@anhnha What part of the plot is it that troubles you?

@C.E. what function should I use?

I tried ParametricPlot3D

but couldn't make it

@anhnha Could you show the code?

that works!

now I'll need to try with the projector

@anhnha What is your plan for how to do that?

They're 2D functions so I'm thinking how to plot 2D in 3D

@anhnha Consider using Plot3D with a function like this: {1, y, f[z]}, e.g. one component is constant.

ops, Plot3D does not accept that type of argument. Well, tell me if you need help.

@C.E. so how would you add the real and imaginary functions on the plot generated by that ParametricPlot3D?

@anhnha My idea is the same as before, it's just that I said Plot3D instead of ParametricPlot3D:

ParametricPlot3D[{
  {t, Cos[2 Pi t], Sin[2 Pi t]},
  {t, Cos[2 Pi t], -2},
  {t, 2, Sin[2 Pi t]}
  },
 {t, 0, 3},
 PlotRange -> {{0, 3}, {-2, 2}, {-2, 2}}
 ]

I see. is there a simple way to know which axis is which?

Also how can I add grid in each side?

@anhnha Did you look in the documentation and did anything seem relevant?

f.e. FaceGrids:

FaceGrids -> {{-1, 0, 0}, {0, 1, 0}, {0, 0, -1}},
Boxed -> False

As to how to tell which axis is which, there are lots of ways. You can tell be the direction in which the curve is travelling, you can tell by the coloring of the curves (in the order blue, orange, green), you could use plot labels to labels the axes etc.

The first method to determine axis is really hard

how do you check the color to know the axis?

Just make a couple of plots and see what the default colors are for the first, second, and third plot. Then see where those colors end up in your 3D plot.

Or otherwise, just look what the curves look like. One is a sin curve, the other one is a cosine. Like I said, lots of ways.

Curve lines are not good because sometimes you don't know what curve is which

Can anybody test if the following is fixed in v12 desktop?: mathematica.stackexchange.com/q/21826/1871

not yet

@anhnha Thx. What's somewhat funny is, it's fixed on Cloud.

"12.0.0 for Microsoft Windows (64-bit) (April 6, 2019)"

@xzczd Also an issue in the prerelease.

@CarlLange Aha

@anhnha Of course you do, if you plot ParametricPlot3D[{f1, f2, f3}, ...] then you know that f1 will be colored blue, f2 will be colored orange, and f3 will be colored green. But if you don't like that, why don't you add labels like I suggested?

AxesLabel -> {"X", "Y", "Z"}

@C.E. I also use label

@anhnha @xzczd @CarlLange Some else had to point me to my own answer about this :)

And it is indeed a bug that is very very old.