Re: ParametricPlot3D is buggy

*To*: mathgroup at smc.vnet.net*Subject*: [mg25242] Re: ParametricPlot3D is buggy*From*: "Allan Hayes" <hay at haystack.demon.co.uk>*Date*: Sun, 17 Sep 2000 04:47:20 -0400 (EDT)*References*: <8psgl7$a5r@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Will, You have found a nice bug here - seems to be a fault in calculating the plot range: gr1 = ParametricPlot3D[{Cos[t]Cos[u], Sin[t]Cos[u], Sin[u]}, {t, 0, 2Pi}, {u, -Pi/2, Pi/2}, PlotPoints -> {7, 3}]; PlotRange[gr1] // Chop {{-1.05, 1.05}, {0, 0}, {-1.05, 1.05}} gr2 = ParametricPlot3D[{Cos[t]Cos[u], Sin[t]Cos[u], Sin[u]}, {t, 0, 2Pi}, {u, -Pi/2, Pi/2}, PlotPoints -> {5, 3}]; PlotRange[gr2] // Chop {{0, 0}, {0, 0}, {-1.05, 1.05}} The following work all right. Show[gr1, PlotRange -> All]; Show[gr2, PlotRange -> All]; -- Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565 "Will Self" <wself at msubillings.edu> wrote in message news:8psgl7$a5r at smc.vnet.net... > Can anyone explain this bug that appears in ParametricPlot3D > in my version of Mathematica 4.0.2 on Windows 2000? > > ----------------------------------------------------------- > > This works fine: > > ParametricPlot3D[{Cos[t]Cos[u], Sin[t]Cos[u], Sin[u]}, > {t, 0, 2Pi}, {u, -Pi/2, Pi/2}, PlotPoints -> {8, 3}] > > But this doesn't give a picture: > > ParametricPlot3D[{Cos[t]Cos[u], Sin[t]Cos[u], Sin[u]}, > {t, 0, 2Pi}, {u, -Pi/2, Pi/2}, PlotPoints -> {7, 3}] > > This works fine: > > ParametricPlot3D[{Cos[t]Cos[u], Sin[t]Cos[u], Sin[u]}, > {t, 0, 2Pi}, {u, -Pi/2, Pi/2}, PlotPoints -> {6, 3}] > > But this doesn't give a picture: > > ParametricPlot3D[{Cos[t]Cos[u], Sin[t]Cos[u], Sin[u]}, > {t, 0, 2Pi}, {u, -Pi/2, Pi/2}, PlotPoints -> {5, 3}] > > In this last case, not only do I not get a picture, if I go > back and change the PlotPoints option to anything at all, > in the same cell, I still get no picture. > > With PlotPoints set to {4, 3} I again get no picture, but > surprisingly, with PlotPoings set to {3,3} I get a picture. > Of course in this case the "sphere" has gone flat. > > Do other people experience this same phenomenon? I find it > amazing and frustrating that ordinary things that have been part > of Mathematica for a long time do not work correctly. > > Will Self > > > Sent via Deja.com http://www.deja.com/ > Before you buy. >