Another possible way to achieve this shape is to use actual curves.
In Object mode Shift + A and add a new Bezier Curve. Enter its Edit mode, pressShift + Tab and set snaping mode to Vertex; select one of curve vertices and grab it, hovering your mouse over vertex in the corner of your base mesh:
Do the same with another vertex of the curve and turn off vertex snapping (again Shift+Tab). Now to setup curve shape begin rotating and scaling its vertices
along X
or Y
axis (depends on your scene) to get desired form:
After converting it to mesh, enter Edit mode select all vertices and extrude upwards. With extruded vertices still selected scale them to 0 by Z
axis. Now again turn on Shift + Tab and grab extruded vertices, they will align with top corner of the base mesh. Select all, W > Remove doubles. The result can look like this:
With everything selected, press E and this time choose axis to extrude along the base mesh.
After extruding, setting Shading to Smooth and adding Edge Split modifier the result will look similar to this:
The advantage of this approach is that you can create pretty much any shape of the corner by simply editing the curve in the beginning.