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3D DIRECT • November 13, 2000

Walking the Dog with character studio 3

by Michele Bousquet

Discreet has just released the packed character studio 3 plug-in for 3D Studio MAX 3, showcasing a host of new tools for making character animation easier and faster. In addition to the much touted crowd animation tools (to be covered in a future tutorial), major enhancements have been made to freeform animation.

New character studio users sometimes have trouble getting their heads around the whole freeform/inverse kinematic (IK) thing. With character studio 3's new IK controls, commonly used sets of IK parameters can be set at the click of a button, making it easy to get an animation going quickly. For experienced freeform users, character studio 3 has much-longed-for tools such as animatable pivot points and instant pinning of a hand or foot to a previous key.

Even if you've never worked with freeform mode before, this tutorial will show you how to take advantage of these new tools to animate a four-legged character doing a basic walk sequence.

A few words about freeform

Before we get into the meatand bones of this tutorial, let's talk about freeform animation. If you've never used it before, there are a few things you should know.

Any freeform animation can be made to simulate footstep animation by using the controls on the IK Key Info rollout. Select the biped and go to the Motion panel to take a look at this rollout. A few parameters have been added to this rollout for character studio 3. The controls carried over from v2 still perform the same functions as before, and remain useful for the same tasks.

Basically, when you want a foot or hand to stay still, you do these steps:

  • Select any part of the arm or leg
  • Create a key with the Set Key button
  • Set the IK Blend parameter to 1
  • Choose the Object option at the lower right of the rollout

An example would be a foot planted on the floor during part of a walk cycle. If you do these steps, then move the spine or COM, the foot or hand will remain planted while the body moves around it.

When it's time for the foot or hand to move, you:

  • Select any part of the arm or leg
  • Create a key with the Set Key button
  • Set the IK Blend parameter to 0
  • Choose the Body option at the lower right of the rollout

You'd use these settings when the foot moves in space to the next step. If you move the spine or COM, the hand or foot follows along accordingly.

The model

To do this tutorial, download the file Dog.max. This file contains a simple mesh of a happy cartoon puppy with big floppy feet.

Choose Biped from the Named Selection Sets list, and click Yes on the message dialog to unhide it. A biped is bent over and posed to fit the dog mesh. The dog's eyes, ears, and tongue are linked to the biped's head.

Note that this particular biped has been set up with one finger and one toe on each hand and foot, making the model easier to animate. Also note that the spine was made to go up the dog's back by moving and rotating the lowest spine link, not the COM.

Physique has already been applied and adjusted, and should work reasonably well with the biped structure as long as canine limitations are kept in mind.

As a first step, you should freeze the dog parts to avoid moving them by accident when experimenting with the freeform controls. You can select all the dog parts by choosing Dog Parts from the Named Selection Sets list.

New buttons

In character studio v2, you had to set these parameters manually for each part of a walk cycle, which could be time-consuming and frustrating. Then, after all that work, the feet and hands were still inclined to slide around if you weren't extremely careful in setting your keys.

Character studio 3 has a series of new buttons on the IK Key Info rollout that serves three purposes. First and foremost, they create a key and set the IK Blend and Body/Object parameters for you automatically, as with the two scenarios described above. Secondly, one of the buttons sets a new parameter—Join to Prev IK Key. This checkbox forces the foot or hand to match the previous key's position, meaning the foot or hand will not slide between keys—no way, no how. (Did you hear that resounding sigh of relief heard from veteran freeformers?)

The two buttons you will use the most are:

Set Planted Key

IK Blend = 1

Object selected

Join to Prev IK Key checked

What it means: The foot or hand will stay planted even if the spine or COM is moved, and will match the previous key if it is also a planted key.

Set Free Key

IK Blend = 0

Body selected

Join to Prev IK Key unchecked

What it means: The foot or hand can be animated freely, and will also follow along with the spine or COM if they are animated.

There is also a third button, Set Sliding Key, which we'll talk about later in this tutorial.

Animatable pivot points

As the dog's hand or foot passes through the various phases of the walk cycle, you will want him to pivot first on the heel, then the ball of the hand or foot, then possibly the toe. You can animate these pivot points with the Select Pivot button on the IK Key Info rollout.

On any frame with a key for the hand or foot, click Select Pivot to display selectable pivot points as red dots on the hand or foot. Just click the desired pivot point, then click Select Pivot again to turn it off.

Now that you've got the background information, let's get on with making the dog walk using these new controls.

Walking the dog

Since we've got a cartoon dog, we'll make him walk in a cartoon fashion. Opposite arms and legs will move together so he can keep his balance. First we'll get the dog taking some steps, then later on we'll make the movement more natural by animating pivot points.

First, select Set Dog Parts, then hide all selected objects. This will make it easier to work with the biped. Then select any part of the biped and go to the Motion panel.

The first thing to do is get the biped's hands and feet to stay stuck down on frame 0. The Set Planted Key button was made for this. Select any part of an arm or leg, click Set Planted Key, select another arm or leg, click Set Planted Key again, and so on. Planted keys must be set individually for each limb—the Set Planted Key button is disabled if more than one arm or leg is selected.

Next, turn on the Animate button and click Body Vertical. Move the COM up and down to test the settings. The biped's feet and hands should stay put while the body moves up and down. If they don't, then undo any movement you just did and set the planted keys for each arm and leg again. If you've already set keys for a particular limb, setting them again won't cause any damage.

Leave the biped in a slightly crouched position to prepare for the walk. You'll need to leave the Animate button on throughout the rest of this tutorial. You'll also need to set a vertical key for the COM, so click Body Horizontal and click Set Key.

To keep things simple, we'll do each vertical key on frame multiples of 10. This will make a somewhat slow walk cycle that will be easy to control.

  • Go to frame 10. This is the frame where you'll make the biped lift one hand and one foot in the air as part of the first step.
  • Select the left hand, and click Set Free Key. Move the hand upward and forward slightly. By "forward" I mean toward the front of the dog's body.
  • Perform the same procedure on the right foot. Move the COM upward until the standing arm is nearly straight.

Go to frame 20, and move the COM downward and forward. The lifted hand and foot will move with the COM, while the others stay planted down. Move the lifted hand and foot forward and downward to sit on the ground. You might have to rotate the hand to make it sit flat on the ground. Set a planted key for the hand and foot that have just landed on the ground.

You have just made the dog take one step. The same process will be used to make the dog take a second step.

Before going on, we need to set planted keys for the left foot and right hand, which have remained planted all this time, but are about to move. On frame 20, select the right hand and click Set Planted Key. Do the same for the left foot.

Go to frame 30. Select the right hand, click Set Free Key, and move the hand upward and forward. Do the same for the left foot. Move the COM forward and upward until the biped's weight is centered over its body, and the standing arm is nearly straight.

Go to frame 40, and move the COM downward and forward. Place the left hand and right foot on the ground, and set a planted key for each one.

The basic walk cycle is complete. Did you see the pattern here? Set Planted Key is for when the leg or arm sticks to the ground, while Set Free Key is for when the arm or leg moves with the body.

Scrub through the animation to see how it looks. You can also unhide the dog mesh to see it move through the steps.

Next, you'll work on making the feet move from heel to toe on each step with animated pivot points.

Hide the mesh and unhide the biped. Make sure the Animate button is on. Select the biped and go to the Motion panel.

Go to frame 20, where the right foot steps down for the first time. We want to make it come down heel first before placing the entire foot on the ground.

Select the right foot and rotate it. By default, it rotates from the ball of the foot. We want it to rotate from the heel.

  • Click Undo to undo any rotation you just made.
  • Click Select Pivot on the IK Key Info rollout. Each possible pivot point appears as a blue dot. The current pivot point is red.
  • Click one of the pivot points at the heel of the foot to turn it red. Click Select Pivot to turn it off.
  • Now rotate the right foot again. It rotates from the heel, as we'd like it to. Rotate the foot upward a bit.
  • Go to frame 25, and rotate the foot to sit flat on the ground.
  • Next we'll work with the pivot points to animate the left foot taking off from the ground at frame 20.
  • Select the left foot, go to frame 10, and click Set Planted Key. Go to frame 15 and click Set Planted Key again. On frame 15, rotate the foot upward slightly.

Go to frame 20. Click Select Pivot and set the pivot to the tips of the toes. Be sure to turn off Select Pivot before continuing.

Rotate the foot. You may notice, the foot rotates from the middle despite the new pivot point. For this type of movement, a sliding key is needed. This type of key allows the foot to move around while still retaining some of the characteristics of a planted key, such as staying still when the COM is moved.

With the left foot selected, click Set Sliding Key. Note that the Join to Prev IK Key checkbox is now off, so the foot isn't locked to the previous key's position.

Rotate the foot upward. The foot should rotate from the toe.

Only one more thing remains to be done. If you scrub between frames 0 and 10, you will see that the left heel dips slightly below the ground between these frames. You can make the foot stay put by setting the Tension parameter on the Key Info rollout at keys on either end of the dip. With the left foot selected, go to frame 0, and set the Tension parameter to 50. Go to frame 10 and set Tension to 50 there as well. You can use this technique to correct any other areas of the animation where the foot or hand dips.

You have now learned all the tools needed to make a quadruped walk with pivoting, non-slipping feet and hands. Work on the basic walk until it the legs and arms move perfectly, then add details such as head and hip motion. The animation shown below uses the Flex modifier to make the ears flop, and a looping motion on the tongue for a puppy-like pant. The dog wags his tail in celebration of the new and improved character studio 3.

Michele Bousquet is an animator and author specializing in 3D Studio MAX and character studio. She recently authored the character studio 3 Update Courseware for Discreet. This tutorial is condensed from Michele Bousquet's new book Animating with character studio 3, available from her Web site www.maxhelp.com. Dog model created by Ozgur Ustundag.