Remove normals from single mesh face

Scripting
1

Hi,
my progress stopped understanding the rhino behavoir as i’m unable to remove normals from a mesh i have exploded into single faces.

In the example file the explode is done on the left with a commercial plugin that creates mesh faces without normals. If i make a mesh offset i get perfect quad elements.

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My own script always creates a normal on the face the leads to intersecting quad elements.
is there a way to remove this normal?

import rhinoscriptsyntax as rs
import Rhino.Geometry as rg
import scriptcontext as sc
import Rhino
import scriptcontext
import math
import os


def unweld_all_faces(mesh_id):
    # Netz aus der Rhino-Dokumentation abrufen
    mesh = rs.coercemesh(mesh_id)
    
    if not mesh:
        print("Kein Netz gefunden.")
        return
    
    # Das Netz explodieren (d.h. in einzelne Faces zerlegen)
    exploded_meshes = []
    
    for face_index in range(mesh.Faces.Count):
        # Extrahiere jede Face als einzelnes Netz
        single_face_mesh = Rhino.Geometry.Mesh()
        
        # Hole die Eckpunkte der aktuellen Face
        face = mesh.Faces[face_index]
        vertices = [mesh.Vertices[face.A], mesh.Vertices[face.B], mesh.Vertices[face.C], mesh.Vertices[face.D]]
        
        # Füge die Vertices zum neuen Netz hinzu
        for vertex in vertices:
            single_face_mesh.Vertices.Add(vertex)
        
        # Füge die Face zum neuen Netz hinzu (unabhängig von der Anzahl der Punkte)
        if face.IsQuad:
            single_face_mesh.Faces.AddFace(0, 1, 2, 3)  # Quad Face
        else:
            single_face_mesh.Faces.AddFace(0, 1, 2)  # Triangular Face
        
       #Normals, Texturen, Farben usw. können hier auch übertragen werden, falls nötig
       #single_face_mesh.Normals.ComputeNormals()
       #single_face_mesh.Compact()
        
        # Füge das explodierte Netz zur Liste hinzu
        exploded_meshes.append(single_face_mesh)
    
    # Lösche das ursprüngliche Netz
    rs.DeleteObject(mesh_id)
    
    # Füge die explodierten Netze zur Rhino-Dokumentation hinzu
    for single_mesh in exploded_meshes:
        sc.doc.Objects.AddMesh(single_mesh)
    
    sc.doc.Views.Redraw()
    print(f"{len(exploded_meshes)} Faces erfolgreich unwelded und explodiert.")

mesh = rs.GetObject("getmesh")

unweld_all_faces(mesh)
2

Hi @David_Seidel,

It’s unclear me what you are trying to do. Perhaps you can explain?

If you create a mesh without vertex or face normals and then add that mesh to the document, Rhino will compute and add the normals to that mesh.

– Dale

3

Hi Dale
I want to make an Offsetmesh to all single faces and create finite Elements.

The thrid Party Plugin creates Mesh faces without normales. I Wonder how this is achieved.

If there ist a normal offsetmesh will not work as intended.

4

Still trying…

I tried to extract every single mesh face with “_extractmeshfaces” but it seems not possible to select the faces with a for loop.

I works if i extract by hand. but i dont get it running to select facex from meshy

5

It looks to me like what you need is not so much to remove normals, but rather to have matching normals at the shared vertices.
Instead of exploding the mesh at the start, you can iterate through the faces, get their 4 vertex indices and then use the vertex normals at these indices when creating your offset.

6

Sounds like a plan.

7

Thank you. This was the solution. Hero :partying_face:


import rhinoscriptsyntax as rs
import scriptcontext as sc
import Rhino

def unweld_all_faces(mesh_id):
    # Netz aus der Rhino-Dokumentation abrufen
    mesh = rs.coercemesh(mesh_id)
    
    if not mesh:
        print("Kein Netz gefunden.")
        return
    
    # Das Netz explodieren (d.h. in einzelne Faces zerlegen)
    exploded_meshes = []
    
    for face_index in range(mesh.Faces.Count):
        # Extrahiere jede Face als einzelnes Netz
        single_face_mesh = Rhino.Geometry.Mesh()
        
        # Hole die Eckpunkte der aktuellen Face
        face = mesh.Faces[face_index]
        vertices = [mesh.Vertices[face.A], mesh.Vertices[face.B], mesh.Vertices[face.C]]
        
        # Füge die Vertices zum neuen Netz hinzu und kopiere die Normalen
        for i, vertex in enumerate(vertices):
            single_face_mesh.Vertices.Add(vertex)
            # Kopiere die Normalen der Vertices
            normal = mesh.Normals[face[i]]  # Hole die Normalen des entsprechenden Vertex
            single_face_mesh.Normals.Add(normal)
        
        # Füge die Face zum neuen Netz hinzu
        if face.IsQuad:
            single_face_mesh.Vertices.Add(mesh.Vertices[face.D])  # Füge den vierten Vertex bei Quad hinzu
            single_face_mesh.Normals.Add(mesh.Normals[face.D])  # Füge den vierten Vertex Normal hinzu
            single_face_mesh.Faces.AddFace(0, 1, 2, 3)  # Quad Face
        else:
            single_face_mesh.Faces.AddFace(0, 1, 2)  # Triangular Face
        
        # Komprimiere das Netz
        single_face_mesh.Compact()
        
        # Füge das explodierte Netz zur Liste hinzu
        exploded_meshes.append(single_face_mesh)
    
    # Lösche das ursprüngliche Netz
    rs.DeleteObject(mesh_id)
    
    # Füge die explodierten Netze zur Rhino-Dokumentation hinzu
    for single_mesh in exploded_meshes:
        sc.doc.Objects.AddMesh(single_mesh)
    
    sc.doc.Views.Redraw()
    print(f"{len(exploded_meshes)} Faces erfolgreich unwelded und explodiert.")

def main():
    # Benutzer wählt ein Netz aus
    mesh_id = rs.GetObject("Bitte das Netz auswählen", rs.filter.mesh)
    
    if mesh_id:
        unweld_all_faces(mesh_id)
    else:
        print("Kein Netz ausgewählt.")

# Skript ausführen
main()
1 Like