How to select bottom surfaces

Hello everyone
I’m trying to develop a simple python plugin which draws a sort of “halo” around the bottom surface of a polysurface ( I’ll use that to avoid nesting objects too close to each other )

import Rhino
import scriptcontext
import rhinoscriptsyntax as rs

def Halo():
    OBJ = rs.GetObjects("Select objects to nest:", 16, False, True, True, True)
    if not OBJ: return
    
    for ObjId in OBJ:
        Surfaces = rs.ExtractSurface(ObjId, 0, True)
                
        for SrfId in Surfaces:
            Edges = rs.DuplicateEdgeCurves(SrfId)
            rs.DeleteObject(SrfId)
            JoinedEdges = rs.JoinCurves(Edges)
            rs.DeleteObjects(Edges)
            
            for EdgeId in JoinedEdges:
                col = rs.CreateColor(255,0,0)
                Direction = (1000,1000,1000)
                OffsetEdges = rs.OffsetCurve(EdgeId, Direction, 20)
                rs.DeleteObjects(EdgeId)
                
                for OEId in OffsetEdges:
                    rs.ObjectColor(OEId, col)
                    Grp = rs.AddGroup()
                    rs.AddObjectsToGroup([ObjId, OEId], Grp)
                
if __name__=="__main__":
    DoHalo()

This won’t work because the surface “0” is not always the bottom one, as I could have rotated the objects. Question is :

How can I select the surfaces facing down or, at lest, the surfaces laying on the C plane ?
Or even better, is there a way to select the largest one between the top and bottom surface ?

Of course I am open to any better solution

Thank you !

2 posts - 2 participants

Read full topic