Cut surface below headroom

Hello,

I am working on a project that uses series of two or more helicoids of different characteristics (heights, radii, direction of rotation, etc.). In order to evaluate the usability of the many different options available, I have been working on a grasshopper routine that would cut off the parts of the helicoids which do not allow for enough headroom to walk underneath them.

As you can see from the attached file, the plan is to:

1. Measure the height through vertical lines linking a series of points contained in both surfaces.

2. From the collection of points whose distance to the surface above is less than the necessary headroom, select the most exterior points. These points define the area within the surface which does not have enough headroom.

3. Link these points and project the resulting polyline onto the above surface.

4. Cut the above surface with the projected polyline.

The problem I am having, however, is that I am unable to appropriately close the polyline defined by these points.

Amongst the different options tested, I have tried using the Delaunay Edges tool in order to draw the outer line of the group of points. However, this does not seem to work as this tool does not link closest points (it jumps to the next exterior point). I have also searched in the forum but have not found any discussions which could help me figure this out.

I am stuck so any help is very much appreciated.

Many thanks,

Sergio.