Polar vase

I thought this would be a nice way to demonstrate polar graphs to my kids. [Desmos](https://www.desmos.com/calculator) makes graphing polar coordinates ridiculously easy. Add a variable that creates a nice 3d printable transition

Make a nice graph. Then add a variable (ie 'j' or 'k') that creates a nice 3d printable transition.
Copy this as a new function in the openscad file:


function newpolarfunction(z,t) =
let(tt = z % 2 == 0 ? t*tstep : (t+shift)*tstep,
j = * z/zmax - , k= ,
rr = * ) )
[rr*cos(tt),rr*sin(tt),z*zstep];


Comment out the current function at line 106 and add the "newpolarfunction(z,t)"