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I've been using blender for a while now - mainly just messing around. So all things being equal - this is a beginners question. (I tried searching, but only found the standard loop cut and slide questions)

If you take the default cube, and use loop-cuts to split it @ 50% (so all your faces are slit into 4 equal ones). Then if you grab a vertex in the middle of those 4 faces and move it perpendicular to the face (creating a pointed face) - why do some of the adjoining faces come out different than the others?

Either one of the two is OK with me, but i dislike that all equal faces do not have the same behavior.

Maybe someone can shed some light on this for me?

faces are bent faces are straight

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This is because you have created non-planar faces.

A non-planar face is a face with vertices which are not aligned in a plane in any direction.

Under the hood everything is represented in triangles (at least for drawing purposes), so blender must decide how to cut the quads. It can cut them two different ways:

enter image description here

Which way is used appears to be decided more or less at random.

To avoid this undefined behavior, you can split non-planar faces manually to match what you want (J works well for this). You can also press 3D view > Header > Clean up > Split non-planar faces to automatically split all non-planar faces automatically:

enter image description here

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  • $\begingroup$ And the answer is that simple ... thank you very much! $\endgroup$ – Frank Jackson Jan 22 '15 at 9:58

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