Mirror UVs for normal maps

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Does Unity supports mirrored UVs for normal maps? It is my understanding that the artist wants to have a full model, but with the final unwrap include only 1/2 a symmetrical normal map, then use mirrored UVs to map it to both halves of the model, but we're unclear on if this is supported by Unity.

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Answer by equalsequals · Nov 27, 2009 at 10:43 PM

If I am understanding you correctly, you are asking if you can take a mesh, (i.e. half of a person) and UV map it, then use a mirror modifier to make it into a symmetrical mesh?

If so, yes Unity supports this.

The process goes as follows:

Create the half mesh in your editing software
Unwrap the UV on the half-mesh
Texture it
In the editing software apply the mirror modifier
save and drag n' drop into unity or export as FBX - whichever.

You should be good-to-go.

Cheers!

==

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Ricardo · Nov 27, 2009 at 10:59 PM 0

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Thanks for the answer. Actually the intention is to have a full model, UV mapped, but with just half the normal texture that is then mirrored into the full mesh. I've clarified the question.

equalsequals · Nov 28, 2009 at 03:39 AM 1

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No problem. The answer is the same. :)

Ricardo · Nov 28, 2009 at 05:01 AM 0

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Great, excellent. I'll let them know, we'll see if the same goes if the model is already created, but has yet to be textured.

Answer 2

Answer by user-9122 (google) · Feb 10, 2011 at 10:11 AM

I know this is an old question, but I'm updating it so if other people are searching for this they'll get some better information.

Technically your normal map will work, it'll just appear to be inverted (creases in will appear to go out, ect.) on the mirrored half. If you're just painting your normal maps in photoshop it probably won't look as bad as if you where baking them from a high poly source.

It's up to the artist to decide whether to do this or not. If it's just on some environment pieces or stuff that won't be close to the camera, go for it. If it's on a character spend the extra time to do it right.

When I'm doing anything with normal maps I make sure my UVs aren't flipped/mirrored. If you have overlapping UVs that's fine, as long as they're not mirrored and not overlapping if you're baking out your normals.

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Daniel-Brauer · Jun 07, 2011 at 02:04 PM 1

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This is incorrect. All of Unity's built-in shaders and all surface shaders support mirrored tangent space using homogeneous tangent vectors. This means that if your modelling program outputs tangents with the correct W component (1 for normal, -1 for mirrored), then normal maps will look fine even if the UVs are mirrored. Here is an explanation: http://forum.unity3d.com/threads/65859-Symmetric-models-with-mirrored-normal-maps-Shader-Fix?p=420888&viewfull=1#post420888

The one place where your modelling program probably won't help you is on the UV seams that transition from normal to mirrored. For these places, you have to make sure that your normal map is continuous when mirrored. Here is a good explanation of how to do this: http://www.polycount.com/forum/showthread.php?t=51088

Answer 3

Answer by IgorAherne · Mar 21 at 07:52 AM

Make sure than in the import settings of your objects you select the tangents as "Import"

alt text

ctrli-jpg.jpg (308.4 kB)

tangents.jpg (158.0 kB)

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Mirror UVs for normal maps

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