How to open / close a control point spline

[twan_peeters]

How can I open or close a control point spline properly? With the fit point spline you can right click and hit 'close', but this option is not there for the control point spline.

Whenever I just connect the two ends of the spline manually, it only creates a coincident constraint, it doesn't actually properly connect the two points in a smooth way as you can see in curvature of the spline below.

Even though I can line it up manually by myself to make it look as smooth as possible, it is giving me problems further down the line in the modelling stage, such as not allowing me to apply fillets.

[jeff_strater · Accepted solution]

I think to create a tangency condition for a control point spline, you need to make the lines of the adjacent control polygon colinear.  If you go two spans back, that is a "smooth" or G2 condition.

[TrippyLighting]

Here's a link to the relevant section of the Autodesk Alias Theory Builders 

[twan_peeters]

This did it for me, thank you. Although I do find it strange that this is necessary and it can’t just close it out of itself! It also limits how you can design the spline, but for this instance it works.