Smoothness and mental ray in Maya

Question

When I create a polygon, there are three quality display settings in Maya: rough, medium and smooth. What is the use of these display qualities in realtime and what does smoothness really indicates? I mean: is it actual object that is shown after rendering is done and why does a polygon looks like a disoriented sphere, when I press 3? My friend suggested to use insert edge loop tool to make look like a sphere, is this the right process?

What is the difference between the above and below image and should I make the bottom image look like a smooth square with the insert edge tool before I start working on it?

Answer 1

Smooth Mesh Preview has three modes (by pressing the 1 (the image above), 2 (Cage + Smooth Mesh), or 3 (the image below) keys). You can quickly see how the model will appear when smoothed with not as many polygons (Try to use Mesh > Smooth and you will find the difference).

The approximation (Math - split and average of connected points if I am correct) happens between the points so dividing the edge by the insert edge loop tool works. In the case of the cube you can find Edit Mesh > Bevel useful too. There is one another method to make it less or more smooth without increasing the resolution of the mesh. Mesh Tools > Crease Tool.

When you are happy with the model you can keep the Smooth Mesh Preview if you are rendering in Mental ray. For other renderers and softwares you can convert it by Modify > Convert > Smooth Mesh Preview to Polygons.

Answer 2

Above is Poly model, and below image is Sub-div(sub division) smooth.

a sub-div model has the same amount of Polyface but smoother.