Normal edit modifier produces jagged edged renderings in 2.77 #48576

System Information
Windows 10 Pro, Nvidia GTX 660

Blender Version
Broken: (example: 2.77.1 11b0874)
Worked: (in 2.76 various versions)

Short description of error
When applying the normal edit modifier when rendering in Blender Internal it produces a jagged edge where the normal edit modifier has been applied. There is also a weird view in the viewport but I could not reproduce this in the startup file. See images

the jaw line has the jagged edge:

See the facebook post for things we already tried to counter this effect:
https://www.facebook.com/groups/BNPRandFreestyle/permalink/1180238755332559/

Exact steps for others to reproduce the error
this could also be reproduced by using a start up file of susanne and applying the normal edit without any material applied to it.
normaleditmodifier.blend

Changed status to: 'Open'

Added subscriber: @WasiliNovratidis-1

Added subscriber: @mont29

This is not a bug actually. Issue here is that your are pushing normals way out of the 'safe area', making many of them reversed compared to default ones (computed from neighbor face normals).

Up till 2.76, Blender did not handle correctly that 'inversion of normals', leaving face normals opposed to its vertices ones, which was really bad and inconsistent. Since 2.77, winding of such faces is now reversed, to make face normal match the direction of its vertices ones.

In your example .blend, several faces are 'reversed' that way, producing the black patches. I’ll commit soon a new setting to the modifier allowing to limit the maximum angle between original and new normals, keeping this below 90° should help prevent most of those face normals inversions.

Editing normals in such an aggressive way also raises another issue, present since the beginning, which is it makes the terminator problem much more visible. Nothing to be done here really, you have to handle it yourself I’m afraid.

Changed status from 'Open' to: 'Archived'

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Normal edit modifier produces jagged edged renderings in 2.77 #48576