perforating curved walls

[Anonymous]

i would like in one of my new projects to perforate some curved walls, not adding windows, i would just like to have some organic shaped wholes in them.
does anybody know how can this be done?
i've been reading forums and tutorials, but i haven't figured this one out.
thank you
i've attached a picture of something similar to what i would like to achieve, but on a curved surface

[Anonymous]

Take a look here.

The curves will add some complexities but the principal is the same.

[Anonymous]

thank you!