Faces with the same material and soften edges still do not render out as a single object

[i_am_fail]

I have a sphere that has the exact same lambert material on each face - but it is showing up like this with a clear line where some faces look like they have a different material or are treated as a separate collection of faces. It is all one mesh. I've tried deleting history, extracting and recombining the faces, nothing seems to get this to the original homogenous sphere it was like when you create a new sphere.

I'm using a sphere as an example, I know I can make a new sphere - I need to learn how to fix this for any object, does anyone know what's going on?

[_sebastian_f]

if the components along the "line" are detached you create a border edge between the 2 parts which breaks the vertex normals and by nature is a "hard" edge. you can see it if you turn on vertex normals in polygon display. to return to the original sphere´s shading you have to merge the vertices along the border (and soften edges) and not just combine the 2 parts or lock the normals before you detach them. last but not least you could try to transfer vertex normals from a reference sphere.

[i_am_fail]

Merging vertices and softening edges works for a sphere, but not in an actual model, for vector render mode, and I'm sure nobody on Earth knows why. So unfortunately this only fixes the test example I came up with, I still don't know what is causing shapes as simple as this to have hard edges when they are set to soft. Thanks for getting me 2/3 of the way there though, after literally months of not being able to figure out hardly anything myself. Extracting one face, recombining, will sometimes work - but sometimes the face I extracted remains hard edges after soften edges and everything as well so sometimes have to do it multiple times. Seems to be just a maya curse.

[i_am_fail · Accepted solution]

Actually a combination of what _sebastian_f god said and what I had been trying seems to work every time, it's just a pain in the butt:
Extract a face from the problematic mesh
Combine the newly extracted face back to the problematic mesh
Select the problematic mesh and merge vertices
Soften edges
fixed