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In the image I have 2 cubes. One has loop cuts and with shade smooth it looks much better.
Looking at the normal direction then both cubes are the same. Does the one with the additional cuts work better because the surface area of the faces is smaller at the 90 degree edge?
thank you
I would say it this way, I hope I’m accurate and clear:
Smooth shading creates a gradient between the faces of your object in order to fake a smooth surface. But you have to keep in mind that a face is always made of 2 triangles, so actually the gradient happens between these 2 triangles, and between these triangles and each triangle of all the adjacent faces.
On a complex object and when the angles between the faces are increasing, the gradients will inevitably begin to create some triangulation artefacts (see pictures below).
If you add some edge loops close to the angles, the main face has now a new adjacent face that is on the exact same flat plane, so you won’t risk anymore artefacts. It will happen on the new additional faces though, but as they are very thin you won’t see it.
By smoothing normal direction is overriding by 'fake' normals which interpolated from surface area between edges.
There are detailed answered questions, one of them How to smooth shade an object while retaining hard edges?
And a little bit of theory Normals, Vertex Normals and Facing Ratio
