Mathematically, I believe the distance is determined by the limit of
“meaningful eye contact” according to Welles et al 2005. Therefore, the
maximum orgy perimeter is determined not just by distance, but by
eyesight and the topology of the orgy location. It’s not an orgy if
you’re in a brothel, mere feet from other people having sex, but
separated by a sound-dampening wall. Maintaining constant eye contact
with other orgy participants isn’t required, but the line-of-sight still
must be kept clear. For visually-impaired people, we can substitute an
aural boundary. For people who are both visually and hearing impaired, a
tactile and odor boundary would suffice.

Assuming an open space and everyone having 20/20 vision, an orgy cluster
would be maintained by the “nearest neighbor” standard. Johnson and
Plevis (2009) estimated the maximum distance that allows for “meaningful
eye contact” to be 25 feet during high-intensity sexual congress. You
could compose an orgy that circles the world as long as each node in the
orgy has a nearest neighbor that’s less than 25 feet away and with an
unobstructed view. Therefore, an orgy string requires 212 nodes per
mile. (A node can be a mating pair, a single masturbator, or any other
group that is physically engaged in sex). In order to span the
circumference of the globe, an orgy would require a minimum of 5,279,012
nodes, or about 11 million people given standard orgy nodal
preferences. I hope this answers your question.