Animating a Multi-legged Character

Animating a Multi-legged Character

Adding Extra Limbs

 

Autodesk 3ds Max Tutorials > Character Animation Tutorials > Biped Beyond the Basics > Animating a Multi-legged Character > 

Animating a Quadruped

In this lesson, you'll animate a four-legged character, a beetle, that leaps on all fours, but can also walk upright on two legs. You’ll lock the hands and feet at certain keys so you can adjust the biped’s center of mass and spine to create the basic poses.

Set up the lesson:

• Open cs4_tut_quad01.max.

  This is the biped used for the beetle.

  

  

  The beetle and its biped

  The beetle walks upright through most of the animation, but in this shot, he’ll move on all fours. Because he's a two-legged character pretending to move like a horse, you won't change him to a horse pose in Figure mode. Instead, you'll use freeform animation to put him into his initial riding pose at frame 0.

Save a FIG file:

1. Select any part of the biped, then open the Motion panel.
2. In the Biped rollout, turn on Figure Mode.
3. Use Save File to save a FIG file of the biped as mybeetle1.fig.

   This preserves the beetle’s original pose.

4. Turn off Figure Mode.

   The pose does not change, since the beetle isn’t animated in this file.

Rotate the legs to put the beetle on all fours:

1. Turn on Auto Key.

   You’ll use Auto Key instead of Set Key for the first pose.

2. On the Track Selection rollout, turn on Body Rotation.

   This selects the center of mass (COM) and activates Rotate.

   

3. Watch the Left viewport, and rotate the center of mass approximately 80 degrees on the Y axis, so the biped is nearly horizontal.

   

   The COM (Bip01) rotated

   The next steps rotate the arms and legs into position.

4. In the Left viewport, draw a small selection box through the middle of the thighs.

   This selects both thighs in a single move.

   

5. Rotate the thighs approximately 120 degrees about the Z-axis.

   Watch the Z Coordinate Display in the status bar.

   

6. Press Page Down to move down the IK chains.

   This selects the calves.

7. Rotate the calves so they are nearly horizontal, and the feet are behind the biped (about –125 degrees around the Z-axis).

   

   Next, you’ll add a couple of rotations to the arms.

Rotate the arms to put the beetle on all fours:

1. In the Top viewport, select Bip01 R Clavicle. Then, in the Track Selection rollout, click the Symmetrical button to select Bip01 L Clavicle.

   Both clavicles are selected.

2. In the Top viewport, rotate the clavicles about the Y-axis, approximately −40 degrees.
   NoteDo not use the Body Rotation button in the Track Selection rollout, because that button turns on Rotate and also selects Bip01 .

   

3. Press Page Down to select both upper arms.
4. Rotate the arms approximately –90 degrees about the X-axis, so the palms are parallel to the ground.

   

5. Rotate the arms approximately −90 degrees about the Z-axis, so the arms stretch out in front of the biped.

   

6. Rotate the arms about the Y-axis until they hang down.

   

   Left viewport view of arms rotated down

7. In the Front viewport, rotate the arms approximately 20 degrees about the Z-axis so they move away from the body a bit more.

   

   Arms moved away from the body

8. Press Page Down twice to select the hands.
9. In the Left viewport, rotate the hands about the Z-axis so they are parallel to the ground (about –90 degrees).

   

10. Rotate the head up, so the biped is looking straight ahead instead of downward.

    

    Head rotated up

11. Rotate the toes so they are flat on the ground. If necessary, rotate the feet, then the toes, so the feet and toes point forward. Watch the Perspective viewport as you rotate.

    Make any additional adjustments to the legs, arms, spine, and so on, until your model resembles the one illustrated in the four views that follow.

    TipLook at the beetle from several views, and rotate around it in the Perspective viewport to help when making the arm and leg rotations.

    

    

    

    

    Four views of the beetle's final pose on all fours

    If the beetle’s posture is incorrect, open cs4_tut_quad02.max to compare.

Change Dynamic Blend and Balance Factor:

For a beetle traveling on all fours, or before you begin any freeform animation, you need to turn off Balance Factor and Dynamics Blend. These settings add secondary motion to footstep animation, which assumes the biped is walking upright.

1. Open cs4_tut_quad02.max.
2. Select any part of the biped, and open the Motion panel.
3. In the Track Selection rollout, click the Body Horizontal button.

   This automatically selects the center of mass, and activates Move.

4. On the Key Info rollout, expand the Body bar. Change the Balance Factor from 0 to 1.

   In the Left viewport, the center of mass jumps from the pelvis to the area under the chest.

   

5. Change the Balance Factor to 2.

   The center of mass jumps to the area under the throat.

   

   Balance Factor=2.0

6. Change the Balance Factor back to 0. (In this file, the Balance Factor was already set to 0.)

   This ensures that the hips and spine balance around the pelvis area.

   

   Balance Factor=0

7. In the Track Selection rollout, turn on Body Vertical.
8. In the key info rollout, set Dynamics Blend to 0.

   Dynamic Blend controls the amount of gravity in an airborne period. Here, we are setting the value to 0 to eliminate gravity calculation and produce a more flattened motion.

   

   TipYou can also access Balance Factor and Dynamic Blend from track bar keys for Body Horizontal and Body Vertical. To do this, right-click the key and choose Controller Properties > Horizontal or Vertical. You’ll find Balance Factor at the bottom of the Body Horizontal key dialog, and Dynamics Blend at the bottom of the Body Vertical dialog.

   For another tutorial that teaches about Balance Factor, see Creating the Illusion of Weight .

Add a ground plane:

In the lesson Animating a Freeform Walk Cycle , you set keys that locked the feet to the ground. Those keys locked the feet to the world, rather than to an object.

In this lesson, you’ll create a box, and then lock the beetle’s feet to the object, instead of locking them to the world.

1. In the Top viewport, zoom out so the biped is smaller.
2. In the Create panel, choose Box.
3. Create a box beneath the beetle. In the Top viewport, start at the top left and drag down to the lower right. After you click, continue to drag down to create a negative height for the box.

   Change the size of the box to 500 units in length, 150 units in width, and –10 in height.

4. Move the box so the biped is at the top end of the box.

   

   Biped at the end of the box

   At this point, don't worry about the biped floating above the box. You'll remedy that next.

5. In the Left viewport, select any part of the biped.
6. On the Motion panel, in the Track Selection rollout, turn on Body Vertical.
7. Press Alt+W to maximize the Left viewport.
8. Move the biped down so its hands and feet are in contact with the box. Zoom in to see the effect. Adjust the bipeds hands and feet if they're uneven.

   

   Biped positioned on box

9. Save the scene as MyQuad01.max.

Lock down the hands and feet:

1. Open cs4_tut_quad03.max.

   This file is like the one you’ve been working on, but the feet have been rotated so the heels are flat on the ground.

2. Turn on Auto Key.
3. Change the Perspective viewport to Wireframe. Zoom in so you can see the hands and feet.

   

4. Press the H key and select Bip01 R Foot.
5. On the Motion panel, in the Key Info rollout, click Set Key.

   The pivot point is on the ball of the foot. You can leave it there.

6. In the Key Info rollout, expand the IK bar. Click the Select IK Object arrow button, and then click the box in the front viewport.

   The name Box01 is displayed in the field next to the arrow button.

   

7. In the Key Info rollout, click Set Sliding Key.
8. In the Track Selection rollout, click the Opposite button.

   The Bip01 L Foot is selected.

9. In the Key Info rollout, click Set Key.

   This sets a key for the left foot.

10. Click the Select IK Object arrow, and click the box again.
11. Click Set Sliding Key again.

    The feet are now locked to the box.

    WarningYou must set the Object Space Object before you set an IK Key. Otherwise, the IK key parameters will be reset to IK Blend of zero and Body Space on. Also note that you can define only one Object Space Object. You cannot keyframe from one Object Space Object to another.
12. Repeat the steps you used to lock the feet with the left and right hands.

    The hands and feet act the same. Both are locked and do not pass through the box.

13. Turn off Auto Key.
14. Check the finished result. In the Track Selection rollout, click Body Vertical, and move the center of mass up and down.

    The knees and elbows bend with the movement. The feet and hands don’t go through the box as the biped is moved down.

    

    

    Knees and elbows bend without going through the box.

Add anticipation:

Before a character jumps, you need to prepare for the jump. To show anticipation, a character moves in the opposite direction from the jump, and holds the pose, as if to tell the audience that something is about to happen.

1. Turn on Auto Key. Move the time slider to frame 10.
2. In the Track Selection rollout, click Body Rotation.
3. In the Left viewport, rotate the center of mass so the chin is almost touching the ground (about 20 degrees around the Y-axis).

   

4. Click Body Horizontal. Move the center of mass back so the elbows lower almost to the ground.

   

5. Select the head. Rotate the head so it’s looking up.

   

6. Add extra rotations to the Spine objects so the spine arches.
7. Raise the center of mass if the elbows pass through the box.

   

   Pose at frame 10.

8. Move the time slider back and forth between frames 0 to 10, and observe the motion.
9. Save your work as MyQuad02.max.

Continue the motion:

You’ll continue the motion at frame 20. You’ll adjust the timing after you get all the poses in place.

1. Move the time slider to frame 20.
2. In the Track Selection rollout, click Body Vertical.
3. Lower the center of mass so the beetle crouches down.

   Don't worry about the elbows moving through the box. You'll fix that in the next few steps.

   

4. Press the H key and select the four biped spine elements (Bip01 Spine through Bip01 Spine03).
5. Rotate the spine links about –15 degrees around the Z-axis.

   

6. Continue individually rotating each spine link until they match the following illustration.

   

   Pose at frame 20.

7. Save the scene as MyQuad03.max.

Next, you’ll animate the pivot points and rotate the feet so they roll from the heel to the toe. You’ll rotate the hands so they rock from wrist to palm to fingertips.

Rotate the feet to prepare to leap:

1. With Auto Key still on, move the time slider to frame 23.
2. Select Bip01 R Foot.

   The foot is selected, and the pivot (large red dot) is displayed at the ball of the foot.

   

3. In the Key Info rollout, click Set Sliding Key.
4. Rotate the foot, so the heel is raised (about –25 degrees around the Z-axis.
5. Go to frame 0.
6. In the Key Info rollout, expand the IK bar. Set Ankle Tension to 1, and then click Set Planted Key.

   

7. Go to frame 27.
8. Click Set Planted Key again.
9. In the IK expansion bar, click Select Pivot, and then select the pivot at the front and center of the toes. You may have to zoom in to see it.

   

   Selecting the pivot automatically sets a key for it. You don’t have to choose Set Planted Key again.

10. Turn off Select Pivot.
11. Move the time slider to frame 30 and rotate the foot.

    The foot now rotates off the toe.

    

12. In the Track Selection rollout, click the Opposite button. Repeat the previous steps for the left foot.

Rotate the hands to prepare to leap:

1. Move the time slider to frame 23.
2. Select Bip01 R Hand, and click Set Planted Key.

   The right hand is selected, and the pivot is displayed and locked at frame 23.

3. Rotate the hand approximately –40 degrees about the Z-axis so the heel of the palm is raised.

   Unlike the toes. the fingers rotate downward. You’ll have to rotate the fingers to correct this.

   

4. Press H and select Bip01 R Finger1, then rotate it upward about –45 degrees on the Z-axis, so it doesn’t go through the surface of the box.

   Since Auto Key is still on, you don’t have to set keys for the fingers after you rotate them.

5. Press Page Up to select the right hand again. Move the time slider to frame 27, and click Set Sliding Key.
6. Turn on Select Pivot. Select the pivot in the front and center of the fingers.

   

7. Turn off Select Pivot.
8. Rotate the hand approximately 40 degrees about the Z axis.

   

   The hand rolls up, with only the fingertips touching the ground.

   TipIf the hand doesn’t rotate around the new pivot, reassign Box01 as Object Space Object and rotate again. Then it will work properly.
9. On the Track Selection rollout, click the Opposite button. Repeat the previous steps for the left hand.

Move the body to prepare to leap:

After both feet and hands are adjusted, the body needs to be moved in preparation for the leap.

1. Move the time slider to frame 30.
2. On the Track Selection rollout, click Body Vertical.
3. Move the biped up.

   

4. On the Track Selection rollout, click Body Horizontal.
5. Move the biped forward.

   

6. Continue using Body Vertical and Body Horizontal until your biped matches the following illustration.

   

   Pushing-off pose.

7. Save your work as MyQuad04.max.

Position the legs for flight:

When the beetle sails through the air, you’ll use free keys on the hands and feet. No IK Blend is needed.

1. Make sure Auto Key is on. Move the time slider to frame 40.
2. With Move or Rotate active on the main toolbar, select a hand or foot.
3. On the Key Info rollout, click Set Free Key. Repeat these steps to set a free key for each remaining foot and hand.

   If you open the IK expansion bar, you'll see that the IK Blend is set to 0 at frame 40 for the extremities.

4. In the Left viewport, use Body Horizontal and Body Vertical to move the center of mass up and to the right.

   The hands and feet are now off the box and the biped is in the air.

5. Select Bip01 R Foot, and move it so the legs extend fully.

   

6. Click the Opposite button. and extend the left leg in the same way.

   

   The knees are no longer bent.

7. With the left foot still selected, click the Symmetrical button to select both feet, then rotate them downward and backward.
8. Press Page Down to select the toes and rotate them as well.

   

   The legs and feet are fully extended.

Position the arms and torso for flight:

Now that the legs are positioned, you'll work on the arms.

1. Select both of the hands, and rotate them downward and backward.
2. Press H and select Bip01 R Finger1 and Bip01 L Finger1. Rotate them down and back.

   

3. Select and rotate Bip01 Spine (the first spine object) so the biped straightens up.
4. This step removes the swayback appearance. Rotate each spine link individually. Go up through the spine, rotating each link, then rotate the first spine link again, if necessary.
5. Rotate the head so the beetle looks ahead.

   

   Final pose of the biped springing into the air.

6. Save the scene as MyQuad05.max.

Pose the upper body to reach the apex:

The character is airborne. As he reaches the apex of his jump, you’ll rotate the spine to hunch him over, tuck his elbows back, and bend his knees.

1. Make sure Auto Key is on. Move the time slider to frame 56.
2. Open the Motion panel if it's not already open.
3. In the Track Selection rollout, use Body Horizontal and Body Vertical to move the biped up and over to the height of his jump.

   Zoom out in the Left viewport so you can see the entire box. This will let you gauge how high the biped should go so it has room to land.

   

   Center of mass moved to apex of the jump.

4. Select Bip01 Spine and rotate it so the biped bends forward.
5. Continue selecting and rotating the spine links so the back forms an arch.

   

6. Rotate the head forward so the biped looks like he's spotting where he will land.

   You might also want to rotate the neck links to create a more fluid bend between the spine and head.

7. Select the right upper arm, Bip01 R UpperArm. Click the Symmetrical button so both upper arms are selected.
8. Rotate the arms back so they are closer to the biped's chest (approximately 40 degrees about the Z-axis).

   

9. Press Page Down to select both biped lower arms. Rotate them forward so the fingers are near the biped’s chin (about –150 degrees around the Z-axis).

   

10. Save the scene as MyQuad06.max.

Pose the lower body to reach the apex:

Now that the upper body is set, continue to the lower body.

1. Select the right calf, Bip01 R Calf. Click the Symmetrical button so both calves are selected.
2. Rotate the calves so the feet kick back.

   

3. If you like, press Page Down to move the selection through the feet and toes, and then rotate them so they tuck under the tail a little.

   

   Final pose of the biped at its maximum height

4. Save the scene as MyQuad07.max.
   TipWhen doing character animation, you can never save too often.

Pose the upper body for the descent:

You’ll continue by choreographing the biped’s descent to the ground.

1. Make sure Auto Key is still on. Move the time slider to frame 72.
2. In the Track Selection rollout, use Body Horizontal and Body Vertical to move the biped down and further to the right.

   

3. Click Body Rotation. Rotate the biped downward until the biped‘s shoulders are pointing at the ground.

   

4. Select only Bip01 Spine2 and rotate about the Z axis until the biped’s back straightens.
5. Select both hands and move them so they are outstretched and ready to break the fall.

   You can position the limbs using forward rotations, or with inverse kinematics moves (as you just did with the hands).

   

   Arms extended to touch the ground.

Pose the lower body for the descent:

In preparation for landing, the legs should curl down to meet the ground after the hands make initial contact.

1. Select Bip01 R Thigh. Then click the Symmetrical button so both thighs are selected.
2. Rotate the thighs approximately 90 degrees about the Z axis.

   

3. Press Page Down to select the two calves of the biped.
4. Rotate the calves in toward the thighs (about –25 degrees around the Z-axis).

   

5. Press Page Down again to select the biped's feet.
6. Rotate the feet in toward the calves (about 115 degrees around the Z axis).

   

7. If you want to fine tune the character, rotate the toes, tail, neck, and head to match the illustration.

   

8. Save the scene as MyQuad08.max.

Create the landing pose:

The beetle will land at frame 75. You’ll lock down the hands and adjust the center of mass.

1. Continue from the previous procedure. Move the time slider to frame 75. Once again, make sure Auto Key is on.
2. In the Track Selection rollout, use Body Horizontal and Body Vertical to move the center of mass so the hands move through the box.

   

3. Select the right hand, and click the Symmetrical button so both hands are selected.
4. Rotate the hands forward so the hands are visible and flat against the ground.

   

5. Select the right hand, and set a sliding key from the Key Info rollout.

   Now you can set a key to lock the pivot.

6. Open the IK expansion bar, click Select Pivot, and then click the pivot (the large blue dot) at the wrist.
   TipYou might want to Region Zoom around the hands in the Top viewport for selecting the pivot.
7. Click the Opposite button to select the left hand, and set another sliding key.
8. Click Select Pivot again, and click the pivot for the left wrist.

   Now both hands are locked to the ground at frame 75.

9. Select both feet. Move them outward and up so the legs extend behind and above the biped.
10. Rotate the feet so the toes point skyward.

    

    The biped prepares for impact; the landing pose completed.

11. Move the time slider back and forth and watch the motion.

    You’ve created a little kick with the legs.

12. Save the scene as MyQuad09.max.

Adjust the arms to create the landing:

Next you'll bend the arms so the impact is absorbed as the beetle lands.

1. Continue from the previous lesson. Move the time slider to frame 83.
2. In the Left viewport, move the center of mass down and right so the elbows are close to the ground.

   The hands are locked to the box and the elbows should bend in response to the movement.

   

3. Move left hand slightly behind the right hand.

   This makes it look like the hands are hitting the ground independently.

   

   The hands don’t land together.

4. Rotate the left hand up so it's parallel to the ground.

Adjust the legs to create the landing:

1. Select both thighs. Rotate them so the legs are under the biped.

   

2. Press Page Down to select both calves, then rotate them so the feet prepare to contact the ground.

   

3. Press Page Down and rotate the feet so the balls contact the ground.

   

4. Press Page Down and rotate both toes until they are nearly horizontal.

   

5. Select the right foot and move it back and slightly up.

   

   When an animal lands, its feet don’t hit the ground at the same time.

6. Rotate Bip01 Spine1 to raise the elbows and upper body slightly.

   

   Hitting-the-ground pose.

7. In the Front viewport, select both calves and rotate them about 45 degrees around the X axis.

   

8. Select each foot and move it in to match the illustration.

   

9. Select both feet. Move the time slider to frame 80.
10. Move the feet so the beetle compresses as he lands.

    The feet should be tucked under the tail.

    

Create the last pose:

1. Move the time slider to frame 86.
2. Select the right hand, and click Set Planted Key.
3. Click the Opposite button. Click Set Planted Key for the left hand.
4. Select the left foot, and set a planted key.

   The left foot is already on the ground.

5. Click the Select Pivot button, and set the pivot to the ball of the foot.
6. In the Track Selection rollout, use Body Vertical to move the biped so the right foot touches the ground.

   

7. Select the right foot, and set a planted key.
8. Click the Select Pivot button, and set the pivot to the ball of the foot.
9. Make minor adjustments to the legs, spine, neck, and head to match the illustration.

   

   Last pose

10. Save your work to MyQuad10.max.

Adjust the timing:

The takeoff and landing are too slow. Use the keys in the track bar to improve the timing.

1. Continue from the previous lesson, and select the entire biped.

   The keys displayed in the track bar are the keys for the entire animation.

   There is too much time between frames 30 and 40.

2. Turn off Auto Key. Select the keys from 72 through 100 by dragging a selection rectangle around them in the track bar.

   

3. Slide the selected keys so the key that was at frame 72 is now at frame 60.

   

   Note the readout on the status bar showing you information about how the frames are being shifted.

4. Now select the keys from frame 40 through the end of the animation.
5. Slide these keys so the key that was at frame 40 is now around frame 33.
6. Move the time slider back and forth.

   The take off and landing is much quicker.

7. Save your work as MyQuad11.max.