This is the basic setup for our first round of photos. The camera is positioned overhead, looking almost straight down. The Dr Pepper can, our main subject, is visible to the camera through the narrow slit in the top of the box. As the box is pushed (in this view, from the right to the left), the can is free to roll on the carpet, but is kept in place by some cardboard and a wooden spoon. As the slit moves across the image, the can will roll in place under the slit. If the box moves at a reasonable speed, this should paint an unrolled image of the can onto a long exposure image. At least that's the idea.