How to make a smooth oval window Here is a simple model that I'm working on:



I want to make the selected ring of edges smooth, to get rid of the discrete angles and get an oval shape. Something like this:



I have tried applying subdiv modifier but that changes its shape to a multi-point star. Also it smooths outer edge of the cube too, which I do not want. I have also tried Ctrl + R, but that does work on the selected face, only on the outer faces. Lastly I have tried Alt + Shift + S, which only changes the size of this face but doesn't do the smoothing that I want.
You need a combination of Subsurf Modifier, Smooth shading and Edge Crease



Start wit a plane.

Subdivide it.

Select some vertices to create the outline of the window.

Press Alt+Shift+S (to activate the "To Sphere" tool)

Move the mouse a bit to create a rough oval.

Add the middle vertices to the selection and extrude the shape of the window.

Press &#9096; Ctrl+2 to add a subsurf modifier with two subdivisions.

In edit mode set the object to smooth shading.

To make the outside edges sharp, enter edit mode, select the vertices on the edge of the object and mark a crease (Shift+E) with a value of 1, so that the edges are sharp.