Temporarily draw naked edges on breps, meshes, extrusions and SubD objects.

DrawNakeds.py

import rhinoscriptsyntax as rs
import Rhino
import scriptcontext as sc
import System

class DrawEdgesConduit(Rhino.Display.DisplayConduit):
    def __init__(self, crvs):
        self.crvs = crvs
        self.pts = [crv.PointAtStart for crv in self.crvs]
        self.pts += [crv.PointAtEnd for crv in self.crvs]
        self.pts = list(set(self.pts))
        self.color = Rhino.ApplicationSettings.EdgeAnalysisSettings.ShowEdgeColor
        self.bbox = Rhino.Geometry.BoundingBox()
        for crv in crvs:
            self.bbox.Union(crv.GetBoundingBox(True))
    def CalculateBoundingBox(self, e):
        e.IncludeBoundingBox(self.bbox)
        
    def DrawOverlay(self, e):
        for item in self.crvs:
            e.Display.DrawCurve(item , self.color, 4)
        for item in self.pts:
            e.Display.DrawPoint(item, self.color)

def DrawNakeds():
    id = rs.GetObject('Select an object for edge display', filter = 8 + 16 + 32, preselect=True)
    if not id: return

    geo = rs.coercegeometry(id)
    
    if isinstance(geo, Rhino.Geometry.Extrusion):
        geo = geo.ToBrep()
    es = []
    if isinstance(geo, Rhino.Geometry.Brep):
        for edge in geo.Edges:
            if edge.Valence== Rhino.Geometry.EdgeAdjacency.Naked:
                es.append(edge.ToNurbsCurve())

    elif isinstance(geo, Rhino.Geometry.Mesh):
        eList = geo.TopologyEdges
        for n in range (eList.Count):
            if len(list(eList.GetConnectedFaces(n))) == 1:
                es.append(eList.EdgeLine(n).ToNurbsCurve())
    elif isinstance(geo, Rhino.Geometry.SubD):
        eList = geo.Edges
        for edge in eList:
            if (edge.FaceCount) == 1:
                es.append(edge.ToNurbsCurve(True))

    if len(es) == 0:
        print('No nakeds found.')
        return
            
            
    conduit = DrawEdgesConduit(es)
    conduit.Enabled = True
    sc.doc.Views.Redraw()
    
    go = Rhino.Input.Custom.GetOption()
    go.SetCommandPrompt(str(len(es)) + ' naked edges found. Press <Enter> to continue')
    go.AddOption('DuplicateAndExit')
    go.AcceptNothing(True)
    
    rc = go.Get()
    
    if go.CommandResult()!=Rhino.Commands.Result.Success:
        return
    if rc==Rhino.Input.GetResult.Option:
        out = []
        for item in es:
            out.append(sc.doc.Objects.AddCurve(item))
        newGroup = rs.AddGroup()
        rs.AddObjectsToGroup(out, newGroup)
        rs.SelectObjects(out)
        
    conduit.Enabled = False
    sc.doc.Views.Redraw()
        
if __name__ == '__main__': DrawNakeds()