You may already know whet ‘light painting’ is. It basically consists of a picture taken in dark spaces which captures the light by a moving lighted point, and draws a trail, like this picture that I took a while ago.
Many videos have been made by using this technique, frame by frame, such as this one, for instance. The fact that it is a freehand painting makes a rougher animation, though.
But in the video clip Silhouettes, by Floating Points, they have created a machine, some kind of 3D plotter, that leaves its light trail and is controlled by computer. Since it is a digital tool, one can see some pixelated areas.