Rotating objects with Tangent-Space Normal Maps.

wetojo

I'm currently trying to model a wagon in 3ds max as a game asset and put it into UE4. I'm relatively new to 3d so this project is a big learning experience for me. I'm having a problem with the spokes of the wheels. I UVed a low poly version of one spoke and baked out detail from a high poly spoke. The plan was to duplicate and rotate the spoke to make the others. As I understand it, there shouldn't be a problem with rotating objects when they are using tangent-space normal maps as opposed to object or world space ones. Regardless of this I'm getting some incorrect lighting both in 3ds Max mental ray and in UE4. I've tried duplicating and rotating the geometry both at the object level and the subobject level. I've received the same effect with both. 

What am I missing here?

I've found a work around, where I can import the spoke as an individual object and rotate it in UE4 with no lighting issues. This does solve my issue but doesn't teach me what I'm doing wrong. Any help would be appreciated.

petemc

Are you using Normal Bump to display your normal map in Max? You may also need to flip the green channel. DO you have a screenshot of your rotated spokes without the normal map applied? The normals on the spoke part look very heavy for the geometry you have, i would also take a look at generating them again, maybe try to keep more of a cylindrical unwrap to that area

ActionDawg

petemc said:

Are you using Normal Bump to display your normal map in Max? You may also need to flip the green channel. DO you have a screenshot of your rotated spokes without the normal map applied? The normals on the spoke part look very heavy for the geometry you have, i would also take a look at generating them again, maybe try to keep more of a cylindrical unwrap to that area

He's rendering in Unreal and the unwrap and geometry aren't problems. If you look at "imported into ue4 and rotated" it's pretty simple geo.

Could you share your files? Preferably the high + low in case there are problems with the bake. Initially I'm not sure what the problem is! It may have something to do with normals getting messed up on export.

cptSwing

Maybe unstacking the uv shells (moving outside of 0,1) might help?

Bruno Afonseca

Are you exporting tangents or generating them in engine? Try both options

https://docs.unrealengine.com/latest/INT/Engine/Content/FBX/ImportOptions/index.html

wetojo

somedoggy said:

petemc said:

Are you using Normal Bump to display your normal map in Max? You may also need to flip the green channel. DO you have a screenshot of your rotated spokes without the normal map applied? The normals on the spoke part look very heavy for the geometry you have, i would also take a look at generating them again, maybe try to keep more of a cylindrical unwrap to that area

He's rendering in Unreal and the unwrap and geometry aren't problems. If you look at "imported into ue4 and rotated" it's pretty simple geo.

Could you share your files? Preferably the high + low in case there are problems with the bake. Initially I'm not sure what the problem is! It may have something to do with normals getting messed up on export.

You're right. It is definitely a problem with the geo. I have the same weird lighting problem with a plain, unmapped lambert material. I'll mess with this some more after work today and post the files if the problem persists.

Bruno Afonseca said:

Are you exporting tangents or generating them in engine? Try both options

https://docs.unrealengine.com/latest/INT/Engine/Content/FBX/ImportOptions/index.html

I'll try that tonight. Thanks.

wetojo

@Bruno Afonseca  you were right!

Fixed it! UE4 was generating new tangents. I needed to import my tangents. Just a import option difference. No problem with my geo.  Thanks everybody.

AlecMoody

That shouldn't have happened with UE4 generating the tangents. You have other problems you should try to resolve instead of limiting yourself to only ever importing mesh tangents.

JedTheKrampus

Yeah can you please post the mesh and the texture so it can maybe get fixed?