Biped, Physique, and the Crowd system work together within 3D Studio MAX to provide a complete set of character animation tools. Although these plug-ins can be used in a variety of ways, it is helpful to approach character studio with a basic understanding of how a typical character animation is created.
The following sections provide a brief summary of the basic workflow and related benefits to creating a character with Biped and Physique. You may not use all the following steps, but you're likely to do them in the following order.
Create a basic skin shape for your character using any of 3D Studio MAX modeling tools and surface types. Be sure to place your character's skin in a neutral pose with arms outstretched and legs spaced slightly apart. You may also want to add sufficient detail to your skin's mesh or control points around joints to facilitate deformation during movement.
Note: Since Physique deformations are based on a volume, you can refine your geometry at a later time with minimal impact on your skin behavior. This means you can create your animation before you've built your model if you wish.
Biped automates the creation of bipedal character skeletons. It also lets you introduce significant changes to the skeleton's structure and sizing at any point during your animation without adversely affecting your character's motion. This means you can animate your character without knowing if it is short or tall, skinny or fat. It also means that if the director changes the character's proportions, the animation will still work.
Position the Biped character within its modeled skin. Use Biped's special Figure mode tools to scale bone lengths and to orient the Biped skeleton exactly within the skin's volume. Scale bone thickness as desired to achieve a good initial fit. Then save a figure file, so it's easy to return to this pose.
Use Physique to attach the skin geometry automatically to the biped or a 3DS MAX Bones hierarchy. The attachment is typically made to the root node in the hierarchy: the pelvis object on the biped or the root node on a Bones hierarchy, not the center of mass. The attached skin is deformed as the biped or Bones hierarchy moves.
The links in the Bones hierarchy are used to create a system of 3D envelopes that enclose nearby vertices. Envelopes typically overlap at the parent and child ends of links. Vertices within overlapping envelopes are blended to create smooth skin deformation over joints as the character moves.
Adjust Physique parameters and introduce skin behavior effects to achieve the desired characterization.
Change default envelope shapes by adding cross sections and control points to isolate a more specific volume of vertices for each bone. Or use exclusion lists or per-vertex weighting to apply fine-tuning control over individual vertices.
Introduce bulge angles to change muscle shape based on the angle of a particular joint. Create tendons to simulate the motion of tendons under the skin, based on link movements.
Adjust link parameters to change skin twisting, sliding, and creasing as the biped moves. Sliding allows the skin to compress at the biceps and forearm as the elbow is bent. Twisting controls the amount of skin twisting across a joint intersection.
Create extra links using 3DS MAX bones and dummy objects for added control. Links can be created for the abdominal area to control compression, for example, or to create a link to animate the chest rising and falling as the character breathes. If a character has extra appendages, 3DS MAX Bones can be added to animate them. One common usage is to add a bone to animate the jaw.
Once the skin is attached to a Biped structure, you can freely animate the Biped character and see skin behavior update automatically, based on a current pose. Since Physique skin deformation can slow visual playback of your Biped animation, you can temporarily hide the skin object or reduce its resolution in the modifier stack to improve performance.
You can also choose to develop Biped animations in a separate scene entirely, and apply them to your final skinned character when you are satisfied with your final motion.
A Biped character is essentially an integrated hierarchy of bones that you can position freely using keyframes, IK goals, and footsteps. You can position a Biped character using all the rotation and transformation tools found on the 3DS MAX toolbar.
Many of the 3DS MAX coordinate systems can be used to position the biped. Local coordinates are useful to move a limb along its axis (local X is always the axis along the Biped limb); world coordinates are handy when there is any confusion regarding which way is up. You can use world coordinates as a home base. In 3DS MAX the world Z axis is always up.
Note: Rotations always occur about the local axis.
Biped provides a variety of methods for creating character motion easily. You can start with a purely traditional approach by manually creating keyframes in freeform mode for different poses, letting the computer interpolate between joint positions and IK goals.
You can also choose a partially assisted approach by using footsteps and Biped dynamics to help you create a default walk, run, or jump cycle, and then adjust the biped keyframes and footsteps individually.
When using footsteps, Biped dynamics helps you by simulating gravity and balance.
Gravity can help in a jumping motion to accelerate a character during the falling period and to bend the legs naturally on landing.
Balance adjusts a character's position when the spine is rotated and keyframed to retain a character's balance.
Dynamics can be turned off on a per-key basis or for the entire animation. The animator can override center of mass keyframes created using Dynamics calculation at any time. Simply set the dynamic properties of these keys or chose Spline Dynamics for keys generated by newly created footsteps.
Once you are satisfied with a particular footstep animation and its corresponding dynamic behavior, you can convert it automatically to a freeform animation consisting of a simple combination of keyframes and IK goals. This intelligent conversion gives you control of animation behavior at every frame, for every joint of the character.
Biped Animation Layers offer you a powerful tool for introducing global changes to an existing character animation. For example, by adding a layer on top of an existing run motion, and creating a single keyframe with the biped's spine rotated forward, an upright running motion can be turned into a crouched run. Layered changes can be stacked up, allowing you to refine your motion composition and eventually collapse your layers into a standard non-layered keyframe animation.
In Place Mode is a general tool that you can use to keep your Biped character in view during animation playback. It offers a convenient way of adjusting and adding keyframes to a character without constantly changing your view to follow the character's motion.
Motion capture files can be imported from the .BVH or .CSM formats, edited, and saved as .BIP files. These files can be imported with or without footsteps and dynamics and can be combined in Motion Flow mode with other animations.
You can use the supplied motion capture samples as is or adjust them to suit your needs using Biped's collection of animation tools. The ability to import motion capture marker files directly into character studio using the .CSM file eliminates much of the cost of post-processing optical motion capture data. You can import motion capture files with an additional prop bone, to define the motion of an object such as a sword or club.
Motion Capture Files can be imported with key reduction which makes for more manageable tracks for subsequent editing.
Track View allows you to edit keys and footsteps relative to the animation time line. Periodic motions can be adjusted. If a character nods its head from left to right, you can select all the appropriate head keys and adjust them at the same time using controls in the Biped Multiple Keys dialog.
Footstep editing in Track View allows you to move footsteps in time. If a character needs to jump higher between footsteps, move the landing footsteps further down in time, dynamics automatically compensate by making the character jump higher to keep the character airborne for a longer time period.
You can specify a freeform period in a footstep animation, using Track View. This allows you to take advantage of footsteps and dynamics for part of an animation and switch to manual keyframing during the freeform period. This approach can be particularly useful in animations where there is a mix of animation with the feet are on the ground and then off. Examples of this type of animation include running and diving, or walking and then sitting down.
Keyframe adjustment tools allow you to find the next or previous key for the selected biped body part, use the Time spinner to slide a key back and forth in time, change Tension Continuity and Bias for a key, and to display trajectories.
You can place arms and legs into the coordinate space of another object or the world to simulate interaction with fixed or moving objects. In Freeform mode, for example, putting the character's legs into world space prevents them from sliding or moving when the animator is keyframing the character's center of mass. Putting a character's hand in the coordinate space of a ball allows the hand to move wherever the ball moves.
Many tools in 3DS MAX can be leveraged with character studio. For example, the 3DS MAX Link tool can be used to attach objects to the biped. If a character is mechanical and needs no skin deformation, its body parts can be attached to the biped using the Link tool.
If a character is to pick up and carry an object and then put it down, the Link Controller can be used to animate the duration of the attachment. 3DS MAX bones can be used to animate character sub-assemblies, like pistons, and to create extra links for Physique.
After you have created and modified various animation sequences, and stored them in Biped motion files (.BIP format), you can use Motion Flow mode. This feature allows you to combine various Biped motion files into longer animations that can be quickly previewed and edited. Motion Flow mode automatically places the animations end-to-end, allowing you to mix and match both freeform and footstep-driven motion files. Transitions between successive motions are automatically created for you, to provide a first-pass blending between overlapping frames of animation.
The Motion Flow transitions use velocity interpolation to create seamless transitions between clips. You can use the transition editor to modify a variety of blending parameters, including transition start frame, length, and angle between clips.
Great character animation is a result of many refinements that tune the overall personality of your character. You will find the need to refine progressively both the skinning behavior and the animation timing of your character studio character. Biped and Physique make this iteration process straightforward by fully utilizing 3DS MAX modifier stack and undo methods.
In addition, Biped's ability to map motions between characters makes it very easy to interchange great animations with existing characters, and tune their behaviors to achieve true integration of motion with character motivation and personality.
Once you've created animation sequences for characters or other models (such as a bird flapping its wings), you can replicate the models or characters and apply the motions to these groups using the Crowd system. You can also combine them with a wide range of supplied behaviors to create lifelike activities in crowds, such as people streaming through a doorway, street traffic, or birds and fish flocking and avoiding obstacles. You can use Motion Flow mode to create motion clip networks so that characters perform animation sequences appropriate to their current movement and transition smoothly between sequences. And you can use Crowd's cognitive controllers to transition between behaviors based on a variety of criteria. For more on Crowds, see Overview of Crowd Features.