Reflection in sphere becomes more distorted as subsurf increases?

Question

I was baking normals from hi poly to low poly meshes. With this specific example of a hi poly icosphere the reflections are distorted, whereas the low poly sphere is less so.

so i was just wondering;

• why does this happen?
• how may it be fixed?

note - A subsurf modifier was used on the hi poly sphere. Applying the modifier makes no visible difference.

I don't think this will be much of a problem in most cases but i was just curious as to why this happens, since in my head it would make sense that a higher poly mesh would be smoother than the low poly mesh. However in my experiment the opposite is true.

Thank You

Answer 1

Even if the Ico sphere has a nice distribution of triangles it isn't the best topology for normals. Worse is that it subdivides very bad since it is all triangles. The results gets worse since the frequency of the subdivision pinches increases.

The UV sphere gives better result but you get pinching deformations at the poles since they are triangles.

To get the best possible result for subdivision use a subdivided cube and add a Cast Modifier (cast type "Sphere") to get it to be a sphere. This creates an all quad topology with only 8 3-edge poles.

To further improve the normals you can add an Edit Normals Modifier set to Radial and enable Auto Smooth in the Mesh properties. Now the normals will go straight out from the centre of the Sphere.