1 首先一個事實：

   Real human motion usually consists footplants,which are periods of time when a foot or part thereof remains in a fixed position on the ground.

  2 Footskate 引入的原因：

   Footskate may be introduced to a motion in several ways。

   Sometimes the raw data itself is imperfect; for example a sensor may be miscalibrated. In such cases the motion can often still be salvaged, but the footplants may be lost in process.

    Footskate can also be added even when the raw data is faithful to the true motion. In standard animation pipelines motion data is usually mapped onto an articulated figure called a skeleton. Since a real human is not rigid,this mapping process can fail to fully perserve footplants.

    Skeleton motion data is often edited in order to adapt to the particular needs of an animation.

    Motion Editing的方法

   Representative editing operations include warping [Witkin and Popovic 1995] , retargeting [Gleicher 1998], path editing[Gleicher 2001],transition generation[Rose et al.1996],and various signal processing algorithms [Bruderlin and Williams 1995] These editing operations fundamentally involve adding only low-frequency changes to a motion, so high-frequency details like crisp footplants are either lost entirely or only approximately perserved.