Asked • 03/18/19

Walking around someone who is moving in Slow Motion?

In the "Buffy the Vampire Slayer" series musical episode, "Once More With Feeling", during the Giles and Buffy fight montage (Song: 'Standing in the Way') there is a scene where Buffy is hitting a punching bag in slow motion. Giles in regular speed is singing, he walks in front of her and then behind her.I can understand how one layer is through a green screen. I'm not entirely sure how it worked for two layers in real time. Can anyone give a quick synopses how this worked?

Kelly M.

These types of shots are done using repeatable move, motion control camera/heads. I used to do this kind of work. The motion of the camera using heading and pitch control wheels drives a robotic camera head. This motion is recorded by a computer system attached to the wheels. They do the first pass at normal speed, and then record with the second pass with the camera motion at half or 1/3rd and the actor that is present at the second time around, hits their marks and in frame working with a VFX on-set motioncontrol assist unit which can play back both passes directly over each other in real time. I did this for a few years using the NewTek VT2 (PC version of the original toaster that came out on PC in 2000)), a NewTek SX-8 and a dual xeon computer that was adapted to work on set and be quiet. The motion control process was triggered using what are known as GPI singals or general purpose interface triggers. Motion record start was triggered by a "blip" in the VT-Edit timeline that threw a switch to start the motion control system on the playback+recording pass (typically the second) and was the resulting material was pulled back in, mixed in real time and played out to the director or VFX people on set under 30 seconds. Totally unheard of even today.


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