Instances - duplicate special reversing normals

[heatherwrightart]

Hi, help always appreciated, I'm a new user.  Looking to figure out duplicate special instances and how scaling an object (to flip it) affects the normals (Using Maya 2015, Student Ed, MacBook Pro OSX 10.9.2).

PROBLEM:  When I duplicate special, and duplicate the object in an instance but the object is flipped, the normals are reversed.  I can select the instance and reverse the normals BUT this then reverses the normals on the parent object.  This affects what happens when I want to texture the model.

VISUAL:  See picture - the right eye brow is an instance of the left - the normals are reversed (it's black).  If I reverse the normals of the right eye brow, then the left eye brow reverses it's normals and goes black.  Same thing on the hands.  I want all the normals pointing in the right direction so the objects can be textured, but I only want to texture the parent, and have the instance copy that texture too.

[hazlipa]

Hi heatherwrightart, cool model!!

Looks like there may be a few things going on. You mentioned the object is flipped, but it seems right in your image. But, in case you do duplicate special and it is upside down, or the wrong orientation, you can change this in the duplicate special menu. You should see either 1, or -1 for the 3 axis (x, y, z) You may need to change these until it's facing the right way. 

As for the normals, have your menu set to "Polygons" then go to Normals > Conform, then if needed, Reverse. 

And for the UV's, I believe it is on by default to duplicate, but you may have an option to change this in the duplicate special menu. I might be able to better tell what's going on with the UV's if you could throw a UV map texture on. (You can find them online, they're checkered in colors, and numbers so you can see if the UV is upside down!)

Hope this helps! Let us know if you still have questions!

[heatherwrightart]

Hi,

Thanks for your input.  I wanted both the hand and the eyebrow geometry to be "flipped" (i.e., I made the right hand, and wanted to copy an instance of it, but flip it, to create the left hand.  same with the eye brow).  That's not the problem.

There are a two problems happening here:

1.  Whenever I use UV editor on a new part of the model, TWO UV sets show up.  So I see UV set 1 and UV set 11.  And I can't delete the second unwanted one (UV set 11).  For some reason the unwanted set always seems to be called UV 11.  What is frustrating is that the texture shows up in UV set 11, but not in UV 1, the default location, where I need the texture!

2.  The duplicate special instance is causing me a problem too.  I am using duplicate special to create an instance.  I am using the scale (-1) to purposely flip the model (so that the right hand becomes corretly oriented to become a left hand).  When I do this scaling, the instance shows up with the normals flipped.  If I select it, and reverse the normals, the parent instance's normals get flipped.  I tried conform, as suggested, it doesn't seem to do much -- certainly doesn't fix the fact that I have a parent and an instance of it, but one of them has flipped normals (showing black in the model window).

[staticmut84]

I'm getting the same issue. When I go to "Duplicate Special" and flip the instance along one of the axis's the normals get flipped in the instance. When I go to Normals > Conform and then try to reverse the normals on the instance, the normals on the parent switch as well. Same when I try to flip the normals on the parent, the instance changes with it. I never had this problem with 2014. Is there a way to correct this issue?

[TrajanHunter]

My work has come to a complete stop because of this issue. I can't continue as easily without viewing the whole image of the part I'm working on, and if I just mirror it, it won't be an instance that will be the same as the original if I need to modify it. I'm not sure why there is even a reason to have maya 2015 flip the normals when duplicating special, but it isn't helping me progess in the least. Any help anyone can suggest will be appreciated.

[pshwayka]

Hi TrajanHunter,

Does this happen every time you Duplicate Special as an instance?  I can't reproduce the problem...If you make a simple scene with a polygon primitive and Duplicate Special as an instance, do the normals get flipped?

[TrajanHunter]

Every time. I can't seem to be able to change the faces without flipping
them to the wrong side on the original too.

--

Sincerely,

T
​rajanHunter

[pshwayka]

That's odd.  Here's a scene where I created a sphere, assigned a material to it, moved it to the right along the X axis, snapped the pivot back to the xyz origin, and did a "duplicate special" with the settings shown.  I also turned on the face normals on the instance to show that they are pointed in the correct direction.  It sounds like you're saying that this test would not have the same results for you...correct?

[TrajanHunter]

Now this is strange. I repeated the same process as you did, but still got the same result. The skin material is on the opposite side of the faces. The strange part is that when I turned on the face normals, they were pointing in the correct direction. Are you using Maya 2015? From other reports, this version seems to be the only one having this issue.

[pshwayka]

Hi TrajanHunter,

Sorry for the delay...I missed your reply the other day.  Yes...I did this test under Maya 2015 Extension 1 SP5 under OS X Yosemite.

[TrajanHunter]

I noticed recently that sometimes when I duplicate special, it would work fine as an instance. But then if I duplicated either of the 2 pieces agian in a different direction, the faces suddenly flip on the first copy. It makes it real hard to figure out what is even going on.

[pshwayka]

That is indeed odd.  I just tried what you are describing, and all the faces were fine on the original and all the copies...

[TrajanHunter]

I may have just found a "cheat" for this glitch that brings me great
relief. I tried giving a different color or texture in the past to see if
that changed any thing (which it hadn't). After I duplicated my object the
way I had wanted, this time I selected all the pieces and used the 'assign
new material' from the right-click drop menu, and selected Phong E (not
sure if Phong E is important to the cheat or not). All of the faces were
suddenly displayed in the proper direction. Then I undid the 'assign new
material' I just did, and it went back to the default shading, but
continued to keep the proper faces. No idea why this happens, but it
worked. Thanks so much for bearing with me for my problem.

[TrajanHunter]

One downside to this "cheat" however, is that you will have to do this every time you open your project each time you open maya. I don't know how this would effect whatever it is you intend to use your item for if this happens to anyone else, but I may leave a message when I finish my project saying how it came out.

[mcraig]

If duplicate special reverses normals for some reason, I just set my viewport to legacy.

[antinoo.carlos]

Go to Modify Menu. On Freeze Transformations, set Lock normals to Never. Both original object and instance will have normals in the same direction.

[TrajanHunter]

It was always set to that for me. For some reason it still doesn't work.

[TrajanHunter]

When done on my project, it does fix it, but after saving and loading the project into maya again, it is messed up again. It would need to be done every time you start again.

[antinoo.carlos]

You can try a different approach by going to Mesh Menu, Mirror the geometry in -X axis, and then use the simmetry mode set to World so you can tweek the model in both sides simultaneously. Hope it helps!

[sketchgoatee]

So, I have been having the same problem, and I've found an annoying but otherwise good workaround to help out.

Reverse normals until all 'blacked out' objects appear correct, then export the items and re-import them.

I was working on a robot  and found the armour plates were annoying me when half of them would be black and the rest displaying the default lambert shader. Reversing the normals would work for the time being but then regardless of save, they would revert to their messed-up-state the next time I opened the file. Yes, I should be working on just one side then mirror it, but I've been having a great deal of trouble getting mirroring to work right, so I do it the more polygon-intensive way by just duplicating, throwing a '-' in front of the Translate & Scale X values (and sometimes the occasional rotate Z) and reversing the normals from the now blacked-out object.

I've restarted the program multiple times now and the computer as a whole, and the export trick seems to have worked for me. Hopefully it works for others that have had this problem. That said, the real test will be taking it to the computers at Uni and seeing if they have issues as well given part of my problem may have been working with the student edition at home (Mac) and then using the Pro Edition there (PC).

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