By "opaque", do you mean the glass should let some light go through, but without being able to distinguish objects being the glass?
Yes, exactly !Not sure it's really possible in Sweet Home 3D, but you can try with some glass...
I did many tries without success. 
An idea : I read this morning a fetaure of enko on light about a vertical surface...
but how make this object ?
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Evil progresses when good people do nothing!
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SH3D 7.1 and nothing else - W11 64b in 4K
