UVs don't flip after mirroring geometry

Introduction to Maya - Rendering in Arnold

This course will look at the fundamentals of rendering in Arnold. We'll go through the different light types available, cameras, shaders, Arnold's render settings and finally how to split an image into render passes (AOV's), before we then reassemble it i

Watch

# 1 30-12-2013 , 05:59 PM

Registered User
Join Date: Apr 2011

Location: Dortmund, Germany

Posts: 229

hello. when i mirror geometry, UVs don't flip. they stay blue, but are not reversed. how can i reverse them? i need it for normal/displacement mapping.

Quote

# 2 30-12-2013 , 06:49 PM

Registered User
Join Date: Aug 2011

Location: Sliema Malta

Posts: 497

Here is a snap of the buttons to flip the UV's

Attached Thumbnails

Click image for larger version

Name: UVFlip.JPG
Views: 1953
Size: 42.4 KB
ID: 55201

Quote

# 3 30-12-2013 , 06:59 PM

Registered User
Join Date: Apr 2011

Location: Dortmund, Germany

Posts: 229

by flipping uvs using "flip" function the uvs turn red and normal/displacement maps don't work as intended.
i have one object with maps for it. now i need a mirrored copy of that object. when i just mirror it and use maps from the original object (uvs of the mirrored object are blue, but not mirrored), the rendered result is wrong.

Quote

# 4 30-12-2013 , 07:53 PM

Registered User
Join Date: Aug 2011

Location: Sliema Malta

Posts: 497

How about a pic of your UV layout and the rendered result. Notice how I gave a pic and within seconds you knew it was something else. Same holds true on your side for information. Otherwise I sit here and type all day...

Quote

# 5 30-12-2013 , 08:03 PM

Registered User
Join Date: Apr 2011

Location: Dortmund, Germany

Posts: 229

here's uv layout. it's same for original and mirrored objects.
second picture is the mirrored object with applied with displacement from original one.
last one is the original object with displacement.

Attached Thumbnails

Click image for larger version

Name: 1.jpg
Views: 1662
Size: 589.9 KB
ID: 55202

Click image for larger version

Name: 2.jpg
Views: 1531
Size: 69.6 KB
ID: 55203

Click image for larger version

Name: 3.jpg
Views: 1590
Size: 83.2 KB
ID: 55204

Quote

# 6 30-12-2013 , 08:20 PM

Technical Director
Join Date: Feb 2004

Posts: 2,988

That issue is caused by the normals not being flipped, not because of the UVs.

Imagination is more important than knowledge.

Quote

# 7 30-12-2013 , 08:27 PM

Registered User
Join Date: Apr 2011

Location: Dortmund, Germany

Posts: 229

oh, indeed. i though normals were alright, because "two-sided lighting" is off, but i didn't noticed i switched to viewport 2.0.

now i have additional question - how can i mirror an existing normal map for that case?

Last edited by mickhah; 30-12-2013 at 08:34 PM.

Quote

# 8 30-12-2013 , 10:25 PM

Registered User
Join Date: Apr 2011

Location: Dortmund, Germany

Posts: 229

i tried to invert green channel in photoshop, but got this result:

Attached Thumbnails

Click image for larger version

Name: 1.jpg
Views: 1544
Size: 19.9 KB
ID: 55205

Quote

# 9 30-12-2013 , 10:35 PM

Registered User
Join Date: Aug 2011

Location: Sliema Malta

Posts: 497

XNormal -y conversion. Game engines require the alt setting in some cases so I have to batch this out of Crazybump. That costs money. But XNormal is free and will do it as well.

Quote

# 10 30-12-2013 , 10:44 PM

Registered User
Join Date: Apr 2011

Location: Dortmund, Germany

Posts: 229

as i understood, i have to load high- and low-poly mesh into xnormal and switch +y to -y there. is there any way to invert already existing normal map, rather than render it anew?
i tried to export new map from zbrush with inverted green channel, but still have seams like in the last picture.

Last edited by mickhah; 30-12-2013 at 10:54 PM.

Quote