|<udim>||texture_<udim>.tx||texture_1001.tx, texture_1002.tx, texture_1003.tx, etc.|
|<tile>||texture_<tile>.tx||texture_v1_u1.tx, texture_v1_u2.tx, texture_v1_u3.tx, etc.|
A cylinder with its side in u0,v0, base in u0,v1, and top in u0,v2
UDIM values are a way of representing the integer coordinates of a texture, from the coordinates of its bottom-left corner in UV space. This way, multiple textures can be used to cover a model, rather than a single, much larger, texture.
Faces of a cube unwrapped in u0,v0, to u0,v5,
It is a 4 digit number starting at 1001, created using the formula, 1001 + u + (10 * v)
In the example above the side would be 1001, base 1002, and top 1003.
To use this method in your file inputs, use the <udim> tag in the file name, which is then replaced with the appropriate number.
texture.<udim>.exr will be read as
texture.1001.exr when looked up for rendering.
texture_<udim>.tx will be read as texture_1001.tx when looked up for rendering.
Check out Ben Neall's page for a clear description of UDIM numbering.
When the path to the image used in sib_image_clip contains such a token, the actual name of the image to be used is resolved, depending on the current UV coordinates.
Here is one Mari case in action.
Note that, unfortunately, the path turns red when you edit it to replace part of its name with the <udim> token, but there is nothing we can do at the moment.
When using the <tile> token, multiple textures can be used to cover a model, rather than a single, much larger, texture. It is the notation at which it is exported in UV texture space. This starts at 1001 (0,0) and continues in U for another 10 offsets. It then progresses onto the next row of V, meaning for every 10 in U it moves 1 in V.
UV's should be arranged into separate UV tiles in order to maximize texture space
You can use a single File texture to open textures composed of multiple images that correspond to the grid tiles in your UV layout. You can, therefore, open and render high-resolution textures produced by 3D painting applications such as Mudbox, and is a better alternative to using UVsets.