试过用Densityplot画2D隐函数没问题，但是3D的为啥就不行了，求指教，代码贴下面：
m = -1;
\[Lambda] = 0.785;
k = 2*Pi/\[Lambda];
r0 = 30;
r[x_, y_] := (x^2 + y^2)^(1/2);
\[Psi][x_, y_] := ArcTan[x, y]
data2 = Table[\[Psi][x, y], {x, -20, 20, 0.1}, {y, -20, 20, 0.1}];
ListDensityPlot[data2]
mycolor[a_] := Blend[{Black, Gray}, a];
DensityPlot3D[
Cos[(Abs[m] + 1) (\[Pi]/2 - ArcTan[(k r[x, y])/(2 z)]) - (
k (r[x, y])^2)/(2 (z + (k^2 (r[x, y])^4)/(4 z))) -
m \[Psi][x, y] - k z] == 1, {x, -20, 20}, {y, -20, 20}, {z, 0,
10 \[Lambda]}, PlotRange -> All]