Re: tracing lines on surface-graphics

*To*: mathgroup at smc.vnet.net*Subject*: [mg25616] Re: [mg25593] tracing lines on surface-graphics*From*: BobHanlon at aol.com*Date*: Mon, 16 Oct 2000 03:04:39 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

In a message dated 10/9/2000 9:58:47 PM, roommate222 at my-deja.com writes: >I can't find an obvious way to trace a line on a surface-graphics >object. I've plotted f(x,y) and got the surface I want, and now I want >to add a curve, say: x varies according to the plotted range, y=1+x/2, >z=f(x,y) --so it lies on the surface I've plotted. I've turned the mesh >off because it's too dense, given the number of points I'm plotting, >but I want to add a couple of such lines - another option would be to >trace every 20th mesh-line or something like that, but that doesn't >seem to be possible either. > Needs["Graphics`Graphics`"]; Needs["Graphics`Graphics3D`"]; plotPts = 41; xMeshSeparation = 1/3; yMeshSeparation = 1/2; xmin = 0; xmax = 6; ymin = 0; ymax = 4; f[x_, y_] := x*y/4; t[x_] := Evaluate[f[x, 1 + x/2]]; mesh = Join[ Table[ScatterPlot3D[Table[{x, y, If[Positive[f[x, y]], 1.01, .99]*f[x, y]}, {y, ymin, ymax, (ymax-ymin)/(plotPts-1)}], PlotJoined -> True, PlotStyle -> AbsoluteThickness[1], DisplayFunction -> Identity], {x, xmin, xmax, xMeshSeparation}], Table[ScatterPlot3D[Table[{x, y, If[Positive[f[x, y]], 1.01, .99]*f[x, y]}, {x, xmin, xmax, (xmax-xmin)/(plotPts-1)}], PlotJoined -> True, DisplayFunction -> Identity], {y, ymin, ymax, yMeshSeparation}]]; trace = ScatterPlot3D[Table[{x, 1+x/2, If[Positive[t[x]], 1.01, .99]*t[x]}, {x, xmin, xmax, (xmax-xmin)/(plotPts-1)}], PlotJoined -> True, PlotStyle -> {AbsoluteThickness[2], RGBColor[1, 0, 0]}, DisplayFunction -> Identity]; surf = Plot3D[f[x, y], {x, 0, xmax}, {y, 0, ymax}, PlotPoints -> plotPts, Mesh -> False, AxesLabel -> {"x", " y", "\n\n\nz "}, DisplayFunction -> Identity, ImageSize -> {430, 350}]; Show[Join[{surf}, {trace}, mesh], DisplayFunction -> $DisplayFunction, ImageSize -> {430, 350}]; Bob Hanlon