Problems with modelling a girl's head

Hi everyone,
I am trying to model a girl’s head. I think it went well until I reached the neck. Now, everytime I smoothshade the model, she has this horrible crease at her neck region. I can’t understand why this is happening. To the best of my knowledge, the topology looks ok in subsurf. It’s only when I set the shading to smooth, as opposed to flat, that this is happening. Can you help me? I’ve attached the blendfile as well.
Thanks in advance!


girlheadlater.blend (432 KB)

Tab into Edit Mode. Select all (A key). Hit CTRL-N to recalculate the normals. Done.

Wow, that was superquick! Thanks a lot, yes, it works! What exactly was I doing wrong?

That’s not necessarily your fault…

Despite the fact that Blender displays polygons as opaque from the front and the back side, they’re still only single sided objects. The so called “face normal” vector indicates which side is the front (that should point to the outside of the model… ). When in Edit Mode, Blender has the option to display the normal vectors as tiny cyan lines.

During polygon modeling sessions it can happen that Blender gets confused about the orientation of that normal vectors, leading to polygons facing front being directly connected to polygons facing back: This will give those harsh shading artefacts, as the mesh literally gets flipped inside out at that point. CTRL-N forces Blender to re-evaluate the normals’ orientation based on the entire mesh structure.

Thanks Ikari, for your detailed response!
I shall keep this in mind from now on. One always learns something new everyday.
Thanks a lot again for your quick response!

And thanks a lot to JA12 as well, for pointing me out those forum posts!