One method for creating 3D curves is by joining a number of 3D Object Points using the “Curve from Points” mode.
To create a Curve from Points:
• Open a photograph or 3D view window that shows all the Object Points you want the curve to pass through.
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Go into Curve from Points mode 
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• Select the points in order that the curve should pass through. At least two points must be selected for the curve to be created. It is a good idea to have a 3D Viewer open or projections turned on so you can see the curve being created.
If a Curve from Points is draw between two points it is a linear curve (degree 1) (i.e. a line), if between three points it is a quadratic curve (degree 2) and for four or more points it is a cubic curve (degree 3).
Curves created with this method are pure 3D objects (much like Surfaces) and in this fashion do not appear on photographs. They appear in the 3D Viewer and in photo projections when they are properly defined. They are also listed in the Curve Table. In a Curve Table they are shown with no photographs.
If any of the points in this type of Curve lose their 3D position the Curve will reinterpolate though the remaining 3D points. When the point positions update the Curve will be reinterpolated to pass through them.