Lesson 5: Changing Footsteps using IK Keys

Footstep and Freeform modes both use the same underlying inverse kinematics to animate the biped skeleton. Footstep gizmos are a method for manipulating sequences of IK keys.

In this tutorial you'll learn how making changes to the IK keys affects the footsteps.


  1. Load cs3_tut03_footsteps_keys.max.

    A biped is displayed with four footsteps in the viewport.

Setting IK Keys to create footsteps

  1. Move the time slider to play the animation.

    The biped hops on his right foot. Notice that there is no footstep for the right foot between footsteps 2 and 3.

  2. At frame 45, select Bip01 R Foot.

  3. On the Motion panel, in IK Key Info menu, click Set Planted Key.

    The pivot point is displayed in the viewport.

  4. Turn on Key mode.

  5. At frame 48, click Set Planted Key.

    The pivot point has been shifted to the toe.

    Note that the lowest IK pivot is selected by default for cases where IK is applied to new keys.

  6. At frame 54, click Set Planted Key.

    The biped is moved back to the ground. A footstep is displayed beneath the biped's foot.

    A footstep has been created, because there is now an interval of time where IK is applied between the two planted IK keys.

Changing the duration of footsteps using IK Keys

  1. At frame 60, click Set Planted Key.

  2. Open Track View.

  3. Turn on Footstep mode, so you can see the Biped Footsteps track.

  4. Notice that Footstep 3 extends for 15 frames from frames 45 to frame 60.

  5. Turn off Footstep mode.

  6. Select Bip01 R Foot.

  7. At frame 63, set another planted key.

  8. Turn on Footstep mode.

    Track View again displays the Footsteps track.

    The duration of the footstep now is 18 frames, from frames 45 to 63.

  9. Turn off Footstep mode.

Removing footsteps using IK Keys

  1. At frame 45, set a free key.

  2. At frame 48, set a free key.

  3. At frame 54, set a free key.

    Note that a vertical key is modified to bring the biped down over its footstep since the liftoff frame for the jump now begins at frame 54 instead of frame 48.

  4. At frame 60, set a free key.

    The footstep disappears.

    There is only one IK key left. With no IK interval defined, there is no duration and therefore no footstep.