# 2 Projections

#### nkpham

##### New member
I need to create a 3d datum curve, but one of my curves is created through an equation. Before, I just used a 2 Projection datum curve and sketched the independent curves to form the 3d curve. I can't figure out how to do this with equations instead. When I use this 2 projection feature, it automatically asks me to pick a sketching plane and there is no option for an equation. Does anyone know how to do this?

#### xcad

##### Member
A 2 projection curve needs two 2D curves, so to be created from the projection of them. So If your equation curve is 2D, just sketch the curves by equation first (be carefull the planes that the curves is to be created) and then with the Use Edge option select this curve for the creation of the projection curve.

If your equation curve is 3D, is a projection curve itself.

So if you use this curve, for one of the two curves), you will get its projection to the plane you select to sketch the curve , so you come up to false results.

xcad

#### nkpham

##### New member
I am making two 2D projections to create a 3D curve. After I create the first curve using the equation feature, where do I find the Use Edge option?

#### nkpham

##### New member
Does anyone know the best way to make a 3D curve from the equations of two 2D curves?

#### nkpham

##### New member
Does anyone know the best way to make a 3D curve from the equations of two 2D curves?

#### kvision

##### Moderator
It seems your question is the problem.

You don't need to know how to make a 3D curve from 2 2D equations.

To make a curve by equation you need to pick a CSYS. Make a sketch plane whereever you want it to be and then create a CSYS so that the X and Y axes are in that plane. Now make your curve by equation using that csys. Do the same for the 2nd curve by equation. Now you can use curve by 2 projections select one of the planes you made the curves in as your sketch plane and use edge to copy the curve. Repeat for the 2nd curve and you will get a 3D curve from tyour 2 2D projections.

A Better way may be to use extruded surfaces using the 2 equations curves and then do a curve at intersection of surfaces. THis is in effect what 2 projections is.

Good luck

#### nkpham

##### New member
Thank you!!! I got it to work. =)