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Question: metahuman UVs align to the edges. The textures strech. Is this unwrapping good? why?

Checking out Epic's metahuman UVs, I noticed that the UVs are squared all the way to the edges of the DIM.

I have seen other professional heads doing the same thing; professionally scanned textures are squared too.

As you can see in the pictures below, the UVs follow a checkered pattern very well from the front, but behind the ears; the back of the head; and the bottom of the neck, all present quite some distortion.

Is this distortion acceptable? If so, to gain what? Cover a larger area of the UDIM? I have seen work that aligns the face's UVs to the edges and also others that don't, like Epic's Paragon characters.

What are the pros and cons of these choices? What is the industry standard? How do you UV unwrap faces?


Replies

  • Fabi_G
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    Fabi_G quad damage

    Hi! UV borders aligned to pixel grid reduce texture seams showing (Aliasing on UV seams), which is my guess why it's prioritised over stretched UVs.

    Stretched UVs are moved out of prominent areas of the model (face) to places that are less in focus or covered up.

    Textures baked from a highpoly and non UV projected patterns used during texturing will not look stretched on the model.

    Tiling microdetail textures added in shader will show some stretching, but I doubt it's very noticeable at that scale and their intensity is likely controlled by a mask.

  • dMartinezMoreno

    This is a great answer, thank you!

    I guess that if the baked texture or scanned texture is also stretched in the same way, it ends up looking right.

    The cons: in addition to tiling, wouldn't any in game real time decals, like blood splatters, also stretch? Is it safe to say that border aligned UVs are better for ofline rendering?

  • Fabi_G
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    Fabi_G quad damage

    Hi! I'd say aligning UV borders to pixel grid whenever it makes sense is a good practice for games, as it will minimize seams showing with lower texture resolution (mipmapping). With offline rendering, where one can use more, higher resolution textures it becomes less relevant imo.

    I believe stretching with decals depends more on the way they are projected. As with all things there are multiple ways to implement this, specific solution for the project has to be found. A system that is independent of the base character might be desirable. One could inspect this addon.

  • Kanni3d
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    Kanni3d ngon master

    Decals are typically projected in 3d space, not UV space, so no - they shouldn't stretch. (although if you were to place a decal in the uvs directly, then yes they would stretch).

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