Ub Iwerks adapted xerography to eliminate the hand-inking stage in the animation process by printing the animator's drawings directly to the cels. The first animated feature film to use this process was One Hundred and One Dalmatians (1961), although the technique was already tested in Sleeping Beauty (for the animation of the rocks falling and turning into bubbles), released two years earlier. At first, only black lines were possible, but in the 1980s, colored lines were introduced and used in animated features like The Secret of NIMH.[citation needed]