Hi! How to fix plane position as a 0 degree angle for Phi azimuth angle or how Matlab understand where Phi angle should be drawn?

I have two angles Theta =60 (polar angle which is <=pi) and Phi = 0 ( which is between 0 and 2pi)

I converted spherical coordinates to cartesian and need to draw vector using one point (1.5; 1.5; 3.0) and two angles.

I also use phi =0 to check if my vector correct. Because if phi=0 then my vector will be strict such as on surface of my box. I dont know how to fix one poisition plane as the start point for Phi angle ( where 0 degree of angles will start). My fixed plane position for the begin of Phi angle will be (0,0,3 0,3,3 0,0,0 0,3,0)

something like this but I dont have ro

Answer 1

[Catalytic]

         A = 3.67 * sin(Phi0) * cos(Theta0);
         B = 3.67 * sin(Phi0) * sin(Theta0);
         C = 3.67 * cos(Phi0);

[Aknur]

@Catalytic Thank you

I tried it but it still shows me this one.

If I will accept theta = 0 or phi =0 it is still the same.

I mean that if phi = 0 then the line will lie on the top of the box if theta = 0 then the line will be vertically down.

My angles are: Theta - polar (from 0 to pi) and Phi (azimuth from 0 to 2 pi)

Previous scheme with angles and ro with reverse angels for my case

Could you please suggest another option or what to search? Because I could not understand how Matlab takes a 0 angle. I have edited my question and change the picture. And you can see where will be 0 degrees, 90, 180, 270 degree