Sorry everyone but english is not my mother language and I don't understand something :blushing:

you say "a smoothing id, a numeral" this means the two groups just need to have a different id no matter what the numeral is?

I selected all in a group gave a smoothing id of "1"

than selected the keystone polygons you show and gave a smoothing id of "2" (second image)

the object acts around the keystone like before plus the pillar now acts different that having smooth on for all the object

 

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