[feature request] Generate brim for small parts only

[oscahie]

I'm printing this elephant (http://www.thingiverse.com/thing:257911) and had some issues with the adhesion to the bed. Using a wide enough brim solves the problem, but obviously degrades the final print quality, since removing the brim from the legs and other parts is tricky, and will leave visible marks. So I was thinking, why is a brim generated for every part when it's actually only needed for the small ones (i.e. with small contact surface)? I think that there should be an option to only generate a brim for perimeters smaller than X mm, or something like that.

[whosawhatsis]

Duplicate of #1316

[alranel]

Yeah. Thanks @whosawhatsis. Let's follow up there.