Why is Union Subdividing objects? When I try to Unionize two objects the one that is outlined in red before I Union them. Once Unionized is smoothed as if I had upped the view on the Subsurface Modifier. I am using Blender v2.79 and I have a Subsurface Modifier on both of the objects at view 2 and render 2 and a Mirror modifier on both objects with it on the basic set up. I can only figure out how to add one picture so I put the one with the end result.![ this is the problem the top set are more Subdivided and I can't figure out why
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When you join object A to object B the modifiers of object A are NOT applied, and just get deleted, but the modifiers of object B stay the same and therefore are influencing object A once joined.

For this reason modifiers should usually be applied before joining objects.

On the other hand smooth and flat shading shouldn't change since this kind of data is attached to faces rather than the whole object.