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Normal seams in unreal.

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JoW node
Hey there, long time no posting here, hope this community is still active and hasn´t moved to facebook or discord...

So, I have bit of a complicated problem, so bare with me.

I´m working on a shortfilm. Its a collaborative project, character animation is done in maya and shading/lighting/rendering in 3ds max.
But now I wanna move to unreal.
I started testing with my main character and although its looking good, I can´t get rid of the UV seams.
It was originally cut in 11 UDIM tiles, but for unreal (as I couldn´t find good info on the use of udims) I wanted to bake it down to on 8k tile, so I simple repacked the UVs to one tile in max.
I´m sure I could do a better job hiding the seams, if thats necessary.

The maps were created in mudbox, but I can´t get it to reimport the new UVs. 
So admittedly very crude workflow was to bake the normals in the diffuse slot of a standard material from channel 1 (old 11 UDIMS)  to channel 2 (new packed to one tile).

This seemed to work for all other textures, but not for normals, as I get shading seams in unreal.

In the end there will probably be even more issues, as my maya rigger already left and I don´t know how to change the UVs in maya, so I´ll probably be left with exporting from maya via alembic, importing the alembic to max, copy pasting the new uvs to the alembic and then exporting the alembic for unreal...

But for now all I wanna know is,
1. Is it even possibly to get seamless normals with my mesh with the current UV set? If its a general problem with normal maps in unreal and I just need to unwrap it better, I can save myself the time to troubleshoot possibly other causes.
2. Does anybody have experience with mudbox when it comes to importing UVs? Ideally I´d stay inside of mudbox without moving between mudbox/3dsmax and possibly xnormal for all future textures changes of the character...

I´ve attached the UVs as well as the test in unreal.


  • CheeseOnToast
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    CheeseOnToast greentooth
    If you rotated the UV shells in any way, the normal map will no longer be correct and will need to be rebaked. Also, downsampling like this may introduce artifacts at seams as  well. It should be perfectly possible to bake a seamless normal map.

    Tangent space is another thing to consider. Unreal uses MikkT space. If your baker (Mudbox in this case) uses some other tangent space, it will introduce errors.

    If this is a "one and done" kind of thing, I can have a go at baking the normal map for you. I'd need access to the high and low poly models in OBJ format if possible.
  • JoW
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    JoW node
    Ok, thanks. Thats all the answer I needed for now.
    Thanks for the offer, but its definitely not gonna be a one off. For testing purposes, yes, but I´ll have to export other textures from mudbox, possibly change normals etc and so I´ll have to figure out how to get it to accept the new UVs, so I don´t have to use dumb workarounds that don´t work...:)

  • papa335677
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    Did you ever find a fix or at least figure out what causes this?

  • sprunghunt
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    sprunghunt polycounter

    There are multiple issues that can cause this. Most of them are fairly standard between different engines.

    One thing I can see is that the normal map doesn't have a blue background or any dilation on the edges. You need to have this to hide seams caused by mipmapping.

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