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# 1 16-05-2012 , 11:30 AM
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Vray strange thing?

Okay, I'll try to describe it. Let's first imagine I have an object, and this object gets duplicated (mirrored) using 'duplicate special'.

(these could be chrome headlight rims for example, a situation where you would mirror the geometry.)

Now I apply a Vray mtl surface to both objects.

Now I render this simple set up and find that the duplicated object has a different look to the original.

And here's the funny part, if I reverse the normals on the duplicated object and then render, they will now both look correct.

Has anyone struck this anomaly?

It's got something to do with Vray materials, and duplicated mirrored geometry. If I just do a straight duplicate I will not get this problem, so it must have something to do with the flipped or reversed nature of the duplicated geometry.


Last edited by djwaterman; 16-05-2012 at 11:43 AM.
# 2 16-05-2012 , 12:14 PM
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Oh yes user added image

Jay explained it quite well:

Sometimes issues like this can also occur when you dupe an object and reverse it along a -x axiz or - z axis. When you freeze the transform Maya will warn you about negative faces. You need to go into the attribute Editor and turn off opposite. this will then cause the mesh to flip again and you'll need to again reverse the surface normals.


# 3 16-05-2012 , 12:43 PM
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Interesting. Can you put up the link to the original thread? I'd like to have a read.

# 4 16-05-2012 , 01:11 PM
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Also, I can't find 'opposite' in the attribute editor.

# 5 16-05-2012 , 01:33 PM
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Interesting. Can you put up the link to the original thread? I'd like to have a read.

https://simplymaya.com/forum/showthre...=36625&page=11

Also, I can't find 'opposite' in the attribute editor.

The first image is a simple cube where the left cube was created with using duplicate special with -1 across the x-axis.

The second image is the warning you get when you freeze transformations. Now the opposite attribute is set under Renderstats of the shape node.

You need to uncheck "Double sided", uncheck "Opposite" and then reset "Double sided". After this you will see your normals are reversed in the UV editor.

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# 6 17-05-2012 , 04:53 AM
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Thanks for going into detail. I will spend today's session getting to grips with this. It's quite a bothersome procedure isn't it, but I guess it makes some kind of sense, and once it becomes second nature won't be a problem. Thanks again.

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