3D Splines

Hello

Please could someone explain how to constrain a 3D spline.

I've drawn one in a model I am trying to construct. It forms one side of a 3D sketch which will be the end of a loft feature, and is formed from 3 points in space.

Thanks.

I would like to know the same thing. I typically make construction lines(planes in this case) at certain points and use the tangent constraint. I dont know if there is a proper method but id like to see what the replies are. When possible i create a 2d spline and project it onto a surface to get my 3d curve.