Lester Banks, one of my favorite blogs, linked this tutorial from Mike, but he took it further. Mike addresses a bit about UDIM, the UV offset that Mari utilizes and how to deal with a slowdown that occurs when separating the UV’s in Modo. It will help to be super efficient
What in the heck does that mean? I did not know, but Lester links to an article by Ben Neall called Mari UDIM Color Space Guide for Texture Artists, which explains UV Space, separating UVs Tile and finally the UDIM. Hopefully this will make it all crystal clear.
Need more info, like UV Map tutorials, tools and grids? Check out the Polycount Wiki.