuwirth at univie.ac.at] To: mathgroup at smc.vnet.net > > when displaying s sphere with > > ParametricPlot3D[{Sin[u]*Cos[v],Cos[u]*Cos[v],Sin[v]},{u,-Pi,Pi},{ > v,-Pi,Pi}] > > the resultig display does NOT have a convex surface. > > and so does > ParametricPlot3D[{Sin[u]*Sin[v],Cos[u]*Sin[v],Cos[v]},{u,-Pi,Pi},{ > v,-Pi,Pi}] > > in the second case, in the horizontal crosscuts > ther points go "in and out", one is close, ons is farther next is closer > ... > to the center. > > since i want to create 3d objects in other programs, > this is not good. > > setting PlotPoints higher > does not completely solve the problem. > is there an easy solution? > > -- > Erich Neuwirth, Computer Supported Didactics Working Group > Visit our SunSITE at http://sunsite.univie.ac.at > Phone: +43-1-4277-38624 Fax: +43-1-4277-9386 >