The article focuses on the problem of generating realistic human motions in realistic character animation. According to the author, as with passive-object simulations, a character's motion needs to be consistent with the laws of physics for an animation to appear realistic. But consistency alone is not sufficient for generating realistic looking animations. To produce natural-looking motion, it's not enough to have just physically correct motion; the intricacies of the character's muscles and bones and how they pertain to motion have to be taken into account. The burden of animation quality rests entirely on the animator. According to him three important areas in realistic character animation still need to be addressed: integrating and applying multiple realistic motion sequences into a single continuous character animation; re targeting motion to different characters while preserving realism; and developing an intuitive interface to the motion-data libraries. INSETS: Human Run and Jump Libraries; Turning Motion into a Spacetime-Optimization Problem.