[BLENDER] Select faces based on face orientation?

I find it wierd that with this face orientation feature, there isn’t a way to select all the red faces so u can flip the normals. Maybe an addon or script that can help with selecting all red faces or faces with opposite orientation? I have tried Recalculate outside for Normals. Doesn’t work for very complex meshes. This would be useful especially especially before exporting to game engines.

I am using image for demonstration purposes. Appreciate any info anyone can share.

See if this helps you. Select a face first
Need to run it a couple of times though for complex geometry.

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Thank u ramboblender.Didn’t work unfortunately. Imagine a complex house with lots of shapes for roof windows, shutters e.tc. with messed up normals. The script kept flipping way more red a number of tmes then more blue after.

You right it works in organic shapes better.

It is because there is no red or blue face for blender. Blender is displaying red or blue sides for all faces according normals.
If Recalculate Normals Outside does not work, there is no reason to expect a select operator doing a better job.

At least, Recalculate Normals Outside should give a satisfying result for most of faces when the whole mesh is selected.
Then, for problematic parts, you should be able to select several faces at once, using the large variety of selection tools (shift G > similar normal or coplanar, Select Linked Flat Faces).
And after few steps, you should obtain correct result by flipping them.

Anyways, you should not have to do it face by face.

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If recalculate doesn’t work, there is probably some underlying problem in the mesh. Like double edges, loose faces, nonmerged vertices, manifold issues etc. Do you have an example of such a mesh you can share?

I will check that. Unfortunately I can’t share the model that is being problematic. If u could download any house model with roofs, windows and try it, that would be awesome

Tried the other options before making this post, none really worked. Had to do it face by face and they are a lot.

Hi

  1. Select a red face
  2. Menu Select > Similar > Normal
  3. Press Alt + N > Flip

Nah…Didn’t work. Also selected blue faces as well.

Select Similar Normal is selecting red faces on one side of cube and blue faces with same normal on the other side.
So, in that case, that does not work.
But if you select one red face per side of cube and use Select Similar > Co-planar, it should work.

If you hide back faces of your mesh, you should be able to use Select Similar Normal.
You just have to make a pertinent hiding to use pertinent select tool.
There is no reason to not being able to treat a complex mesh by parts.