I would like to preface that by subdivide, I mean the one that merely adds more polygons inside a mesh without distorting a shape, this:
Now from what I do know about smooth-shading, when a pixel is shaded, the normal used for shading that pixel is an interpolated value of the vertex normals of the vertices that make up the triangle the pixel is part of
However, I noted that a smooth shaded cube for instance without any subdivisions looks like this:
This is understandable
However, for a subdivided cube:
A picture in object mode for more clarity:
This does not make sense. Why should it look any different than a normal unsubdivided cube? Let's take some point on the 2nd cube containing a new vertex as a result of subdivision, say here:
Let's call that point, point P. This point P has some normal Np. If we were to look at that exact point, but on the first cube instead, since the normals are linearly interpolated, the normal at that point on the first cube would be exactly identical to the normal Np in the second cube
Following the same logic, every other vertex normal on the second cube should be identical to the normals at those exact points on the first cube, generated by interpolation of vertex normals.
As such, lighting should logically remain identical on both cubes, but as we can see, there are differences in how both meshes look. Precisely what is causing both of these meshes to look different?
Shouldn't the normals at every point on both cubes be identical, since after all, there has been NO surface deformation of any kind, and since linearly interpolated normals provide a perfect accurate normal per pixel on a triangle/polygon atleast on a flat surface like that of a cube's?