Artlantis 4.5 (and AC) billboards and Piranesi do not mix. This is no doubt obvious to long term Piranesi users.
Artlantis 4.5 billboards are alpha masked images mapped onto a rectangular plane. That entire rectangle comes across in Piranesi as the billboard material, messing up painting. See the attached image of a woman sitting on a sofa - material view and RGB view. Painting in RGB is ugly just to emphasize that the alpha-masked parts of the woman's billboard cannot be painted...because the full billboard rectangle covers up what is behind.
The same thing would happen with the bitmapped trees and people from ArchiCAD I would imagine.
So, tip of the day to new Piranesi users (like me): don't use billboards in Artlantis or AC, or at least delete them before exporting to EPix format. Piranesi cutouts have much more control anyway.
Karl
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB