Re: Adding markers on the surface of a Plot3D?

*To*: mathgroup at smc.vnet.net*Subject*: [mg89375] Re: Adding markers on the surface of a Plot3D?*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Sat, 7 Jun 2008 03:00:36 -0400 (EDT)*References*: <g2b4o8$nm2$1@smc.vnet.net>

Hi, a) yes you are right, it' cant be done : fun[x_, y_] := Sin[x*y] DynamicModule[{plt}, plt = Plot3D[fun[x, y], {x, -Pi, Pi}, {y, -Pi, Pi}]; Manipulate[ xline = ParametricPlot3D[{x, yc, fun[x, yc]}, {x, -Pi, Pi}]; yline = ParametricPlot3D[{xc, y, fun[xc, y]}, {y, -Pi, Pi}]; Graphics3D[{plt[[1]], Sphere[{xc, yc, fun[xc, yc]}, 0.1], {AbsoluteThickness[4], RGBColor[1, 0, 0], xline[[1]], yline[[1]]}}], {{xc, 0}, -Pi, Pi}, {{yc, 0}, -Pi, Pi} ] ] and an other impossible example fun[x_, y_] := Exp[-x^2 - y^2] DynamicModule[{plt}, plt = Plot3D[fun[x, y], {x, -Pi, Pi}, {y, -Pi, Pi}, PlotStyle -> Opacity[0.5], PlotRange -> All]; Manipulate[ pnt = Append[xy, fun @@ xy]; Graphics3D[{plt[[1]], Line[{Append[xy, 0], pnt}], Sphere[pnt, 0.1], {AbsoluteThickness[4], RGBColor[1, 0, 0], Line[{pnt, pnt*{1, 1, 2}}]}}, PlotRange -> All], {{xy, {0, 0}}, Slider2D} ] ] and Show[] evaluates to a Graphics[]/Graphics3D[] and the FrontEnd show this graphics lik it show you the result of Expand[(x+1)^1000] but in older Mathematica versions the FrontEnd need an other program to display the PostScript and Show[] had a side effect that it paste a rendered image in the Notebook. Regards Jens AES wrote: > I'd like to highlight the two mesh lines that pass through a certain > central point -- let's call it the point {xc,yc} -- on a Plot3D by > thickening those two lines relative to the other mesh lines, or giving > them a distinctive color, or . . . > > Or put a dot on the surface at the point {xc, yc, f[xc,yc]} to identify > this location on the surface . . . > > Or run a vertical "post" up through that point using something like > Line[{xc, yc, 0}, {xc, yc, 2*f[xc,yc]}}] (with the part of the post > below the surface not being seen if you look at the surface from > above) . . . > > I think I've so far tested and confirmed every possible way in which > each of these tasks _can't_ be done . . . > > [And would someone want to help me understand _why_ the > Show[ - - - - -] command (followed by a semicolon) no longer works, or > can no longer be used, as one of a sequence of multiple expressions > within a longer cell? And why it can't even have a semicolon following > it as the last line in a cell? I just can't envision the logic of why > this was a necessary (or optional?) interface design decision -- isn't > Show[---] an expression?] >

**Follow-Ups**:**Re: Re: Re: Adding markers on the surface of a Plot3D?***From:*"peter lindsay" <plindsay@mcs.st-and.ac.uk>

**Re: Re: Adding markers on the surface of a Plot3D?***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>