RhinoCommon UnrollSurface differs from UnrollSrf command

Scripting
,
14

Hi again @dale, running into another discrepancy between the UnrollSrf command and rhinocommon implementation. Could you share some insights in the joining process after unrolling as used by the UnrollSrf command?
When I use the JoinBrep method from RhinoCommon with the tolerance used in the RhinoScriptSyntax implementation, as I got explained by Willem in this topic, it doesn’t join 1 part of the unrolled surface whereas UnrollSrf returns one single polysurface. I tried on this file using the code below:

220226 UnrollSrfJoin.3dm (240.4 KB)

import Rhino
import scriptcontext as sc

def test_unroller():
    filter = Rhino.DocObjects.ObjectType.Surface | Rhino.DocObjects.ObjectType.PolysrfFilter
    rc, objref = Rhino.Input.RhinoGet.GetOneObject("Select surface or polysurface to unroll", False, filter)
    if not objref or rc != Rhino.Commands.Result.Success: 
        return
    
    brep = objref.Brep()
    if not brep:
        return
        
    bcopy = brep.DuplicateBrep()
    bcopy.Compact()
    bcopy.Faces.SplitFacesAtTangents()
    for f in bcopy.Faces:
        f.RebuildEdges(0.00001, True, True)
    for f in bcopy.Faces:
        f.ShrinkFace(Rhino.Geometry.BrepFace.ShrinkDisableSide.ShrinkAllSides)
    bcopy.CullUnusedSurfaces()
    for f in bcopy.Faces:
        if f.OrientationIsReversed:
            f.UnderlyingSurface().Reverse(1)
        
    unroll = Rhino.Geometry.Unroller(bcopy)
    unroll.AbsoluteTolerance = sc.doc.ModelAbsoluteTolerance
    unroll.RelativeTolerance = 0.01
    out_breps, curves, points, dots = unroll.PerformUnroll()
    
    if out_breps:
        joinBrep = Rhino.Geometry.Brep.JoinBreps(out_breps,sc.doc.ModelAbsoluteTolerance*2.1)
    
    if joinBrep:
        for b in joinBrep:
            sc.doc.Objects.AddBrep(b)
    sc.doc.Views.Redraw()

if __name__=="__main__":
    test_unroller()