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So, something I've never quite been able to understand are UDIMs. I mean, I get it, you use multiple tiles and thus multiple textures instead of having one giant one which may save up on resources.

I have a character that has a lot of exposed skin and I want it to all have equal detail, so i created three tiles.

1- Body and clothing 2- Legs, feet, arms and hands 3- Head

I decided to give 4k to the first one and 2k to the other two, however, this method creates horrible seams. So what am I doing wrong? Do all the tiles need to be the same resolution? Is this really a better way compared to just using a 10k or 12k texture?

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The tiles don't need to be all same resolution. But the so-called Texel Density needs to be the same across all tiles if you want to avoid seams. Texel density is the area occupied by a UV island relative to the resolution of the image.

Also, UV islands should not cross the tile borders.

Here's an example of a UDIM texture with three different tile sizes:

  • 1024 x 1024px = 1k texture
  • 512 x 512px = 1/4th of the 1k texture
  • 256 x 256px = 1/4th of the 512 texture and = 1/16th of the 1k texture

If you UV unwrap it, Blender will make all UV islands the same size which results in a different texel density and seams. Crossing the tile borders also creates seams:

bad texel density

If you scale the UV islands according to the image size, they will all have the same density.

The left UV is not scaled at all, the middle is scaled up 2 times, and the right one is scaled up 4 times.

Or in other words: Make the island(s) on the image with the lowerest resolution fit the image and scale down the island(s) on the other tiles accordingly. From right to left is: not scaled, 0.5, 0.25.

Now the cube has no visible seams and all squares have the same size:

equal texel density

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  • $\begingroup$ Thank you. This is exactly the type of information that I was looking for. For some reason, videos talking about UDIMS never even mention this. So, thank you! $\endgroup$
    – Filnisius
    Nov 10, 2021 at 14:21

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