# Datum curves from equations

#### skiddy

##### New member
Is it possible to create a datum curve from equations, that will start and finish at the same point?

But not only exist on the one plane? ( ie i can already create circles etc from equations to exist on any one plane)

#### nkpham

##### New member
i see no problem with starting and ending at the same point. i have tried creating loops in 3d and it works fine. when you enter the make datum curve menu, there is an option called Use Equation. It will ask you to choose a coordinate system as well as a coordinate system type. ( i generally stick to cylindrical type.) the equations you have must be rewritten in terms of the variable t. t's range is from 0 to 1, so if you want this changed, multiply all your t values by the new limit needed. hope this helps.

#### skiddy

##### New member
nkpham,

Can you give me an example of your work with equations that start and finish at the same location that create 3d loops.

I only seem to be able to create one continious curve! But nothing using equations that start and finish at the same point.

Many thanks

#### nkpham

##### New member
try this 2d equation in cylindrical coordinates....

r = sin((5/3) * theta

theta = 720 * t

z = 0

if i find a 3d equation, i'll send it to you.