Non-Biped Crowds

Motion synthesis lets character studio derive character motion from a combination of crowd behaviors and either motion flow networks, when animating bipeds (see Biped Crowds), or clip controllers, when working with non-bipedal creatures. In the latter case, using the Global Motion Clip and Driver Motion Clip controllers, you can animate groups of creatures such as birds, butterflies, schools of fish, and insects. You can create clip controllers either as block controllers in Track View, or, more directly, with the Crowd helper controls on the Global Clip Controllers rollout.

Two Approaches to Animation

You can animate your creature either in place with looping animation but no transformational motion (such as a bird flapping its wings), or you can incorporate transformational motion into the animation as well (the bird moves upward while flapping its wings). In-place cyclic motion lends itself to flying or swimming motions like birds and fish, while adding lateral motion lends itself to crawling type animation where feet should be planted on the ground and not sliding. Depending on which you use, you toggle options on the Motion Clips tab of the Synthesis dialog. In both cases, you use crowd delegates driven by behaviors to motivate the creatures, which are linked to those delegates.

Note: To animate a model for motion synthesis, apply modifiers to the model and animate their parameters. Modifiers such as Bend, Taper, Wave, and Xform produce animation you can use with motion synthesis. Do not use sub-object animation, such as animation of vertices on an Editable Mesh object.

Cyclic In-Place Animation

First you create a creature with a few short loop cycles, like the beating of wings, gliding, turning left and turning right. This creature is assigned as the Global Object or the master object from which the motion clips will be derived. Then clones of the original creature are created. The clones are positioned and linked to delegates. States are created to select which clips will play based on a state.

For example, if a bird (delegate) is pitching up or accelerating, the fast-beating clip is used; if the bird (delegate) slows to a stop, the wings-at-rest clip is used, and so on. During synthesis, character studio determines which state should be active depending on the speed and direction of the delegates. An active state determines which clip should be applied to the clones of the original object. Clips are blended together to create the animation. Available states are speed, acceleration, pitch, pitch velocity, heading velocity, or script (MAXScript).

Animation with Lateral Motion

For walking multi-legged creatures, you can animate lateral motion as well as the cyclic motion of the legs moving. This is done to ensure that the creatures' feet do not slide as they move. character studio then uses the lateral motion information to create a state that perfectly matches the actual motion. character studio then strips the actual motion out. When a delegate approaches the speed and heading recorded in that state, the appropriate motion clip is triggered. This technique minimizes sliding feet.

Use the Crowd tools to create the initial motion for the delegates. Use a seek or avoid behavior to steer birds, for example. Your object with the loop animation is then copied and the copies are linked to the delegates to create the complete animation. The delegate handles the path and the clip controllers handle the looped animation.

You can create Driver Motion Clip and Global Motion Clip in Track View by assigning a controller to the available controller under Block Control. It is, however, simpler to use the Crowd helper controls on the Global Clip Controller rollout to apply and use the clip controllers.

Global Motion Clip

Global Motion Clips store the clips to be shared among multiple Driver Motion Clips, which are assigned to the cloned objects during synthesis. Global Motion Clips also contain the logic for performing motion synthesis on a collection of objects with trajectories and states associated with clips. Controls for motion synthesis are found in the Synthesis dialog.

The way the motion clip keys are scaled and ordered depends upon user-defined states. Each state contains one or more motion clips that will be played when the state is active.

Driver Motion Clip

Driver Motion Clips are controllers that contain motion clips, or individual clips of animation. These motion clips are sequenced to create animation, and overlap slightly with automatic blending to smooth the transitions between clips.

Procedures

To use Motion Synthesis with non-bipedal creatures:

All of the work involved in copying and synthesizing clips takes place using controls in the Synthesis Dialog. This dialog has three tabs: Motion Clips, State, and Synthesis.

This procedure assumes that the global object is static and has animation that loops. For creatures with many legs, you can animate lateral motion on the global object and then strip out the lateral motion with the Synthesis dialog. This latter approach serves to minimize foot sliding in a multi-legged creature.

Animate an object.
Create animation in one position, like a bird's beating wings. Create a variety of animation like a gliding motion (wings still), wings beating slowly, and so on. To animate the object, apply modifiers and animate their parameters.

This will be the Global object, from which animation clips will be derived.
Using the Create panel (Helpers) Object Type rollout, add a Crowd object and a Delegate object.
Create the objects in the Top or Perspective viewport.
Use the Crowd object (Scatter Objects) tool to clone the delegate and optionally distribute the clones (you can also distribute them manually).
Make sure you end up with an equal number of delegates and animated object clones.

Next, associate and link the objects to the delegates.
On the Setup rollout, click (Object/Delegate Associations).
The Object/Delegate Associations dialog appears.
Add the objects and delegates into their respective columns.
Click Align Objects With Delegates, and then click Link Objects To Delegates, and then click OK to exit the dialog.
The objects align themselves with the delegates and are linked to the delegates.

Next, animate the delegates with behaviors. See Assigning Behaviors for information on using behaviors.

When you solve the simulation, the cloned objects follow the delegates, which are guided by behaviors. You then generate motion synthesis based on the delegate movement.
Select the Crowd object. On the Modify panel Global Clip Controllers rollout, click New, and use the Select dialog to select the Global object from step 1.
The object appears in the Global Clip Controllers rollout list.
In the list, click the object, and then click the Edit button.
The Synthesis dialog displays. Its name is that of the object.
On the Motion Clips panel, turn off all checkboxes in the From Global Object and Remove Local groups.
Use these options only if your original object has lateral motion to coordinate with footsteps.
On the Motion Clips panel, click New.
This opens the MotionClip Parameters dialog, which lets you set the name, color, and frame range for a motion clip.
Choose a descriptive name and a frame range for the motion clip.
For example, frames 0 through 10 might be your glide animation.
Continue to define clips using different frame ranges from the Global object's animation. Give the clips descriptive names.
Next, you define states whose parameters determine when motion synthesis is to use each clip.
Click the State tab, and then click New State.
A new state is added to the drop-down list at the top of the Synthesis States group. Give the state a descriptive name. In many cases, the state can use the same name as the motion clip that's to be associated with it.

Next, you specify the state's parameters; that is, how the delegate should be moving when the associated object is to use its motion clip. For example, your glide motion should be active only if acceleration is less than 0.
Click Edit Properties and define how character studio should activate the clip, based on any combination of speed, acceleration, and so on. Click each appropriate tab, turn on its Use ... checkbox, and set parameters. Click Exit to exit the dialog.
When using a range, make sure the Min setting is lower than the Max setting. For example, when using a negative range such as -180 to -10, enter the number with the higher absolute value (-180) as the Min setting.

You should already have several motion clips. Now you need to associate a clip with this state. For example, if you've defined a state whose acceleration is less than 0, you might associate the Glide clip with it.
In the MotionClips group, click Add Clip, and in the Select MotionClip dialog, highlight a clip and click OK.
Repeat steps 14 and 15 for each state to be used in motion synthesis.
Go to the Synthesis panel, click New Driver Motion Clip, and add all of the cloned objects.
Click Auto Blend All and then click Synthesize All.
The synthesis occurs as a progress bar displays. When the synthesis is completed, the Synthesis dialog reappears. You can now view the ClipState parameters' ranges and average values by clicking State panel Edit properties. This is useful in fine-tuning state properties.

Click OK to exit the Synthesis dialog.
Click (Play Animation). It's not necessary to re-solve the simulation.
The objects follow the delegates and are animated using clips that are activated according to delegate motion and the states you created.