restricting photon bounces to an area

[plastic_]

it would be cool if you could restrict the photon bouncing to a specific area. i'm thinking about an athmospheric bounding-box dummy, for example.
or maybe some attenuation setting for photons in the light.

like i have a big building and only want to render a specific part of it from the inside, say the entry hall. bounces for the sun are calculated for the whole geometry, which is slow and takes much memory.

[losbellos]

you can limit the memory usage with the max photons settings (higher makes less memory used) You can also focus with the light settings some, I think. For example if u use directional light then make the parameters that it covers only that part you need. Okay there will be some overlapping but at least something.
Otherwise I dont know, it wouldn be easy, because then how to cover the openings? If a photon reaches the bounding volume how it will bounce back?> Should it have some material, etc. Maybe if you simply just close the "shop" with some planes.