Painting under the camera
A glass plate is placed under a steady camera with lights underneath. Sand or a special plastesine covers the glass and the animation is drawn directly on the sand or plastesine. Wherever the material gets thinner, it becomes more transparent letting the light pass through.
For each frame shot, the animator transforms the whole image or redraws parts of it. It is a very difficult technique, because the movements cannot be easily controlled and mistakes cannot be easily corrected.