CAP 211 - Interactive Design and Game Development

Chapter 42 - Creating and Animating Bipeds

Objectives:

This lesson discusses biped objects and their use in animation. Objectives important to this lesson:

  1. Character Studio
  2. Creating and editing a biped
  3. Footstep and Freeform animation modes
Concepts:

biped imageFor this lesson, we will use the material in this chapter through page 990. We will come back for the rest later. As you have already seen, the biped tool is a humanoid skeleton that can be customized to fit characters in 3DS Max. The text gives us some historical trivia, telling us that there was previously an add on to 3DS Max called Character Studio. The features of this add on are now part of the main program. The biped tool is included in this part of the program.

The text reminds us that the biped must be attached to the character mesh with a skin modifier or a physique modifier. The bones of the biped do not need to fit completely inside the character mesh, since the biped can be set not to render, but it is better to size the bones to the mesh first, then to apply the skin modifier. This will require less modification of the envelopes that enclose the character mesh, as seen in the Quick Start chapter.

To create a biped, you can select Create, Systems, Biped, then drag in one of two ways.

  • If you select Drag Height, you should place your mouse pointer where you want the feet of the biped in the Front viewport and drag up or down. This will give you better control over placement and height of the biped.
  • If you select Drag Position, you will create a default size biped when you begin a left click. You can place the biped anywhere you want in the viewport by moving the mouse pointer before you release the left mouse button.

On the modify panel of the biped object, you can name the biped, which will cause all the bones of the biped to inherit that name. By default, each biped you create is numbered and its head is a different color from the last one you made, but they will look a lot alike. Naming them will help tell them apart.

You can also choose from four shapes for the biped: skeleton, male, female, and classic. The text notes that the classic shape was the default in previous versions of the program, and is included to allow the use of older files.

You will have noticed by now that a biped object's right arm and leg are green, and its left arm and leg are blue. This is to help you remember which side is which: there are four letters in left and in blue, five letters in right and in green. These colors are not continued in the fingers and toes of the figure.

We can also observe that the pelvis bone is a shade of yellow because it is in the center or middle of the figure (six letters). The pelvis structure is the root bone, the first bone, of the biped.

save file buttonAs you will see in CAP 202 as well, the biped model may be used with non-human characters that are still four limbed. You can modify most aspects of the structure to accommodate bipedal animals, aliens, and fantasy characters. Once you have made such modifications, you can use the Save File button on the Motion panel to save a new .fig (figure) file. The save button is on the Biped rollout of the Motion panel. It has an image of a 3.5 inch disk on it. This button saves a figure file when figure mode is enabled, and saves a biped animation file (.bip) when figure mode is disabled.

You will want to be aware that the Modify panel for a biped is empty. As indicated above, you make modifications to a biped on the Motion panel. The reasoning given is that a biped is not just a structure, but a structure that is intended to be animated. Look at the Motion panel with a biped selected to see the choices presented in the next image.

biped links list The text provides a chart of the number of links that you can use for each body part that can have them. The spine, for example has four links by default, but it may have as few links as 1 or as many as 10. In the Body Type section of the Create Biped rollout, shown on the right, you see that arms can be turned on and off. By default, the biped, as shown above, has only one finger on each hand, one toe on each foot, and no tail or pony tail.

You can modify all of these parameters before you create your biped. You can also turn on the three props. Prop 1 will attach to the right hand, prop 2 will attach to the left hand, and prop 3 will float on the left side of the body. (Is that your parrot, Mr. Cotton, or are you just happy to see me?)

Note, also, the default value of the Ankle Attach field. A value of 1 would attach the ankle at the front of the foot, and a value of 0 would attach it at the back of the foot. The default value (0.2) is a more average human location.

In addition to the Save File button shown above, the Biped rollout has eight other buttons that are explained in a table in the text. Clicking any of the mode buttons changes what other rollouts are available on the panel. At this point you will want to know the following:

  • Figure mode - allows you to save a figure file, and allows you to edit the bones of your biped
  • Footstep mode - allows you to animate the biped by placing footsteps on the scene
  • Move all mode - allows you to move the biped and its footsteps, allowing you to keep the animation, but change where it takes place

There are four mode buttons and six display buttons hidden behind a plus sign below the buttons shown on the image of the Biped rollout above. (Just to the left of the words "Modes and Display") Expanding this plus sign gives you access to these buttons. The mode buttons are covered in a few pages. The display buttons turn visibility on and off for features. The text warns us that we will have to do this to work with crowds. (We will consider crowds in another lesson.)

As is common for this text, the next several pages are too dry to absorb without examples. Let's consider them after we do a tutorial.

Tutorial Notes and Questions

Tutorial 1 (Creating a four footed biped):

  1. The text admits that this is strange name for the tutorial. Consider it a model for creating a gorilla or other life form that uses its forelimbs for movement. Use the image on page 984 as a guide to your final product.
    Create
    a default biped as instructed.
  2. Set the number of neck, tail, and pony tail links as instructed.
  3. Select Figure Mode on the Motion panel (if it is not already selected).
  4. Turn on Bend Links.
  5. Rotate the lowest spine bone as instructed. Be careful to rotate only as needed, to place the hands near the floor of the scene. Watch the curve of the spine to see where to stop. (Undo is our friend.)
  6. Select both thigh bones as instructed.
    Question 1: What does the Track Selection rollout allow you to do here?
    Question 2: Why do the lower legs follow the thighs?
  7. Modify the lower leg bones as instructed.
  8. Modify the pony tails as instructed. Note that they have bilateral symmetry, so they are green and blue.
  9. Modify the tail as instructed. Note that you only have to modify one bone.
    Question 3: What effect would you get if Bend Links mode was not engaged?
  10. Create the collection, copy the pose, and save the file as instructed.

The text moves on to animating a biped. We are informed that we can use Footstep mode (for walking, running, jumping), Freeform mode (for any other motion), or use both in the same animation.

Footstep mode allows us to place a series of footprints on the scene for the character to follow.

For walking:

  • the Walk Footstep parameter controls how many frames will show the biped's foot in each position
  • the Double Support parameter controls how many frames are used each time both feet are on the ground (like a follow-through for the last step and an anticipation for the next)

For running and jumping:

  • the Run Footstep and 2 Feet Down parameters control how many frames will show the biped's foot in each position
  • the Airborne parameter controls how many frames are used each time both feet are in the air

Each time you click a footstep, it is the next foot in rotation.
Question 4: According to the text, how can we control which foot to begin a walk with?
Question 5: Creating footsteps does not set animation keys. What do you do to set keys for footsteps?
Question 6: Which button illustrated on page 985 gives you a way to make a uniform series of footsteps?

Tutorial 2 (Making a biped jump on a box):

In the second tutorial, you use several of the animation tools described above. You will create a box that a biped will walk, run, and jump onto.

  1. In a new scene, create a box. A pizza box shape will do.
  2. Create a new biped a short distance away from the box. (The ideal distance will depend on how many steps it will walk and run before it jumps.)
  3. Activate Footstep mode as instructed.
  4. Click Walk, Create Footsteps, and make four steps. (Review the previous page to select the Right foot as the first step.)
  5. Click Run, Create Footsteps (Append), and make four running steps. (The character's stride should be longer when running.)
  6. Click Jump, Create Multiple Footsteps, and choose two on the dialog box.
  7. Note that you have to change the altitude of the two footsteps that jump onto the box. (You may need to move the box as well. If you do, you will need to select the biped object to get access to the footsteps again.)
  8. Click Create Keys for Inactive Footsteps. Note that you will not see keys on the timeline.
  9. Run the animation as you normally would. You will see that it was quick and easy, but not very convincing.

Four more pages until the end of this section.

In case you wondered where the Freeform mode button was, the text tells us that we are in Freeform mode when no other buttons on the Biped rollout are selected. Turn off the Footstep mode button in the scene you were just working on and you will see the Key Info rollout appear. This rollout is where you will set and delete animation keys for the biped. There are several more sub-rollouts as well, no doubt a holdover from the Character Studio.
Question 7: What are the names of the Key Info sub-rollouts?

When using Freeform keys for a biped, you will use the timeline as in other animations, and you will be able to manipulate the bones in the viewports, like other animations. Unlike other animations, the keys for the biped are set on the rollout, not with the Set Keys button at the bottom of the screen. However, the keys now appear on the timeline (They did not in Footstep mode.) Think of this as being a way to keep the keys on the timeline from being too complicated to use. Every aspect of a character may be in motion in a keyframe, so it makes sense that we animate a complicated system differently than we animate a prop. This reasoning leads to the Keyframing Tools rollout that allows us to separate tracks for various members of the biped.

The next rollout is the Layers rollout. It is possible to layer animations, allowing the animator to concentrate on animating one or more features in each layer, which combine to a complex animation when all layers are enabled.

As was said above, you save biped animation clips as .bip files, by using the Save File button with the Figure mode disabled. In the second image on this page, the Figure mode is disabled.

The Motion Flow mode button opens the Motion Flow rollout which can be used to combine a series of animation clips into a longer animation.