subsurf/smoothing problems

Sometime in my mesh i want a perfect smoothness so that you can not see the faces in the render. This can easily be obtained but sometimes it does not work well for what i want. Subsurf and smoothing both change the shape of the mesh making each face next to each other blend better. These results are not always what you want.

How can i make my mesh smooth so that the faces don’t appear in renders but the mesh still has it’s shape?

This question is a little confusing so if someone needs me to post pictures i will.

Ah ya a picture would be good to describe what you means with changing shape.

Of course does subsurf change the surface shape - it is the nature of it.
The more you increase the level the smoother the surface but the less drastic are
the surface shrinkage.

To state the obvious, if you haven’t clicked the set smooth button, do that. If you already have that activated, you could always crease the subsurf, though I’m not quite sure what you want without images.

Yeah I think creasing is what your after. Select a face and press shift + e and play around with that.

Or your model needs more loop cuts to help retain shape.