UDIM and texture exports problems (PLEASE ASSIST)

[Traile]

Hi, I'm really in need of some assistance to export a mesh with UDIM textures from speedtree and I'm not having the expected results. The problem is that the UV on the leaves and fronds is stretched out and the texture maps are not square but rectangular. My guess is that when these textures are loaded in as texture maps in a DCC, they will get stretched to match the stretched UVs because the albedo maps appear to render correctly. But some renderers seem to not like this. Also, it causes a problem if I want to take the model into substance painter for further work. How can I get square textures and non-stretched UVs?

[Greg Croft]

Hello,

There is no requirement that UDIM textures be square that I am aware of, though it is the norm. No matter what size or aspect ratio the texture is, your UVs would not change in this case. You could, in fact, resize the texture to be square and it should work the same (though the texture may become lower in quality from that edit).

Are you asking why you have two leaves in a map with a lot of space in between? That might be because you have cut them out of an atlas, but the mesh handling for that material is set to share. On the material asset for that leaf, switch to the cutout tab. In there is an option you can switch between share and separate. On separate, you should get each leaf in it's own uv area (ie it's own UDIM texture).


> it causes a problem if I want to take the model into substance painter for further work

For anything you wish to paint, in the unwrap UVs dialog you need to make sure they are set to "Unwrapped" (where each item gets its own uv area / UDIM tile) instead of "Stacked" (where all the leaves needing a particular texture will reference the same uv area). It looks like you have them set to stack. By default branches are set to unwrapped but leaves are set to stack, because you usually don't need to paint those.


Hope this helps

[Traile]

Hello,

There is no requirement that UDIM textures be square that I am aware of, though it is the norm. No matter what size or aspect ratio the texture is, your UVs would not change in this case. You could, in fact, resize the texture to be square and it should work the same (though the texture may become lower in quality from that edit).

Are you asking why you have two leaves in a map with a lot of space in between? That might be because you have cut them out of an atlas, but the mesh handling for that material is set to share. On the material asset for that leaf, switch to the cutout tab. In there is an option you can switch between share and separate. On separate, you should get each leaf in it's own uv area (ie it's own UDIM texture).


> it causes a problem if I want to take the model into substance painter for further work

For anything you wish to paint, in the unwrap UVs dialog you need to make sure they are set to "Unwrapped" (where each item gets its own uv area / UDIM tile) instead of "Stacked" (where all the leaves needing a particular texture will reference the same uv area). It looks like you have them set to stack. By default branches are set to unwrapped but leaves are set to stack, because you usually don't need to paint those.


Hope this helps

Thanks for the response, the stretched out UVs is what I was hoping could be resolved(any other texture applied to leaves would be distorted due to the UV stretching). Notice how the UV leaves are stretched compared to the width of the texture. It does, however render correctly with the leaf texture exported from speedtree but if there is a way to get total visual parity between the texture and UV I would prefer that.