/vt/ - Virtual Youtubers

>>10960999
If it wasn't a computer generated space, you would simply record the scene twice with out moving the camera and merge the images afterwards. The same actor can be on the left or right side. This only works well, if you have full control on the scene especially the lighting of the scene, because otherwise you would see the seam between both scenes.
In case of the concert, you have the full control over the scene, but it's completely irrelevant here since the whole show takes place in a virtual space.
Either Kuro or Shirakami sang and danced first and then they did the same with the other character. Just keep in mind, that the cameras are used to track the active markers which are placed all over the actors body. The output is motion data, so basically data about where every marker was at a time. You map it on a skeleton and give it skin and as result you'll get a 3D character with realistic human movement - in t his case dancing.
The stage is probably something the Unity engine would call "level" and if you insert the two recordings and synchronize them, you'll receive the outcome we saw.
I guess out of convenience they also used the audio from the recording to avoid having lip sync issues and the microphones they use seem to be fine for that. It should be pretty easy for a singer to keep the same beat for a song. If you watch some compilations where different holos sang the same song, you can see, that they their singing overlaps perfectly fine unless someone adds some talk or so into the song.
Of course, you could have simply played the scene with another actor, but watch the complete show again and keep an eye about where the characters are standing. Los! Los! Los! was the only song, where nobody walks around and they spared out any interaction between the characters. The guests where moving around a lot and when Fubuki was alone, she walked around.
Motion capturing is an interesting technology and there are many behind the scenes videos on Youtube explaining and showing how acting in today's film industry works.
tl;dr version: >>10961250