About UDIM: You can add an offset to the existing UV-coordinates to move certain areas to a UDIM-Page you like.

AS you know, UV-coordinates are values between 0.0 and 0.999~ in U and V direction.

UDIM is defined as a table of rows (0 to 9) and columns (0 to 9). To be able to address an UDIM-Row/Column the row address is added to V (0 to 9) and the column address is added to U (0..9). In the rare case you need more then a 10 x 10 matrix, you may define UDIM "pages" (page, rest = divmod(coord, 10x10); row, col = divmod(rest, 10); col, coord =divmod(col, 1.0))

If an UV coordinates is set to 2.123/0.678, then this means: UDIM row 2 (V) and UDIM column 0 (U). Each and every software uses the coordinates U = 2.123 modulo 1.0, V = 0.678 modulo 1.0 to address this UV coordinate (yes, the stacked version :) )

UV = 3.456/4.215734 == UDIM row 3, column 4, coordinates 0.456/0.215734

FYI: Poser 12 allows to manipulate UV coordinates from a loaded mesh. This was broken in P11 and not available in earlier versions. Now it works and allows some fun – what about UV-morphs?

Some time ago I made a Python script on request to demonstrate UDIMs: https://adp.spdns.org/#UDIM

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