I'm not 100% if this is caused by normals,
I'm using 3ds Max 2011 and I have some really crazy problems going on.
I started with this low poly mesh:
I UV'd it in Headus UV layout
I worked on the high poly in ZBrush but this particular model didn't end up there, I intended to bake down.
I decided that I didn't need most of the little grooves and indentations and that a normal map would be sufficient so I converted to editable poly and tried to remove them, when I started removing them I got this result:
It looks like the smoothing groups are different but that entire row plus the rows above and below are set to 4.
The weirder part is when I undo this it gives me an even crazier result:
I'm honestly not sure what's causing this, things I've tried:
Checking Polygon Smoothing Groups (several times),
Putting a Normal modifier on and unifying/flipping and checking etc.
I've also tried resetting UV's and even an older version of my model before UVing in case Headus was the culprit.
Furthermore the OBJ exports with this problem as well so it doesn't seem to be Max specific it might be my geometry.
However, my friend who had access to this model managed to do the same thing I was attempting without any issues, so could my Max version be bugged?
If not does anyone have any explanations for why this might be happening?
Tried in Max 2014 student too, same problem so I assume it's my geo although with the amount of problems I've been having I'm starting to warm to the idea of starting again, it's currently halting me at the moment