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This is done by shining bright Infra Red lights high in the stadium down onto the crowd. We cannot see Infra Red light ourselves, but the lights/torches the cro

This is done by shining bright Infra Red lights high in the stadium down onto the crowd. We cannot see Infra Red light ourselves, but the lights/torches the crowd holds can detect the infra red light and respond when they see it by switching on and showing visible light we can see. Thus all the lights the crowd have can be commanded to light up at the same time, or turn off at the same time. In advanced situations the infra red lights can trigger mass synced colour changes in the lights the crowd holds, exactly the same way an infra red remote control commands a TV to do different things. Cheap and effective tech.

Itsdijital 10y ago
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.

Itsdijital 10y ago

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.