Bug: Subobject Material Assignment


I wanted to note an odd bug when using Sub-Object material assignment. On some Breps, when you select a single subobject (command-shift-click) and ‘Assign to Objects’ the material gets assigned to multiple faces, instead of just the single face selected. Obviously this is not ideal.

Single closed polysurface with multiple sub-surfaces

Create a single new material and try and assign to a SINGLE surface:

Material gets assigned to two surfaces??

(Note also, the unwanted ‘Custom’ material is created and added to the scene: see link for more information on that)

I have attached the example file here for reference.


  • Macbook 2021, Apple M1 Max
  • OS 12.5.1 (Monterey)
  • Rhino Version 7 (7.21.22208.13002, 2022-07-27)))

thank you very much,

material_assignment_example.3dm (3.4 MB)

Hi Ed -

Thanks for that example - on the list as RH-70021 Rendering: Materials: Sub-object assignment adds multiple surfaces