There's got to be more to it than that. Even with a really tight beam you'd run into all sorts of "Am I in the spotlight or not" problems, especially with the t

There's got to be more to it than that. Even with a really tight beam you'd run into all sorts of "Am I in the spotlight or not" problems, especially with the torch flailing around while someone dances (illuminance detected would be all over the place). Looking at this video https://www.youtube.com/watch?v=fYDSguhC4FQ https://www.youtube.com/watch?v=fYDSguhC4FQ It seems advanced patterns only turn up when people are in a roughly grid arrangement, and no one moves out of their spot except at predetermined times (obviously everyone is in on the choreography here). There are also dark periods after people finish moving around and "get in place". It looks like they are doing some degree of calibration. The torches my well have IR lights on them too that can be individually addressed to quickly calibrate every torches position, sorta like marco polo. Break it into quadrants and you could do it even quicker. It could be simply overhead IR lights, but gah, they are doing something really special to get those well defined sharp edges. Besides all that, everyone could just have assigned spots that they memorized. It's obvious they practiced, and arranging a bunch of people on a field quickly and fluidly is nothing new.