facade generation

hi, i have some polysurfaces. how could i merge them into a solid so i can get the only outer surface of the union solid, to generate the facade.

i want to generate perforated screen facade by image sampler on the whole surface.

i know the algorithms to create perforated screen facade on a single surface (flat/curve), im just wondering is there any easy way to make an algorithm that can easily map the perforation onto every exterior surface of the breps..