Curves get their 3D position:
• from the curve projection algorithm when the curve is referenced on two or more oriented photos
- fires when a curve has marks referenced/unreferenced
- fires when a curve point is added/removed/moved in a curve mark
- fires when one of the photos its mark appears on is oriented, reoriented or forced unoriented
- fires when the user changes camera parameters or camera station parameters for that photo
- fires after global optimization
Note that there are special requirements for photography to properly create curves. See the Quick Start Guide section Photography for Curves, Edges and Cylinders.