Seperation plane following closed curve

I often work with complicated osteotomy geometry that doesn’t follow straight lines or curves.
I need to experiment with many shapes to see the outcome. it would be so good if I could draw a closed curve and a plane is fitted through it

This feature is already available. Your can get the curve coordinate system (plane position, tangent, normal direction) at any curve point. There is also a nice module with a convenient GUI in SlicerVMTK extension: Cross-section analysis module.

Placing curve is not the issue . The request is about having a fitted plane or planes in the closed curve area to perform the cut .

I thought you need to fit the plane orthogonally to the curve. Fitting a plane in the curve points is even simpler. Have your tried using plane fit mode? It draws the plane by fitting it on all the control points that you specify.

A post was split to a new topic: Failed to load nifti file

never noticed before, and could not figure out how to use it .
not clear how to select points and initiate fitting