DMM can't generate from a Duplicate Special Mesh. What to do?

[findamir]

Hi, so I am modeling a bench and I decided for the arm, to duplicate the other arm and flip it via "Duplicate Special Option" and do a "Scale: -1.000" for the X plane. But the flipped arm won't work.

I tried to freeze transformation and erase the history by type, but nothing worked.
So once I duplicate something with a -1 scale, what should I do to make it DMM verifiable?

Image shows after I press create DMM on the duplicate piece.

Capture.JPG

[findamir]

I found the answer. DMM started not working properly. Even to the point of making a cube and extruding once. I deleted the "preferences" and made it prefOld folder, restarted Maya and all was working fine. I was about to lose my head. I left this up in case people ever come across a problem like me, instead of deleting this post.

[mandark1011]

another possible and most likely reason for this is that by duplicating an object into a - scale space you flip the normals to the inside of the mesh. I suggest turning two sided lighting off in the Lighting drop down menu, when your object turns black it means the normal are reversed. DMM will not calculate reversed normals.

[findamir]

another possible and most likely reason for this is that by duplicating an object into a - scale space you flip the normals to the inside of the mesh. I suggest turning two sided lighting off in the Lighting drop down menu, when your object turns black it means the normal are reversed. DMM will not calculate reversed normals.

Thanks for your thoughts and that is definitely a reason for DMM not to work. That was one of the few things I did but it still was not a helpful outcome. deleting the prefs definitely solved my issue, I just can't understand why.