Wish - SHRINKWRAP COGO Points in Point Group

It so sad to hear… RIP, Terry!

An alternative is to use scipy.spatial, which may have other goodies

import traceback
from pyrx import Ap, Ax, Db, Ed, Ge, Gi, Rx

# maybe has other usful tools
from scipy.spatial import ConvexHull

@Ap.Command()
def doit() -> None: # change me
    try:
        db = Db.curDb()
        
        ps, ss = Ed.Editor.select([(0, "POINT")])
        if ps != Ed.PromptStatus.eOk:
            raise RuntimeError("Selection Error! {}: ".format(ps)) 

        # get all the positions 
        pnts = [Db.Point(id).position() for id in ss.objectIdArray()]
        
        # compute the hull with a Z of zero
        hull = ConvexHull([pnt.to2d().toTuple() for pnt in pnts])
        
        # extract the hull points using indexs
        segs = []
        for simplex in hull.simplices:
            segs.append(Ge.LineSeg3d(pnts[simplex[0]],pnts[simplex[1]]))
            
        # create a composit curve 
        results = Ge.CompositeCurve3d.createFromLineSeg3dArray(segs)
        for item in results:
            # BricsCAD will create a 3d polyline if the points arn't planar
            dbo = Db.Core.convertGelibCurveToAcDbCurve(item)
            db.addToCurrentspace(dbo)

    except Exception as err:
        traceback.print_exception(err)

Having spent way to many years playing with TIN's there is an error in the convex hull shape if you look closely at the image the boundary skips across a large indent, lower left, a true boundary would actually follow this shape.

One other way is to use the TINS to make an outer shape but its not quick as you need to get rid of long triangles. Make a 3dfaces and so on.

The main reason for wanting boundary is when comparing to another surface eg Volumes.

Supplementary to the above, i would like to point out that the functionality of creating a concave hull 2D is available via the TIN, TINEDIT and TINEXTRACT command…

1. create a TIN using a set of points, a group of points or a point cloud

:TIN
Select entities to create TIN surface or [Import from file/place Points/create from Faces/create from point Cloud/create from point Groups/create from cOntours/create from Mesh/cLip polygon/selection options (?)]:
Opposite Corner:
Entities in set: 4202

2. Remove the outer edges thus creating the outer concave hull boundary of the tin surface using the TINEDIT command

: TINEDIT
Select TIN surface [selection options (?)]:
[Add Points/Add Point Groups/Add Breaklines/Add bOundaries/Remove Points/Swap Edge/Point Location/Point Elevation/Add Line/Delete Line/Remove Outer Edges/Minimize Flat Areas/Remove Elevations/SMoothing]: ROE
Define concavity and lengthThreshold in the pop-up window

3. Extract a concave hull 2D (3d polyline) of the tin surface boundary using the TINEXTRACT command

: TINEXTRACT
Select Surface [selection options (?)]:
Entities in set: 1
Select Surface [selection options (?)]:

Extracting ...

Extracting borders: 1 entities extracted.
Total entities extracted: 1.