After I joined together a mirrored joined duplicate into one single mesh, the duplicated mesh becomes purple:

Before and after

What is going on here? Do I need to be worried about this? When joining the roof with the base of the building, this doesn't happen.

  • $\begingroup$ where is the purple ( usually a missing texture ) ? $\endgroup$
    – Chebhou
    Apr 25, 2015 at 13:05
  • $\begingroup$ The whole other half of the roof becomes purple, it's pretty easy to see in the picture. $\endgroup$ Apr 25, 2015 at 13:05
  • 2
    $\begingroup$ try "Recalculate Normals" "Ctrl+N" in edit mode, (still can't see the purple) $\endgroup$
    – Chebhou
    Apr 25, 2015 at 13:07
  • $\begingroup$ there are related answers to this question, but I can't find the question as being asked this way anywhere: but related: blender.stackexchange.com/questions/3606/… $\endgroup$
    – zeffii
    Apr 25, 2015 at 13:45
  • $\begingroup$ @Chebhou It's... well maybe it's not purple, perhaps it's more like dark grey. $\endgroup$ Apr 30, 2015 at 14:03

1 Answer 1


The difference in face colours is an indicator that the direction of those faces are not uniform.

enter image description here

Enter edit mode and look for the side panel submenu called "Mesh Display"

enter image description here

In the normals subheading, select the face icon. Lines (called normals) will start to emit from each face. I've adjusted the size slider so those lines aren't ridiculously large or small. The thing to note here is that if you don't see the line emitting from some faces, that those faces are flipped.

To make them uniform press cltr+F to get the faces menu and Recalc normals (Or Directly using Ctrl+N)

This makes the mesh faces point in a uniform way, and the colour difference will go away:

enter image description here

  • $\begingroup$ Thank you, I figured out that I had to flip normals myself before your answer appeared. I have still marked it as it's the right answer =) $\endgroup$ Apr 30, 2015 at 14:02

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