Written on one afternoon out of frustration with having to constantly adjust snap grid positions and angles for my reflected ceiling plans. We still do them the good ol' way -- using slabs and cover fills, so precise and efficient placement of fixtures has always been a bit of a headache.
I don't know what solution you use, but this here is turned out to be pure joy (well, compared to what I did before).
This is not some super-smart object with advanced logic, but it serves its purpose, and I haven't found anything similar in my ArchiCAD. Please experiment with the "alignment" vs "snap" grid size and you'll get the concept.
The basic idea is to just place the built-in diagonal line in two corners of the room and immediately receive an automatically aligned snap grid for your acoustical ceiling tile. Extra rows of snap points can be added around the perimeter. See illustration in post below (I haven't figured out how to add multiple attachments)
NOTE: this object uses imperial units, but that's an easy change in the parameters. Public license 😉
