Cutout animation is a form of stop-motion animation using flat characters, props and backgrounds cut from materials such as paper, card, stiff fabric or photographs. The props would be cut out and used as puppets for stop motion. The world's earliest known animated feature films were cutout animations (made in Argentina by Quirino Cristiani), as is the world's earliest surviving animated feature Die Abenteuer des Prinzen Achmed (1926) by Lotte Reiniger. The technique of most cutout animation is comparable to that of shadow play, but with stop motion replacing the manual or mechanical manipulation of flat puppets. Some films, including Die Abenteuer des Prinzen Achmed, also have much of their silhouette style in common with shadow plays. Cutout animation pioneer Lotte Reiniger studied the traditions of shadow play and created several shadow play film sequences, including a tribute to François Dominique Séraphin in Jean Renoir's film La Marseillaise (1938). While sometimes used as a relatively simple and cheap animation technique in children's programs (for instance in Ivor the Engine), cutout animation has also often been used as a highly artistic medium that distinguishes itself more clearly from hand-drawn animation. Cutout animation can be made with figures that have joints made with a rivet or pin or, when simulated on a computer, an anchor. These connections act as mechanical linkage, which have the effect of a specific, fixed motion. Similar flat, jointed puppets have been in use in shadow plays for many centuries, such as in the Indonesian wayang tradition and in the "ombres chinoises" that were especially popular in France in the 18th and 19th century. The subgenre of silhouette animation is more closely related to these shadow shows and to the silhouette cutting art that has been popular in Europe especially in the 18th and 19th centuries. While many cutout animation puppets and other material is often purposely-made for films, ready-made imagery has also been heavily used in collage/photomontage styles, for instance in Terry Gilliam's famous animations for Monty Python's Flying Circus (1969-1975). Cutout techniques were relatively often used in animated films until cel animation became the standard method (at least in the United States). Before 1934, Japanese animation mostly used cutout techniques rather than cel animation, because celluloid was too expensive. Today, cutout-style animation is frequently produced using computers, with scanned images or vector graphics taking the place of physically cut materials. South Park is a notable example