Add different options for drain holes

[gudvinr]

Is your feature request related to a problem? Please describe.

I have a model that has slot in it that can be used as drain hole but it is rectangular and not round so you can't use round drill without ruining its shape.

Describe the solution you'd like
Add an option to create drain holes using automatic boundary search similar to smart support placement for FDM.

Describe how it would work
You select surface inside cavity and then it is used as normal to create hole through hollowed shell.

Describe alternatives you've considered

Another option is to add some kind of modifier with arbitrary shape (similar to modifiers/negative volumes/support blockers in FDM). It makes this harder to use in this particular case or in any case where you might need complex shape. But at the same time it will be useful in cases where you don't have cavity to safely find boundaries.

[Efroymson]

I came here to make this feature request, or one very like it. The only addition I would make is that I use FDM printers, and need to make hollow prints for casting. They are often "tubes" so it would be great if certain faces could be identified as openings, and not filled in.

Current workaround I am trying is to enlarge model by adding material to certain faces, hollowing it, then placing it on the faces that need to be opened and cutting them off. It is not so easy to do this, however.