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I have geometry being created through geometry nodes and I am am trying to flip the normals on this duplicate geometry. However, it appears that normals are a read only attribute in the geometry nodes. Any ideas on how I can flip normals through geometry nodes?

BenignBrett
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    It's not possible to modify mesh normals at the moment, but it's being talk about : https://devtalk.blender.org/t/geometry-nodes/16108/1519 – Gorgious May 31 '21 at 06:27
  • Has there been any discussion on when those might be implemented? – BenignBrett Jul 24 '21 at 19:07
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    It's not high priority right now it seems... You can follow the project tasks here : https://developer.blender.org/project/board/121/ – Gorgious Jul 24 '21 at 19:47

2 Answers2

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You can now use the Flip Faces node.

enter image description here

You can also plug a boolean field into the Selection input to selectively flip faces.

For example :

enter image description here

Gorgious
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It is possible to flip normals for any single face. You just have to do several steps:

  1. Detach selected face from mesh.
  2. Put this face into convex hull.
  3. Delete from convex hull all faces with normals orientation equal to normals orientation of the original face.

enter image description here

I already applied this solution in my answer here: Is extrude possible in Geometry Nodes?

3Dhedgehog
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