Maya 2013 - Shading Errors when combining meshes

Slave_zero

Hey folks,

I recently dug out an already completed model of mine for portfolio update purpose.

I saw that the export-model had some strange shading issues compared to the not-combined model I used for setting up my bake and other stuff.
I tried to get my head arround this issue and discovered that as soon as I combine both meshes the mesh normals / mesh smoothing seems to change. (see screenshots)

Up to now I've found no way to get the combined model use the same shading / normals as the seperated meshes. This behaviour is extremely strange as I used a script for creating the smooting groups along the uv-seam.

If anyone has an explanation for this I would be very happy, because I've used combining / seperating meshes a lot, especially in earlier maya-versions and I want to know why this is happening.

Here are some things I have already tried / some facts that might be helpfull:

- changing smoothing on the uncombined model and reapplying my script works fine
- bakes were completely done on a triangulated model, the issue is exactly the same on triangulated or quad-model
- I used set to face, conform and average normals to get rid of any normal-issues on my uncombined meshes, I reapplied my smoothing script and my shading is fine. I did exactly the same with the combined mesh, but the shading issues are still present
- I tried to combine one of the meshes with a newly created cube - same issue

I'd appreciate any suggestions on this problem, thank you.


These first two shots show how my model is supposed to look like:




These two shots show the shading errors I have after combining the two meshes:

chronic

didn't maya 2013 introduce angle weighted mesh normals as default? i cant find the documentation but here it is for 2014. you should change it to 'unweighted' to match what you had in other versions of maya - and hense what you baked your normals with.

http://download.autodesk.com/global/docs/maya2014/en_us/index.html?url=files/GUID-232E99F8-96B4-4870-8BA0-4887C1C8F0F2.htm,topicNumber=d30e185461

when you import a mesh into maya 2013-14 from an older version it should preserve the normals by locking them - when you combine with another mesh it'll re-evaluate the normals and switch to the angle weighted methods.

Slave_zero

Thank you for this information! I've looked into this and it really seems that this is the problem.
Problem is maya 2013 doesn't have an option to changed the weighted normals method in preference window. Seems they've added this for 2014.

On the other hand the documentation is saying that in case you are unlocking normals maya will automaticly use its default normal calculation method. So I would expect my uncombined mesh to experience the issue when just performing an unlock. But the opposite is the case. Performing an unlock sesults in shading changes but those can easily reverted with the smoothing script.

strange. Anyway I'll try to dig deeper into maya 2013 documentation.

Update: I've found the option to switch weighted normal method in maya2013:

Attribute-Editor > myObjectShape-tab > Mesh-Controls

St.Sabath

You could try locking your normals before combining the meshes..

Slave_zero

Thanks for the suggestion. Actually I did try this as well but it didn't solve my problem. It seems that maya treats any new created object with the standard weighted normals calculation. And I think combining two meshes always leads to the new object to be treated as an entire new object, even if you don't delete history.

Anyway to solve this kind of problems after combining your meshes, you only have to switch the normal-calculation to unweighted in the mesh-control section of the attribute editor. This works just fine.

Although its a pain that there seems no option to disable this feature in preferences on a global basis. This seems only available in maya 2014.

VeeJayZee

It happens to me ocationally whenever I switch back and forth between Maya 2009 and 2011 (its a workflow thing ^_^) What I usually do is I export the two problem geometry to OBJ with the Normals and Smoothing turned on in the options the import it the Maya version I'm going to work on.

Justin DeVore

Thank goodness for this thread! I've been working on a set of simple modular walls that are supposed to line up precisely with each other's edges without showing any shading indications that they're not just one continuous piece. The straight sections all worked fine, but as soon as would create a corner piece the shading would fall apart. Knowing about this option quickly fixed all that. Thank you!