This tutorial is designed for Softimage|3D but it'd work just as well using any 3D animation package.

Rig up a really simple character ready for animation. I like to constrain the position of the feet to the leg end effectors so that I can deal with the foot rotation separately. If they're parented to the end effectors then they'll rotate with the leg, which is frustrating.

Getting a sliding figure,

1 - Change the animation length to be around 200 frames long. Set your start position as below and save Explicit Translation->All key frames at frame 1 for on the hips as well as each of the end effectors.

2 - Move the time slider to frame 20, slide the hips forwards until the front leg becomes the back, then move the back leg forward to compensate and then save Explicit Translation->X key frames for the hips as well as the leg you just moved.

3 - Repeat step 2 for frame 40 so that the character is back at their start pose.

4 - Now if you scrub back and forth with the time slider you'll notice that one leg is sliding rather strangely. This is because that leg should be moving from frame 20 to 40, however it's currently sliding from frame 1 to 40. To fix this open up the Dope Sheet while you have the misbehaving foot selected and examine it's key frames for X translation. Select the key frame currently at frame 1 and with the control key held down drag it to frame 20. Now drag the little white selection icon away and scrub back and forth in the time line. You should now see the character sliding a full 40-frame cycle.

5 - Repeat the steps above until you reach frame 200. You may want to use the Dope Sheet to fix any sliding legs, you can simply copy key frames to keep the feet pauses at the correct points in the animation.

6 - Once you've completed the sliding animation open up the Fcurve window and inspect the X translation curves for the end effectors. You'll notice the curves look a little wobbly, straighten out the pauses by converting certain key frame's interpolation to Linear type (see below).

Animating the hips and legs lifting.

7 - At frame 10 lift up the hips and sliding leg and then save a key frame in Y only. Repeat this step through out the entire animation.

8 - Once again you'll need to either copy key frames in the Dope sheet or insert key frames in the Fcurve window to prevent the feet from slipping.

Animate the hip rotations.

9 - Now key the rotation of the hips in the top view (should be the Y axis), so that the hips rotate back and forth depending on which foot is to the fore. You should find you're setting keys at 1,20,40…etc

10 - In the X-axis key the hips rotating up and down as the feet lift. Again you should find you're saving keys at around 10,30,50..Etc

Complete the Animation!

11 - Now you can key the foot rotations and go through and finesse the animation until you're happy with the walk.

Some notes:
- Remember you can move and scale a group of key frames using tag in the Fcurve window.

- Using the Selectablility function you can prevent objects from being selected in the view ports, meaning you can quickly grab you end effectors and hip controller without zooming in.

- Using Info->Transformation Set-up you can set the default transformations for each object, so you don't need to keep changing your transform selections.

Ben Cowell 2001