# Recalculate Outside - bad result

Hi!
I can’t solve this problem. When I choose: Mesh - Normals - Recalculate Outside then I get deformed surface of object (see pictures):

The picture before Recalculate Outside

The picture after Recalculate Outside

When I go wrong?

It’s easier to get help if you upload the .blend file. www.pasteall.org/blend can be used for this and one can share the link.

Normals recalculating in this way indicate bad mesh. Doubles could cause it which can be removed with select everything in edit mode and W -> remove doubles.

Non-manifold edges can cause it (doubles inherently are non-manifold but can be dealt with separately) those edges which are not connected to exactly 2 faces - this may include “internal” faces which cause the system not to be able to determine which is “outside” and which is “inside”

So take a good look at the mesh, remove doubles, inspect it in wireframe mode, and use the hotkey alt + ctrl + shift + M in edit mode to select non-manifold edges - this usually gives good indication where problem is.

Example, an internal face at the top of the handle, causes the very top edge to be connected to 3 faces, (the two on either side and the internal face) making it non-manifold, pinching the subsurf and casing normals to calculate incorrectly

I have selected non manifold edges (alt + ctrl + shift + M) and I’ve deleted vertices. Then I’ve used A and Ctrl + N (Recalculate Outside). It’s solved my problem.
This is the blend file:
http://www.pasteall.org/blend/19492

I think i found the problem, several part that lead into non manifold geometry
non manifold geometry will always puzzle the normal calculation.

They’re located there :

Close up on one :

Between the exterior of the model and the interior of that extruded hole, there are 2 faces, so there’s no possibility for the normal calculation to decide which side of those 2 faces should recieve which normal direction, which side is the interior and which side is the exterior for those faces.
And so when the normal calculation fail, it lead into a cascade of normal misdirection, leading into the black area artifacts.

To fix, remove those 3 faces

Then close the hole left

Now repeat for all the location i marked on the 1st screenshot, and a select all -> CTRL+N after that should re-order the normals correctly.

An alternative if you want to keep the extruded hole is instead of deleting the marked faces for each location, instead select this vertice

And delete it

Do this for each marked location, and select all -> CTRL+N will recalculate the normals without a problem

Thank you for your instructions. Now I understand exactly what’s going on!