Fillets are easy in Rhino

The 3d model seen in the thumbnail image has two different display modes assigned to its surfaces. The graphite one is called "Crackdown 1", while the yellow one is "Зайо Байо" (written in Bulgarian alphabet in my Rhino 7). Both custom display modes could be downloaded from the following topic on the official Rhino forum:
https://discourse.mcneel.com/t/share-your-custom-viewport-modes-here/151321