Draw dashed lines on TGraph2D

[Wile_E_Coyote]

Try with “cont[0123]z”.
I’m afraid “cont4” is actually a “surf” at theta = 0.
See also:
[Vertical shaded area
[gPad->GetUxmin(),GetUxmax() for 2D histogram
[Drawing a single contour over a TGraph2D using cont4