To use freeform animation for feet, yet keep those feet on the “ground” (the 3ds Max ground plane), you can use a system of pivot points and a few different kind of IK keys. This lesson introduces those features.

Set up the scene:

1. Restart or reset 3ds Max.
2. On the Create panel, click (Systems).

Create a biped and load a FIG file:

1. Click to turn on (Biped), and create a biped in the Front viewport.
2. Go to the Motion panel.
3. Turn on (Figure Mode), then click (Load File).

   3ds Max displays the Open dialog.

4. Open the file tut_swimmer.fig. This file is in the folder \sceneassets\animations\.

   The biped takes on new structural elements stored in the FIG file. This simplified figure has one large toe on each foot and one large finger on each hand; its spine contains two segments instead of four.

   

5. Turn off (Figure Mode).
   NoteYou cannot animate in Figure mode.
6. Click (Zoom Extents All).

Set a key:

1. Change the Perspective viewport to Wireframe (press F3) and zoom in so the feet are clearly visible.
2. Select Bip01 R Foot.

   

3. On the Motion panel Key Info rollout, click (Set Key).

   The foot is highlighted in white, and a key appears on the track bar at frame 0. You have just started a freeform animation.

   

   Track bar key at frame 0

Set different types of keys at frame zero:

There are two ways to set character animation keys in 3ds Max. You can use the standard method of keyframing, which involves turning on Auto Key and transforming objects. It is quick and easy, but if you forget that Auto Key is on, you can set keys unintentionally.

The second method uses the Set Key buttons on the Key Info rollout. These buttons set several parameters at once. This is the method you'll use in the steps that follow.

1. On the Track Selection rollout, click (Body Vertical).

   This selects the biped's center of mass, Bip01, and activates the Move tool in one step. You’ve set a key for the foot, but there is a problem. The foot can go through the ground plane. See for yourself in the next few steps.

2. Right-click the Left viewport to activate it without changing the selection set.
3. With the Body Vertical track still active on the Track Selection rollout, move the center of mass down in the Left viewport.

   The biped moves down through the ground plane (as indicated by the grid in the Perspective viewport).

4. Press Ctrl+Z to undo the move.

Set planted keys:

Now you’ll set a planted key. A planted key does three things: It sets IK Blend to 1, turns on Join To Previous IK Key, and also turns on Object Space. Together, these three settings ensure that the foot will not pass through the ground plane.

For more information about IK Keys, refer to the “Key Info Rollout” topic in the 3ds Max Help.

1. In the Perspective viewport, select Bip01 R Foot again.
2. On the Key Info rollout, click (Set Planted Key).

   The red pivot point becomes more pronounced.

   

3. On the Track Selection rollout, click (Body Vertical), and move the biped down in the Left viewport.

   The foot stays on the ground plane, and the knee bends to accommodate the vertical movement of the biped.

   

   Planted foot stays on ground.

4. Press Ctrl+Z again to return the biped to its previous position.

Now you’ve seen the effect of the planted key on the foot. You can use the same Set Key buttons on pivot points for the feet and hands. Next, you’ll replace the key at frame 0 with a new one, changing the pivot point.

Set pivot keys:

1. At frame 0, right-click the Perspective viewport, and select Bip01 R Foot.

   It still has the planted key from before.

2. On the Key Info rollout, open the IK expansion bar and click Select Pivot.

   All pivot points for the foot are now visible as blue and red dots. The pivot at the ankle is red, showing that this is the currently active pivot point.

   TipWireframe mode lets you clearly see and select the pivot points.
3. Click the pivot point on the ball of the foot, at the base of the toes.

   The new pivot point is displayed in red.

   

   NoteYou don’t have to set a key each time you choose the pivot point. However, you should use the Set Key buttons if you want to change the Key parameters.
4. Advance the time slider to frame 5, and click (Set Key).
5. Right-click the foot and choose Rotate from the quad menu. On the main toolbar, make sure that Reference Coordinate System is set to Local.
6. Rotate the foot up approximately –15 degrees about the local Z axis to make the heel raise, and then click (Set Planted Key).

   The heel lifts off the ground, the foot rotates on the ball, and the toes stay on the ground.

   

Now you can animate the pivot point to the toes, as the ball of the foot lifts off the ground.

Animate the pivot points:

1. Drag the time slider to frame 10, and then click (Set Key).
2. Click Select Pivot, and then click the pivot on the end of the toe.

   

3. Click (Set Sliding Key) to set a key for the pivot.
4. Click Select Pivot again, to turn it off.
5. In the Perspective viewport, right-click the foot and choose Rotate from the quad menu.
6. Rotate the right foot about –25 degrees around the Z axis so the heel continues to raise and roll off the toes.

   

7. Click (Set Sliding Key) to keyframe the foot rotation.

   The sliding key does not join to the previous key, but has IK Blend set to 1, which keeps the foot above the ground plane. If you had set a planted key, the foot would jump to a different location as it attempted to join to the previous key.

Save your work:

• Save the scene as walkcycle_beginning.max.