Topology question (square hole in cylinder) I have a cylindric shaped mesh with two faces that has been extruded into the cylinder. I am using subsurf and the extruded part is naturally curved due to the subsurf. 
I need the extruded part to be almost 100% cubic and not curved. I know i am probably doing this wrong but right now i dont know any other way.
Creasing doesnt give a decent result so that is out of the question. Model it another way? Interesting but how?
Or maybe there is a solution to my problem?

I have added a screenshot to ilustrate.
This kind of topology will work fine for a 16 vertex cylinder, a bit more complicated for a 12 vertex cylinder:



There's a trick to avoid pinching with the Shrinkwrap modifier:

Create a cylinder at the exact same place and with the exact same diameter. Hide it.



On your original cylinder, create a vertex group around the square hole.



Give your cylinder a Shrinkwrap modifier with the hidden cylinder as Target and Vertex Group > Choose the group you've created.