# How to show an angle axis in a RevolutionPlot3D plot

I want to make a RevolutionPlot3D of a three dimensional wave-function which is defined only between two radius. I work in cylindrical coordinates. The idea is to get a plot of the whole region for a given height in the cylinder.

RevolutionPlot3D[ψ3DNorm[1, r, ϕ, 2], {r, 1, 2}, {ϕ, 0, 2 Pi}, PlotRange -> All] I want to be able to keep a track of the angle on the plot by having an axis giving the angle around the plot or at least, a axis stating the angle 0. How can I do that?

• You could try Show[ RevolutionPlot3D[ Cos[4t], {r, 1, 2}, {t, 0, 2 \[Pi]} , AxesOrigin -> {0, 0, 0} , Boxed -> False ] , Graphics3D[{ Thick, Red, Arrow[{{0, 0, 0}, {0, 2, 0}}] }] ]. You can obviously add more complex graphics this way as well. – N.J.Evans Jun 6 '16 at 15:31
• Thank you but with that solution, you don't have a clue about the direction of rotation in which the angle is plotted by the function? – Ezareth Jun 6 '16 at 18:43
• Why not use something like Hue[] to color your surface according to the angle of interest instead? – J. M. will be back soon Jun 7 '16 at 17:05

Perhaps you could color-code some custom mesh lines to indicate the angular values at that position:

plot = RevolutionPlot3D[
Cos[4 t], {r, 1, 2}, {t, 0, 2 Pi},
Mesh -> {{
{1*^-6, Directive[Black, Thick]},
{Pi/2, Directive[Red, Thick]},
{Pi, Directive[Darker@Green, Thick]},
{3/2 Pi, Directive[Blue, Thick]}}
},
MeshFunctions -> {Function[{x, y, z, t, theta, r}, theta]},
ImageSize -> Large
] The black line corresponds to $\theta = 0$, the red line to $\theta = \pi/2$, and so on.

(Note that I had to shift the first mesh line slightly away from $0$ because otherwise it would have been overshadowed by a thing gray line at that position, whose origin is unclear to me.)

• I would guess that the gray line you got came from BoundaryStyle. Try setting it to None. – J. M. will be back soon Jun 7 '16 at 17:04
• @J.M. I should have been more clear. I had in fact tried to set BoundaryStyle -> None, which indeed removes the grey "mesh line" at $0$ as well as the boundary line, but even then no custom mesh line is shown at the $0$ position: code&result. I have also tried machine-precision 0. instead, with no luck. I'll dig into older questions later today; perhaps this is a known issue? – MarcoB Jun 7 '16 at 17:09
• Hmm, I think that would be due to roundoff error, so that the $\theta$ mesh doesn't actually start at $0$. I believe this problem has indeed been encountered before here, but I can't find relevant threads at the moment. – J. M. will be back soon Jun 7 '16 at 17:21