Creating a Biped
Creating a hierarchical skeleton that is used to control the animation of the mesh skin that is draped over it is quite easy when you create a biped. The skeleton can be set to be invisible in the final render and exists only to make the process of animating easier. Although Max includes a robust set of tools that can be used to create a skeleton of bones, the Biped feature automates this entire process using prebuilt skeletons.
| CROSS-REF | For some characters, manipulating a biped is more work than building a custom skeleton. For these occasions, you can manually create a skeleton structure. Building a skeleton system by hand is covered in Chapter 39, "Understanding Rigging and Working with Bones." |
To create a biped, simply select the Create 
Systems 
Biped menu command and drag in a viewport. The Biped menu command accesses the Biped button found in the Systems category of the Create panel. Figure 42.1 shows a default biped created by dragging in a viewport.
Figure 42-1: The default biped includes all the basic body parts for a human character.
The Create Biped rollout includes two creation methods: Drag Height and Drag Position. The Drag Height creation method lets you set the height of the biped by dragging in the viewport, and the Drag Position creation method creates a standard-sized biped and lets you position it by dragging about the viewport.
| Note | To precisely position a biped on the surface of any existing object, enable the AutoGrid option at the top of the Object Type rollout. |
In the Root Name field, you can name the biped. Every biped bone is given a unique name, and this root name is attached to the front of the unique bone name. For example, if you specify Gloop as the root name, then the right calf bone is given the name, Gloop R Calf.
Below the Biped Name field is the Body Type drop-down list. In this list, you can select from Skeleton, Female, Male, and Classic body types. The differences among these body types relate to the size and shape of the bones. The Classic body type was used in previous versions of Character Studio and exists for backward compatibility. Figure 42.2 shows each of these body types.
Figure 42-2: The four available body types include Skeleton, Female, Male, and Classic.
By default, all biped bones are color coded, with all bones on the right side colored green and all bones on the left side colored blue. The pelvis, which is the root bone, is colored yellow, and the head is light blue. These colors help keep the different bones straight, and the same colors are used for the footprints that define the biped's motion.
Customizing a biped
Although the standard biped resembles a human form, you can use the settings in the Create panel to radically change the biped to resemble whatever creature you've created.
Customized biped skeletons can be saved using the Save File button found in the Motion panel when Figure Mode is enabled. Biped files are saved with the .fig file extension. Saved biped files can then be recalled when a new biped is being created using the Open Fig File button in the Create Biped rollout. You can also select to create any new bipeds using the user interface settings or using the Most Recent .fig File.
| Note | The Save File button saves the skeleton structure as a .fig file when Figure Mode is enabled and saves the animation sequence as a .bip file when Figure Mode is disabled. |
The Create Biped rollout includes settings for toggling the arms on and off. Settings are available for controlling the number of links used to represent all the various body parts listed in Table 42.1. These same settings are available in the Structure rollout of the Motion panel, which is available when Figure Mode is enabled.
| Body Part | Link Limits |
|---|---|
| Arms | On or Off |
| Neck Links | 1 to 25 |
| Spine Links | 1 to 10 |
| Leg Links | 3 to 4 |
| Tail Links | 0 to 25 |
| Ponytail1 Links | 0 to 25 |
| Ponytail2 Links | 0 to 25 |
| Fingers | 0 to 5 |
| Finger Links | 1 to 3 |
| Toes | 1 to 5 |
| Toe Links | 1 to 3 |
| Props | Up to 3 enabled |
| Ankle Attach | 0.0 (back of foot) to 1.0 (front of foot) |
| Height | unlimited |
| Triangle Pelvis | On or Off |
| Twist Links | On or Off |
| Upper Arm Twist Links | 0 to 10 |
| Forearm Twist Links | 0 to 10 |
| Thigh Twist Links | 0 to 10 |
| Calf Twist Links | 0 to 10 |
| Horse Link Twist Links | 0 to 10 (Leg links must be set to 4 to use Horse Links) |
Open table as spreadsheet Ponytail links are located on the back on the head and like the arms will naturally hang down when the spine bones are rotated. Tail links extend as expected off the back of the pelvis bone. Enabled Props appear as tall rectangular boxes attached to the hands. Prop1 is attached to the right hand, Prop2 is attached to the left hand, and Prop3 floats on the left side of the body.
Figure 42.3 shows a biped with two ponytails, a tail, and a single prop.
Figure 42-3: This biped includes two ponytails, a tail, and a prop object attached to its right hand.
| Tip | Ponytail objects can be used to represent ears, horns, or a unique haircut that moves inde-pendently of the head. |
The Ankle Attach value lets you move the foot bones relative to the last leg bone so it attaches at the back of the foot (value 0.0) or at the front of the foot (value 1.0). Although the biped height is set easily by dragging in the viewports, you can also set the height using the Height setting. Changing the Height value scales all bones.
The Triangle Pelvis option isn't initially visible when creating a biped, but if enabled, the pelvis consists of two links that extend from the spine to where the leg links are located. This helps keep the leg joints from intersecting directly under the spine. The twist links feature allows body parts to twist during animation. The Twists option needs to be enabled before twist links can be used, and the twist links are frozen by default. For example, if you hold your arm out to the side with your palm facing forward, the ulna and radius bones that make up your forearm are actually rotated 90 degrees.
| Note | The twist links feature, located at the bottom of the Structure rollouts, cannot be animated individually; it can be used only to deform the skin as the body part is animated. |
Modifying a biped
After a biped is created, you may look to the Modify panel to change the biped, but the Modify panel is empty. Don't be surprised: All the controls for modifying a biped are located in the Motion panel. This is because biped deals with animation and not just with modifying structures.
In the Biped rollout of the Motion panel, you see several icons. These icons are described in Table 42.2.
| Toolbar Button | Name | Description |
|---|---|---|
| | Figure Mode | Enables Figure Mode where you can edit the skeleton structure. |
| | Footstep Mode | Enables Footstep Mode where you can animate the biped by placing footsteps to follow. |
| | Motion Flow Mode | Enables Motion Flow Mode where you can create scripts of motions for a biped to follow. |
| | Mixer Mode | Enables Mixer Mode where you can load and save Mixer files. |
| | Biped Playback | Plays the animated biped in the viewport in real time showing only the bones. |
| | Load File | Opens .fig, .bip, and .stp files. |
| | Save File | Saves .fig, .bip, and .stp files. |
| | Convert | Converts footstep animation sequences to freeform animation keys. |
| | Move All Mode | Enables a mode where the biped can be moved along with all its animation footsteps. |
The first icon button of a little character is the Figure Mode button. When this button is selected, the button turns light blue, indicating that you are in Figure Mode, and a Structure rollout appears.
The Structure rollout includes all the same settings that were available in the Create panel when the biped was first created.
In Figure Mode, all bones can be moved, rotated, and scaled as needed to match the required skin mesh. If you look closely at the Biped rollout, you'll notice a title called Modes and Display with a plus sign to its left. If you click this title, several additional buttons appear. The Mode buttons are used to manipulate bones in certain ways and the Display buttons are used to set which biped objects are displayed. The Mode buttons are described in Table 42.3.
| Toolbar Button | Name | Description |
|---|---|---|
| | Buffer Mode | Displays the latest footstep copied into the copy buffer. |
| | Rubber Band Mode | Allows a parent object to be moved without altering its child hand or foot. Typically results in stretching. |
| | Scale Stride Mode | Scales the biped's stride in proportion to the biped's height. |
| | In Place Mode, In Place X Mode, In Place Y Mode | Makes the character go through the keyed actions without transforming its center of mass. |
The second button in the Modes section is used to enable Rubber Band Mode. In this mode, you can move a parent bone without moving its children along with it. For example, if you've positioned the left foot exactly where it needs to be, then in Rubber Band Mode, the upper leg can be moved without affecting the foot's position. This is accomplished by stretching the upper and lower leg bones like a rubber band.
| Note | The Buffer Mode, Scale Stride Mode, and In Place Mode all work with animation sequences and are covered later in the chapter. |
Setting the Biped display options
The Display buttons in the Biped rollout let you show or hide certain items in order to speed up the display in the viewports. These controls become critical when working with crowds of bipeds. The display buttons are explained in Table 42.4.
| Toolbar Button | Name | Description |
|---|---|---|
| | Objects, Bones, Bones/Objects | Shows only the objects, only the bones (which appear as simple lines), or both. |
| | Show Footsteps, Show Footsteps and Numbers, Hide Footsteps | Shows the footsteps, the footsteps with numbers, or neither. |
| | Twist Links | Displays the forearm as a twisted bone. |
| | Leg States | Displays the foot motion type for each step as Move, Slide, or Plant. |
| | Trajectories | Shows the trajectory of the selected bone. |
| | Preferences | Opens the Display Preferences dialog box. |
| Note | Biped body objects are rendered, but bone objects are not rendered. Enable the Bones display option to ensure that the biped body objects aren't rendered along with the skin mesh. |
The Preferences option opens the Display Preferences dialog box, shown in Figure 42.4. Using this dialog box, you can set the options for how trajectories and footsteps are displayed, and you can set playback options.
Figure 42-4: The Display Preferences dialog box lets you set the options for displaying biped elements.
| Note | The Biped Display Preferences dialog box is different from the Preference Settings dialog box. |
Selecting tracks
The Track Selection rollout is helpful as you begin to move bipeds and bones about. Its buttons select the biped's Center of Mass (COM) located at the pelvis root. With these buttons, you can key COM tracks for moving and rotating the biped. The buttons are detailed in Table 42.5.
| Toolbar Button | Name | Description |
|---|---|---|
| | Body Horizontal | Selects the entire biped and constrains its movement to the horizontal plane. |
| | Body Vertical | Selects the entire biped and constrains its movement to the vertical plane. |
| | Body Rotation | Selects the entire biped and allows it to be rotated. |
| | Lock COM Keying | Allows the Body Horizontal, Body Vertical, and Body Rotation buttons to be used simultaneously. |
| | Symmetrical | Selects the symmetrical body part and allows both to be transformed together. |
| | Opposite | Selects the opposite body part and deselects the current one. |
The Body Horizontal, Body Vertical, and Body Rotation buttons let you quickly select and move the entire biped in a horizontal or vertical direction or to rotate the entire biped using the common transform gizmos. Body Horizontal keys are displayed in red, Body Vertical keys are displayed in yellow, and Body Rotation keys are displayed in green. If the Lock COM Keying button is enabled, then multiple COM keying tracks can be selected at the same time.
The Symmetrical button instantly selects the symmetrical body part along with the current selection so that both can be transformed together. The Opposite button selects the symmetrical body part to the current selected bone and deselects the current bone. For example, if the right leg bone is selected, then clicking the Opposite button selects the left leg bone instead, and if the right arm bone is selected, then clicking the Symmetrical button also selects the left arm bone so both are selected together.
Bending links
The Bend Links rollout includes buttons that let you control the rotation and twist of link sets. Table 42.6 lists each of these buttons.
| Toolbar Button | Name | Description |
|---|---|---|
| | Bend Links Mode | Transfers rotation information onto children links to create a smooth rotation. |
| | Twist Links Mode | Allows constrained rotations about the link's local X-axis. |
| | Twist Individual Mode | Allows rotation of a single link without affecting the other links. |
| | Smooth Twist Mode | Propagates the rotation of the first and last links to all links to create a smooth twist. |
| | Zero Twist | Resets the rotation along the local X-axis to 0. |
| | Zero All | Resets the rotation along all local axes to 0. |
The Bend Links Mode button causes all adjacent bones in a series of links to be adjusted in a realistic manner when one of the bones in the series is moved. Figure 42.5 shows two identical bipeds, each with a rotated tail. The third link in the right biped's tail was rotated with the Bend Links Mode disabled; the left biped has the Bend Links Mode enabled. Notice how the entire tail linkage is affected.
Figure 42-5: When links are rotated with the Bend Links Mode enabled, the entire link chain is affected.
The Twist Links Mode button works in a similar manner to the Bend Links Mode, except it applies to twisting links. The Twist Links Mode button smoothly twists the entire link chain regardless of which link is rotated. The Twist Individual Mode allows only the selected bone to be twisted, and the Smooth Twist Mode bases the twisting of the entire link chain on the rotation of the first or last link. The Smoothing Bias moves the greater area of twisting toward the first link with a value of 0.0 and toward the last link with a value of 1.0.
Figure 42.6 shows how the Twist Links Mode works. The left biped has its fifth spine link rotated, and all other links have gradually been twisted resulting in a smooth rotation over the whole spine. The right biped has had the same link rotated with the Twist Links Mode turned off. Notice how all the links above have been rotated and those below haven't.
Figure 42-6: When a single spine link is rotated with the Twist Links Mode enabled, the entire link chain is affected.
Working with postures and poses
The Copy/Paste rollout includes an interface for saving and reusing different postures, poses, and tracks. Sets of each can be saved into collections. This lets you break up all the poses for a certain character into logical collection sets such as standing poses, sitting poses, action poses, and so on. You can switch among these modes using the buttons at the top of the Copy/Paste rollout. Posture Mode records the position and orientation of a single bone object. Pose Mode records the position and orientation of the entire biped object, and Track Mode records the animation of a single bone object.
| Note | The Track button in the Copy/Paste rollout is available only when Figure Mode is disabled. |
New collections are created using the Create Collection button. You can rename the collection by typing a new name in the Copy Collections drop-down list at the top of the Copy/Paste rollout. Collections of postures, poses, and tracks can be saved as files using the Save Collection button and reloaded using the Load Collections button found in the Copy/Paste rollout. All saved postures, poses, and tracks are saved using the .cpy extension. Buttons are available for deleting the current collection or all collections. The Max Load Preferences button opens a simple dialog box with options to Keep Existing Collections and Load Collections when a Max file is loaded.
Postures, poses, and tracks can also be copied to the interface using the Copy button. Once copied, they appear in a preview window, as shown for the selected pose in Figure 42.7. All copied postures, poses, and tracks are saved with the Max file. Snapshots shown in the Preview window can be taken from the viewport, taken automatically, not taken at all, or hidden using the buttons located directly under the Preview window.
Figure 42-7: A Preview window in the Copy/Paste rollout lets you select the exact pose you want to use.
The selected posture, pose, or track may then be pasted to another bone or biped using the Paste button or using the Paste Opposite button to paste it to the opposite, symmetrical bone. When the Paste Opposite button is used in Pose Mode, the biped that receives a copied pose appears facing the opposite direction to the original. For each mode, there are also buttons to delete the current selection or delete all copies.
The Paste Horizontal, Paste Vertical, and Paste Rotate buttons at the bottom of the Copy/Paste rollout let you paste the COM track keys along with the posture, pose, or track. The By Velocity option pastes the biped's position based on the trajectory of its motion. You can also select to auto-key any TCB and IK values using the Default, Copied, or Interpolated methods.
Tutorial: Creating a four-footed biped
Biped means a two-footed structure, so creating a four-footed biped is actually an oxymoron. This tutorial should really be called "Creating a biped that is hunched over so its hands are touching the ground," but that would be too long.
To create a four-footed biped, follow these steps:
-
Select the Create
Systems 
Biped menu command, and drag in the viewport to create a biped. -
In the Create Biped rollout, set the number of Neck Links to 2, the number of Tail Links to 5, and the Ponytail1 and Ponytail2 Links to 1.
-
Open the Motion panel, and click the Figure Mode button in the Biped rollout to enter Figure Mode.
-
In the Bend Links rollout, click the Bend Links Mode button.
-
Select and rotate the lowest spine bone so the upper torso leans forward.
-
Select one of the thigh bones, and click the Symmetrical button in the Track Selection rollout to select both thigh bones. Then rotate the thighs to come forward toward the head.
The lower legs will follow.
-
Select one of the lower leg bones, and click the Symmetrical button in the Track Selection rollout. Then rotate the lower leg bones backward until the feet are in the same vertical position as the hands.
-
Select one of the ponytail links, and move and rotate it to the position of an ear. Then repeat for the other ponytail link. Make sure that the green ponytail link is on the left side, and the blue one is on the right.
-
With the Bend Links Mode button selected in the Biped rollout, select and rotate the top tail link away from the body.
-
Open the Copy/Paste rollout, click the Create Collection button and select the Pose button. Then click the Copy Pose button to add the pose to the list. Then click the Save Collection button, and save the file as
Cat pose.cpy.
Figure 42.8 shows the resulting cat pose.
Figure 42-8: This cat pose was created by manipulating the biped bones.
