Risa

I mean, you can have multiple people in the holodeck who are all out of sight of one another, so it's definitely capable of partitioning them off to display different environments to each.

It's unclear what the limits of this are, as most of the mass usage we see (e.g. when it's used for a wedding reception) has most of the participants clustered tightly enough that it wouldn't be necessary. But one of Quark's holosuites can accommodate an entire baseball team despite being much smaller than a Federation holodeck, so the actual required space per partition has got to be pretty small.